SUBJECT FORENSIC SCIENCE

Paper No. and Title PAPER No.7: Criminalistics and Forensic Physics

Module No. and Title MODULE No. 1: Crime Scene Management & Investigation

Module Tag FSC_P7_M1

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 1: Crime Scene Management & Investigation
 TABLE OF CONTENTS

1. Learning Outcomes
2. Crime- An Introduction
2.1 What is a Crime?
2.2 What is a Crime Scene?
2.3 Types of Crime Scene.
2.4 Why a Crime is Committed?
3. Crime Scene Investigation
3.1 Crime Scene Team
4. Crime Scene Investigation- The seven Important Stages
4.1 Securing the Crime Scene
4.2 Scanning the Scene
4.3 Sketching the Scene
4.4 Searching for Evidence
4.5 Documentation of Crime Scene
4.6 Securing, Collecting & Packaging of Evidence
4.7 Chain of Custody
4.8 Crime Scene Reconstruction
5. Summary

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 1: Crime Scene Management & Investigation
 1. Learning Outcomes
After studying this module, you shall be able to learn about Crime, Crime Scene, various
types of Crime Scenes, few basic reasons behind the commission of a crime, the crime
scene investigation, Locard’s Exchange principle, who are the members of a Crime Scene
Team, the seven important stages of a crime scene investigation including Securing of
crime scene, Scanning of crime scene, Sketching of the crime scene, Searching of evidence,
Documentation of crime scene, Collection & Packaging of evidence, Chain of Custody and
Reconstruction of Crime Scene.

2. Crime- An Introduction

2.1 What is a Crime?

Crime is an act or the commission of an act that is not allowed or the omission of a
responsibility that is ordered by a public law and that makes the criminal accountable to
punishment by that law.

2.2 What is a Crime Scene?

A crime scene is a place where a crime has occurred (or another place where sign of the
crime may be establish), and includes the part from where maximum of the physical
evidence is retrieved by law enforcement personnel, crime scene investigators (CSIs) or in
occasional circumstances, forensic scientists. Crime scenes may or may not be where the
crime has happened. There are various stages and kinds of crime scenes.
2.3 Types of Crime Scene
A different type of crime scenes includes outdoors, indoor, and conveyance. Outside scene
of crime is the very challenging to scrutinize. The experience with the fundamentals such
as rain, breeze, or heat, as well as animal movement, infects the crime scene and causes
damage to evidence.
Indoor crime scenes have a significantly lower chance of contamination due to lack of
exposure. The contamination here usually comes from the people factor. Conveyance crime
scenes are offences done by means of transport, such as robbery or auto theft. All type of
crime scene, with the nature of the crime done (robbery, homicide, rape, etc.) has diverse
procedures.

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MODULE No. 1: Crime Scene Management & Investigation
 2.4 Why a Crime is Committed?
There are several reasons behind the commission of a crime. A crime may be committed
for the following reasons:-
1. Lure of Money
2. For the sake of Revenge
3. Emotion—love, hate, anger

3. Crime Scene Investigation

An Effective Crime Scene Examination uses a stages of procedure in the detection,
protection and gathering of Physical Evidence. The Corpus Delicti of an offence i.e. “Body
of the Crime” must be clear. At a crime scene, before starting investigation it must be
proved that a crime has occurred as well as the person who is charged with the crime was
accountable for the commission of crime.

The aim of a crime scene examination is to identify, document, and gather evidence at the
scene of a crime. Resolving the crime will depend on joining together the evidence to form
a image of what take place at the crime scene. The first individual to notice this condition
was Dr. Edmond Locard, Director of the world’s 1st forensic laboratory in Lyons, France.

The Locard’s Exchange Principle said that when a individual comes into interaction with
an object or another individual, a cross transfer of physical evidence will occur. The
exchanged substances shows that two objects were in contact.
The 2nd part of Locard’s Principle says that the strength, period and nature of the
constituents in contact decide the extent of the transmission.

3.1 Crime Scene Team

A crime scene team includes

1. Team members
2. First police officer on the scene:- Protects the scene
3. Medics (if necessary)
4. Investigator(s)
5. Medical examiner (if necessary): Declare death, I.D. the body, determine cause,
manner, and time of death.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 1: Crime Scene Management & Investigation
 A Medical Examiner is responsible for Recognize the dead, Found the time and date of
death, Determine a medical cause of death (the injury or disease that resulted in the person
dying), Determine the mechanism of death (the physiological reason that the person died),
classify the manner of the death (whether Natural, Accidental, suicide, Homicide,
Uncertain), Inform the subsequent scene
6. Photographer
7. Technician
8. Lab experts

4. Crime Scene Investigation- The Seven Important Stages

The Eight Stages of Scene of Crime Examination are:-
1. Securing the crime scene
2. Scanning the scene
3. Sketching the scene
4. Searching for evidence
5. Documentation of crime scene
6. Securing, Collecting & Packaging of evidence
7. Chain of Custody
8. Crime Scene Reconstruction

Now let us understand these stages in detail:-

4.1Securing the Crime Scene

The scene of crime should be secure in manner to isolate the crime scene from the people
who can disturb the potential evidence. It may disturb the investigation.

a) When a crime is called in, the first officer at the scene should:

 Protect the scene to safeguard the damage of evidence

 Anyone not involved in the investigation must be kept out
 No one must use the toilet, towels, phone, lights etc.

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MODULE No. 1: Crime Scene Management & Investigation
 b) On arrival at scene of crime the first priority for an investigation officer is to
provide medical assistance to individuals & arresting the perpetrators.
c) Ropes or barriers and protectors will preserve illegal access to the area.
d) Each person who come in the scene of crime has the potential to damage physical
evidence.
e) Ask the following questions:
i. When did the crime occur?
ii. Who called in the crime?
iii. Who is the victim?
iv. Can the perpetrator be identified?
v. What did you see happen?
vi. Where were you when you observed the crime scene?

4.2 Scanning the Scene

The crime scene should be scanned cautiously in order to find out the hidden details of the
scene. A walk through must be performed by the crime scene investigator, the officer, and
occasionally the lead detective in order to psychologically prepare a reconstruction theory.
The crime scene investigator must note the following things:

a) Any temporary or unconfirmed evidence which can change over time must be
noted.
b) The environmental conditional and weather conditions must be recorded properly.
c) Point of entry, exit and path of travel within the crime scene.
d) Record the initial records like who, what, where, when and how.
e) Recognize special requirements contained by the crime scene for persons,
protections, or apparatus and inform senior officers or other agencies.

4.3 Sketching the Scene

The concluding phase in writing down the scene is creation a crime scene sketch. The
weakness of pictures is that they are 2-D illustrations of 3-D objects. As a outcome, most
pictures can misrepresent the three-dimensional relations of the snapped items showing
items to look nearer together or further at a distance than they actually are. A sketch is
usually made of the scene as if one is looking straight down (overhead sketch) or straight
ahead (elevation sketch) at a crime scene.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

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 A rough sketch at the scene is generally prepared initially on graph paper by pencil. A final
sketch can be made later using inks, paper, and ruler, or a computer. The original rough
sketch must be reserved and well-maintained in case it is needed at a later date. Once the
scene has been systematically documented then the evidence gathering can started.

4.4 Searching for Evidence

Before searching for evidence it is very essential to know what could be the sources of
evidence. The following sources may provide potential evidence which may lead to
investigation:-
a) Body
b) Primary and/or secondary crime scene
c) Suspect(s)

The Primary crime scene is defined as the place where the crime took place whereas a
Secondary crime scene is a location other than the primary crime scene, but that is in some
way related to the crime, where evidence is found.

There are various search patterns to look for evidences. The examining array choose at a
scene of crime depended on the dimensions & location of the scene & also on the number
of gatherers contributing in the search.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 1: Crime Scene Management & Investigation
 Typical examples of crime scene search patterns are:

1. Grid
2. Line or strip method
3. Quadrant or Zone
4. Wheel or ray method
5. Spiral

Now let us understand all these methods in detail:-

Grid Method- It is basically a double line search method. It is a very operational method
but time consuming.

Line or Strip Method— this method is best in large and outdoor crime scenes.

Quadrant or Zone Method— this method is most effective in houses or buildings. Groups
are allocated in small zones for examining.
Wheel or Ray Method—Wheel or ray method is best on small and circular crime scenes.

Spiral Method— it can go internal or external. It is best used when there is no physical
barricades are present.

The given pictures may help in understanding crime search patterns more effectively

SPIRAL GRID LINEAR

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 4.5 Documentation of Crime Scene
Timely recording of an offence scene is very essential for the investigation and any
subsequent trials the reason being that a scene of crime remains untouched is very limited.
The following three methods are used for the crime scene recording:-

1. Photography & Videography

2. Sketches
3. Notes

1. Photography & Videography

An unaltered crime scene is very important. In case any object is moved/removed/replaced

it should be noted properly. In no situations it should be reintroduced. Remember following
points while photographing the crime scene:

1. Crime scene photos should include the immediate scene.

2. The photographs must be taken from all relevant angles and adjacent areas.
3. The close-ups of victim’s relative position in the scene and any injuries must be
photographed.
4. Photograph any possible weapons
5. Photograph the area under the body
6. Photo record all evidence as it is found and if size is significant a point of reference
should be included in the picture.
7. Use advanced technology to record crime scene such as digital photos which allow
near three-dimensional panoramic views of the scene of crime.
8. Photos of scene and surroundings should be taken. The mid-range to close-up
photos with various angles of each piece of evidence should be taken.

Videotaping scene of crime is rising in popularity. While videotaping the crime scene the
investigator must narrate as he/she records the scene. Videography allows for description
(non-subjective) and diverse perceptions.

2. Sketches—the sketch must include date, time, scale, reference points, distance
measurements, names of investigators, victims, suspects, a legend (key) etc.

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 3. Notes

The maintenance of notes is a persistent work when handling a scene of crime and the
notes must include

a) Detailed written descriptions of Crime Scene with locations of potential evidence

(including time of discover of evidence and who find it, who packed and marked it,
disposition of item after being collected etc.).
b) The notes must be detailed enough to refresh one’s memory even after months or
years after processing.
c) Date, time, explanation of the location, weather & environmental conditions,
description of the crime, location of the evidence relative to other key points, the
names of all persons involved, alterations that have happened, and other important
information.

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 4.6 Securing, Collecting & Packaging of Evidence
One team member must be assigned to look for the evidence collection. It should be done
to ensure that the evidence is collected, packaged marked, sealed, and preserved in a
consistent manner, maintaining the chain of custody. Evidence can be substantial to
microscopic.

a) Every article should be placed in a isolated container, sealed, and labeled.

b) The most delicate evidence is gathered and packed first.
c) Various kinds of evidence need particular or special assembly and packing
methods.
d) The body is the property of the coroner or medical examiner; gathering of evidence
on the body is complete by that division.
e) It can only be identified in crime lab ex. traces of blood on clothing, hair and fibers
from vacuum sweeps.
f) It is occasionally essential to seize clothing from victim and perpetrator.

g) Critical regions must be vacuumed; sweepings from diverse areas should be kept
separate.

h) Finger nail scratching must also be taken from suspects and victims

i) All evidence needs to be properly packaged, sealed and labeled.

j) The evidence record must comprise all relevant information consisting:

• Case No.
• Item inventory No.
• Description of the evidence
• Name of suspect
• Name of victim
• Date & time of recovery
• Signature of person recovering the evidence
• Signature of any witnesses present

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 k) Most items should be packaged in a primary container and then placed inside a
secondary one.
l) Pill bottles, vials, manila envelopes, and plastic bags are good for most evidence.
m) Trace evidence may be placed on a piece of paper which is then folded in a
particular way called a “druggist’s fold.”
n) These are then placed inside other containers such as paper bags, plastic bags,
canisters, packets, or envelopes, depending on the type and size of the evidence.
o) Evidence is placed in a paper bindle. The size of the bindle depends depends on the
size of the evidence.
p) Entire object should be sent to the lab.
q) Each different item must be placed in separate containers. Packaging evidence
separately prevents cross contamination.
r) Unbreakable plastic pill bottles excellent containers for hair, fiber, glass evidence
s) Small amounts of trace evidence can be conveniently packaged in a carefully folded
paper called druggist fold. Folding one end of the paper over 1/3, then folding the
other end (1/3) over that, & the repeating the process from the two sides. After the
paper is folded, the outside 2 edges are tucked into each other to produce a closed
container.

4.7 Chain of custody

Maintenance of Chain of Custody is very essential. The chain of custody may be defined as
the documented and unbroken transfer of evidence. There must be a written record of all
people who have had possession of an item of evidence, beginning at the time of collection.

1. Every person who handles the evidence must be accounted for.

2. The evidence container must be marked for identification.
3. If evidence is turned over to another person, the transfer must be recorded.
4. An evidence log and a chain of custody document must be attached to every
evidence container.
5. All items must be carefully packaged & marked upon their retrieval at the scene.
6. Record to show collector’s initials, location of evidence, & date of collection.
7. Seal the evidence & the collector’s signature is written across the sealed edge.
8. When the package is reopened at the lab it is opened at a location other than the
sealed edge.
9. Every time opened: new seal, new signature, and place in new evidence bag.

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 4.8 Crime Scene Reconstruction
Crime scene reconstruction is a method used to support a likely sequence of events at a
crime scene by observing & evaluating physical evidence & statements made by those
involved. Reconstruction of crime scene is a team effort which involves putting together
many different pieces of a puzzle.

The collection & documentation of physical evidence is the foundation of a reconstruction.

The investigator captures the nature of the scene on an initial walk through. Using physical
evidence the investigator can hypothesize about what occurred, where it occurred & when
it occurred. Reconstruction of crime scene involves forming a hypothesis of the sequence
of events from before the crime was committed through its commission.

5. Summary
1. A crime is defined as an act or the commission of an act that is forbidden or the
omission of a duty that is commanded by a public law and that makes the offender
liable to punishment by that law.

2. Outdoor crime scenes are the most difficult to investigate due to the exposure of
scene to rain, wind, heat, animal activity as they contaminates the crime scene and
leads to the destruction of evidence.

3. A Successful Crime Scene Investigation utilizes a step by step process in the

discovery, preservation and collection of Physical Evidence..

4. The Locard’s Exchange Principle states that when a person comes into contact with
an object or another person, a cross transfer of physical evidence can occur. The
exchanged materials indicate the two objects were in contact.

5. A crime scene team includes Team members, First police officer on the scene to
protect the scene, Medics, Investigators, Medical examiner, Photographer,
Technician and Lab experts.

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 6. A Medical Examiner is responsible for Identify the deceased, Establish the time and
date of death, determine a medical cause of death, determine the mechanism of
death, Classify the manner of death and notify the next of kin.

7. The crime scene investigator must note any transient or conditional evidence that
could change over time must be noted, the environmental conditional and weather
conditions must be recorded properly, point of entry, exit and path of travel within
the crime scene, Record the initial observations such as who, what, where, when
and how.

8. A rough sketch at the scene is usually made first on graph paper in pencil. A final
sketch can be made later using inks, paper, and ruler, or a computer.

9. Grid, Line or strip method, Quadrant or Zone, Wheel or ray method and Spiral are
the typical examples of crime scene search patterns for evidence collection.

10. The search pattern selected at a crime scene depends on the size & locale of the
scene & also on the number of collectors participating in the search.

11. Date, time, description of the location, weather & environmental conditions,
description of the crime, location of the evidence relative to other key points, the
names of all people involved, modifications that have occurred, and other relevant
information.

12. The chain of custody may be defined as the documented and unbroken transfer of
evidence.

13. Crime scene reconstruction is a method used to support a likely sequence of events
at a crime scene by observing & evaluating physical evidence & statements made
by those involved.

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MODULE No. 1: Crime Scene Management & Investigation
 SUBJECT FORENSIC SCIENCE

Paper No. and Title PAPER No.7: Criminalistics and Forensic Physics

Module No. and Title MODULE No.2: Protection, Securing and Isolating the
Crime Scene
Module Tag FSC_P7_M2

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.2 : Protection, Securing and Isolating the
Crime Scene
 TABLE OF CONTENTS

1. Learning Outcomes
2. Significance of Crime Scene
3. Protecting, Securing and Isolating the Crime Scene
4. Summary

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.2 : Protection, Securing and Isolating the
Crime Scene
 1. Learning Outcomes

After studying this module, you shall be able to learn about the-

 Significance of crime scene and

 How to Protect, Secure and Isolate the Crime Scene

2. Significance of Crime Scene

The most significant characteristic of evidence collection and their preservation is securing
the crime scene. This is to preserve the pertinent evidence clean till it can be documented
and collected. The successful examination of a case can hinge on the state of the physical
evidence at the time it is collected.

The protection of the crime scene starts when the first police officer enters and ends with
its release from the police custody. Crime scene itself is of high value evidence when
processed properly. Any police officer can be a first responding officer to a crime scene. A
thorough training for all personnel of police departments should be done on the process of
properly isolation and protection the crime scene. The first responding officer should
approach the scene slowly and methodically.

Protection of the crime scene also includes protection of the crime scene investigators. A
person, he may be either a civilian or a police crime scene investigator, would by no means
be left alone during handing of the scene. It is very true if the suspect has not been
detained, there will be many stories of suspects hiding at or near their area of crime. Hence,
there should always be at least two persons working the scene and should carry a radio and
a firearm.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

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 In the case of a suspected criminal activity the role of the physical evidence is crucial that
helps in the overall investigation and resolution of crime. The potential value of the
physical evidences is realized based on the actions taken during the investigation of crime
scene. Proper documentation and preservation of the physical evidences recovered from the
scene of crime will have greater value due to the advancements and improvements taking
place in the field of technology.

The most important part is the preservation and recognition of the physical evidences
obtained from the scene of crime and which readily helps in yielding trustworthy
information pertaining to the investigation. Also, an important factor governing the
scientific value of the evidence is that the crime scene investigators follow an objective,
thorough, and thoughtful approach.

The crime scene investigators should always approach a crime scene with a notion that it
will be their last chance of preserving and recovering the potential evidences. Also during
their objective assessment, the investigators should take into consideration statements
obtained from witnesses and suspects and other information pertaining to the case. The
physical clues and the inquiries related with the case that were initially thought to be inapt
may help in solving the case wherein the investigations may change a number of times.

It is recognized that all crime scenes are unique. The crime scene investigator giving the
judgement with help from other responders, for example the prosecutor should be given in
regard with the findings related to the case. It is impossible to propose a single, step-by-
step procedure to approach every type of situation. Therefore, while investigating a crime
scene and also during preservation of evidence fundamental principles needs to be
followed.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.2 : Protection, Securing and Isolating the
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 3. Protecting, securing and isolating the Crime Scene

Most of the times, the entry of additional personnel can create problems in securing the
scene. Only those persons accountable for the immediate investigation of the crime, the
securing of the crime scene, and the handling of the crime scene should be present.

The investigating officer cannot always reach the crime scene immediately after the
occurrence. The first official who reaches the scene, therefore, should be careful to
preserve the evidence:-

1. First responding officer should ensure the-

 Safety of Crime Scene

 Preserve evidence
o Protect area
o Limit exchange
o Request team
 Separating the Witnesses

2. All items must be documented & photographed.

3. Scan the scene to determine what photos are needed

– May determine primary and secondary crime scene

4. The lead investigator evaluates the scene & determines the boundaries. They do an
initial walk through & develop a strategy.

5. Do an initial walk-through – this should be done along with the initial responding
officer who can add any information they may have obtained prior to your arrival.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

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 6. Develop a strategy for systematically:

a) Examining/investigating the crime scene

b) Documenting the crime scene investigation

7. Interview initial responding officers (RO’s) – this would include:

a) Law enforcement officers responding to the initial call

b) Backup officers who responded to the scene

8. First priority is to provide medical assistance to individuals. The injured body or

bodies must be checked first for any signs of life. In case there are only few chances
of life, medical help should be called in immediately to transport injured to the
nearest hospital. In this process care must be taken to disturb the scene to minimum
extent.

9. Establish the scope and range of the scene –this includes:

a) Physical boundaries of the scene

b) Secondary scenes such as associated vehicles or relevant sites outside the
physical boundaries of the scene

10. Anything from the scene should not be moved. Anything present at the scene
should be recorded by sketches and photographs.

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 11. Every person who enters the crime scene has the potential to destroy physical
evidence.

12. Identify all other persons who have or have had access to the scene – this would
include:

a) Other law enforcement officers

b) Coroner’s personnel
c) Any public safety personnel (fire, ambulance, etc.)
d) Any civilians present (residents, neighbors, newspersons etc.)

13. Non-essential persons should never be permitted to enter into a secured crime scene
until they have important role in the crime scene investigation. One way to
discourage needless people from entering the crime scene is to make only one
entrance/exit into the crime scene. An officer can be placed here with a notebook to
take the names of all of the people entering the crime scene. The officer should then
notify them that by entering the crime scene they may create a difficulty by forming
probable contamination, and the reason behind the officer taking their names is in
case the crime scene investigators require to collect fingerprints, shoes, fibers,
blood, saliva, dragged head hair, and/or pulled pubic hair from all those entering the
crime scene. This will sometimes discourage non-essential personnel from entering
the crime scene. The officer can also stop unwanted visitors from entering the
restricted areas. If extraneous people do have to enter the scene, then make sure that
they are escorted by someone who is working the scene. This is to make sure that
they will not inadvertently destroy any valuable evidence or leave any worthless
evidence.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.2 : Protection, Securing and Isolating the
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 14. All unauthorized person including friends and relatives of the victim, media,
onlookers should be eliminated from the scene first.

15. Ropes or barricades and guards will prevent unauthorized access to the area.

16. The scene of crime should be barricaded so that the scene remains unaltered. The
larger area must be barricade instead of smaller one so that no clues/evidence is left
out.

17. Personnel of home guard/or similar organizations should be employed to protect the
scene, if required.

18. The police officer should not leave the crime scene unguarded.
19. Eating, drinking, or smoking should never be allowed at a crime scene. Not only
can this wreck a crime scene but it can also be a health hazard.
20. Physically secure the scenes with police line tape or by other means and have law
enforcement officers available to enforce the scene perimeter.

21. Establish the perpetrator’s path of entry and exit – this includes identifying any
obvious pieces of evidence that comes to the attention of the crime scene
investigator.

22. If the culprit is found red handed or positively he should be immediately arrested.

23. Only the officer in charge of the case should determine when, why and who is to
enter the scene.

24. Assistance of forensic experts, medico legal experts, police officers, photographers
should be requisitioned at the earliest, if required.

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 25. The details of informant with his address, the time when he gave information and
the alleged time of occurrence should be recorded.

26. Ask the following questions:

i. When did the crime occur?

ii. Who called in the crime?
iii. Who is the victim?
iv. Can the perpetrator be identified?
v. What did you see happen?
vi. Where were you when you observed the crime scene?

27. It should be make sure that suspect and witness do not discuss the case with each
other.

28. The case should not be discussed with the suspects, the complainants, the victims,
the witnesses, the onlookers or the pressmen.

29. The behavior of the persons around should be observed.

30. The officer should not introduce any material like foot, footwear, cigarette ash/ends,
and fingerprints at the crime scene.

31. Till the examination is finalized, the doors, windows, stair cases, lighting, routes of
ingress and egress should be preserved in original condition.

32. The officer should record his own time of arrival, note and record the weather
conditions.

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 33. Some things the officer should note include:

 The condition of the doors, windows, and lighting (both natural and manmade);
 If there are any signs of activity;
 If in any cases alteration of position of object is made which is permitted in
emergencies then record the change if made.
 How EMS or fire personnel have altered the scene;
 Anything essential about the suspect (description, statements, physical
condition, mental condition, intoxication, etc.);
 Anything essential about the victim;
 The officer should make mental or written notes about the condition of the
crime scene as it was upon the officer's arrival and after the scene has been
stabilized.
 The officer should keep notes on the significant times involved in responding to
the crime scene (time dispatched to scene, time left for scene, time arrived at
scene, time left scene, etc.).
 If any odor of alcohol, tobacco, explosives, and perfumes are observed, it
should be noted.

34. Investigators and other necessary personnel should be contacted and dispatched to
the scene; however, under no circumstances should the telephone at the scene be
used.

35. The officer or any other person should not use the utilities of the scene such as
lavatory, washbasin, bathroom etc.

36. The scene should not be cleaned no matter how messy it is.

37. Try To Prevent Collusion.

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 38. Securing the scene – this can be difficult on occasion, especially in the case of high
profile cases where news persons, and onlookers may become unruly or persistent.
Also, high profile cases attract high ranking law enforcement persons who,
technically, have nothing to do with the case and have no business being on the
scene.

4. Summary

1. Protecting the crime scene is the most important aspect of evidence collection and
preservation.
2. Any police officer can be a first responding officer to a crime scene so an intensive
training for all personnel of police departments should be done on how to properly
protect, isolate and secure the crime scene.
3. First responding officer should ensure the Safety of Crime Scene, preservence of
evidence, Protection of area, Limit exchange and separating the Witnesses.
4. All items must be documented & photographed.
5. Provide medical assistance to individuals on priority. In this process care must be
taken to disturb the scene to minimum extent.
6. Anything from the scene should not be moved.
7. Every person who enters the crime scene has the potential to destroy physical
evidence.
8. All unauthorized person including friends and relatives of the victim, media,
onlookers should be eliminated from the scene first.
9. Ropes or barricades and guards will prevent unauthorized access to the area. The
scene of crime should be barricaded so that the scene remains unaltered.
10. The larger area must be barricade instead of smaller one so that no clues/evidence is
left out.
11. Personnel of home guard/or similar organizations should be employed to protect the
scene, if required.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.2 : Protection, Securing and Isolating the
Crime Scene
 12. The police officer should not leave the crime scene unguarded.
13. Establish the perpetrator’s path of entry and exit – this includes identifying any
obvious pieces of evidence that comes to the attention of the crime scene
investigator.
14. If the culprit is found red handed or positively he should be immediately arrested.
15. Assistance of forensic experts, medico legal experts, police officers, photographers
should be requisitioned at the earliest, if required.
16. The details of informant with his address, the time when he gave information and
the alleged time of occurrence should be recorded.
17. It should be make sure that suspect and witness do not discuss the case with each
other.
18. The case should not be discussed with the suspects, the complainants, the victims,
the witnesses, the onlookers or the media personnel’s.
19. The officer should not introduce any material like foot, footwear, cigarette ash/ends,
and fingerprints at the crime scene.
20. The officer should record his own time of arrival, note and record the weather
conditions.
21. Investigators and other necessary personnel should be contacted and dispatched to
the scene.
22. The scene should not be cleaned no matter how messy it is.
23. Try To Prevent Collusion

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.2 : Protection, Securing and Isolating the
Crime Scene
 SUBJECT FORENSIC SCIENCE
Paper No. and Title PAPER No.7: Criminalistics and Forensic Physics

Module No. and Title MODULE No.3: Documentation of Crime Scene

Module Tag FSC_P7_M3

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 3: Documentation of Crime Scene
 TABLE OF CONTENTS

1. Learning Outcomes
2. Documenting the crime scene
3. Documenting the scene using Videotape recording
4. Documenting the scene using Photographs
5. Photographing of specific evidence
6. Advantages and Disadvantages of documenting the crime scene using
photographs
7. Photographic Equipments
8. Admissibility of photographs in the Court of Law.
9. Videotape Documentation Vs Photograph Documentation.
10. Summary

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 3: Documentation of Crime Scene
 1. Learning Outcomes

After studying this module, you shall be able to learn about the

 Significance of documenting the crime scene,

 Documenting the scene using Videotape recording and photographs,
 Points to remember while photographing some specific evidence,
 Advantages and disadvantages of documenting the crime scene using photographs,
 Common equipment used to photograph the crime scene,
 Admissibility of photographic evidence in the Court of Law

2. Documenting the Crime Scene

To build a solid case in court it is essential to collect all of the evidence at the scene and to
document it properly. If the evidence is located properly and the investigator failed to
document it properly the evidence may end up being worthless in court.

Documentation of crime scene is the very vital and time-taking task. The Scene of Crime
can be documented in many ways including using videotape, Photography etc. the crime
scene is documented in order to

1. To have information about the original scene and linked places.

2. To have a record of preliminary form of physical evidence.

3. It will give investigators permanent pictorial record of the Scene for after use.

4. Documentation is also used in court trials and hearings.

The documentation

 Displays the evidence in the relation of the scene of crime.

 Allows restoration of the corpus delecti.

 Assistances for creating and maintaining the chain of custody.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 3: Documentation of Crime Scene
 At each crime scene there are 2 general queries for the Crime Scene Officer:

How will you discover the evidence and how will appropriately document it once it is
found?

While documenting a crime scene the crime scene officer must record the information like

• Who?
• What?
• Where?
• When?
• How?
• Why?

The documentation of Crime Scene can be covered in three procedures as stated under.
Ideally all three methods must be used

1) Video Recording & Photography,

2) Sketches, &
3) Notes

Here, only, the significance of documentation of crime scene using Video Recording &
photographs is discussed.

Whether a video camera is available or not it is always necessary to take still photographs
in order to document the crime scene. If a video camera is accessible, then pictures will be
the second step in recording scene of crime and if a video camera is not available, then still
photography would be the first step.

3. Documenting the Scene using Videotape Recording

It is a very common observing medium in representative the assembly of the crime scene
and how the evidence associates to the crime. Prior to taping, the camera quality must be
cleared of all personnel. Any individuals in the area must be cautioned that taping is for

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 3: Documentation of Crime Scene
 initiate in order to avoid any kind of unwanted noise. Once the video camera started
recording, it must not be halted till the taping is finished.

While videotaping the crime scene the following points must always be keep in mind:

1. The video camera should have a fully charged battery.

2. The fundamental for good recording is slow camera movement.
3. The taping should start with an overall outline of the scene and surrounding area.
4. The video camera would have date and time videotape display functions.
5. The condition of the scene should remain unaltered.
6. The taping should remain all over the crime scene by wide angle, close up, and even
macro (extreme close up) shots to determine the outline of the evidence and its
relevance to the crime scene.
7. The markers placed by the investigators and any lights turned on during the walk
through can be noted on the audio portion of the tape.
8. Keep around 15 seconds of blank tape (after the tapping is complete) to prevent the
crime scene tape from running into anything else previously recorded on the tape.
9. The tape after then shifted to a good quality master tape.
10. The footage tabs must be detached from the master tape after shifting the crime
scene tape and the master should be stored in a safe place in order to prevent
accidental erasure of the crime scene tape.
11. If required, reproductions can then be prepared from the master tape.

The widespread videotape is being applied in crime scene investigation in recent times.
But, some disadvantages are also there along with advantages of videotaping which are
mentioned below:

Advantages Disadvantages
It provides an “in person” view of the scene A person can never move too slowly when
as well as of the evidence. videotaping, yet it is all too easy to move
the camera fast without realizing it.

That’s why videotaping is not ideal for

viewing detail.

It permits for a continuous narrative of the

crime scene investigator especially during
primary walk-through and subsequent re-
construction of the crime.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 3: Documentation of Crime Scene
 4. Documenting the Scene using Photographs
Photographs and videotape demonstrates the similar kind of things, but photographs from
the crime scene can also be used in direct comparison situations. For example, one-to-one
photographs (also called as real size photos) can be used to match fingerprint/ shoeprints
snapped at the crime scene to known fingerprints/shoeprint from a suspect.

1. When photographing the scene, first, take enough photographs.

2. It is quite usual to take 200-400 photos of a major crime scene.
3. Take only those pictures which are relevant to the case because everything
photographed goes to the defense, so don’t photograph anything inappropriate.
4. Nearly every form of camera with substitutable lenses and a set-up of 35mm or
greater is used in crime scene photography.
5. The lenses of camera must comprise a 28mm wide angle lens, a normal 55mm lens,
and a lens with macro capabilities (1:4 or better with this).
6. The flash component should not be attached one with the camera and should be able
to function at various angles and distances from the camera. This helps in allowing
lighting of certain areas to provide maximum contrast. Place the flash in difficult to
reach areas, and reduce flash wash out which can render the item photographed
invisible.
7. For one-to-one photography a tripod, a level, and a small ruler must also be
accessible. It can be of assistance to the examination to have a Polaroid camera
handy for instant photographs.
8. The photography of the crime scene must start with wide angle photos of the crime
scene and surrounding areas.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 3: Documentation of Crime Scene
 9. The pictures of complete scene should show the layout of the crime scene and the
overall spatial relationships of the various evidences to each other.
10. In indoors photography the altogether 4 corners of a room should be photographed
to show its overall arrangement.
11. One set of photos should be of medium range to display the associations of
individual portions of evidence to other pieces of evidence or structures in the crime
scene.
12. The significant parts of evidence must be photographed by taking close up photos.
13. What the investigator is capturing or desires to demonstrate in each photograph must
be noted. This prevents the investigator from taking the photo back at a later date
and trying to sort out what he was trying to achieve with the photograph.
14. The sequence must be sustained while photographing the same areas.
15. The photographer should take a methodical and logical sequence of photographs.
16. The pictures of victims and of individuals in the mob nearby the scene must be
photographed.
17. Take photographs that cover all viewpoints of the scene (which shows an inclusive
vision, a medium vision, and close-ups).

18. Close-up photos must comprise a scale that will relate with the article number used
on the Evidence Custody Sheet.

19. The photographer must take pictures of evidence as it is collected and should keep a
log of his photos.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 3: Documentation of Crime Scene
 20. The photographer must create a photo log which includes:-

a. Date and time

b. Camera settings
c. Film roll number and exposure number or file name and exposure number
d. Type of shot
e. Distance to the subject
f. Brief description

21. After photographing all of the evidences, collect the evidence and prepare the
Evidence Custody Sheet (a report which documents all of evidence).

22. Evidence Custody Sheet comprises:

– Each piece of evidence along with its item number. The item number for each piece
of evidence must correspond with the number found on the photograph of the item
and the number entered on any evidence collection bags, etc.

– what was done with it,

– where it was found, etc.

23. The original digital images must be archived and copies should use to work.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 3: Documentation of Crime Scene
 5. Photographing of Specific Evidence

Types of Evidence
Fingerprints Impressions Bloodstains Death Scene including
(Footprints and tire a corpse
tracks)

1).Before lifting 1).Take an orientation 1).Use color film 1).Take at least 200-
fingerprints on major photograph to show 500 shots from every
cases where in the scene the 2).Orientation possible angle of view.
impression is located photographs to
2).If the latent may be show locations of 2).Take photos to show
destroyed when lifting 2).Take a close-up for bloodstain evidence body’s location &
detail at the scene position relative to the
3).To bring out detail in whole crime scene
a latent 3).Close-up
photographs to 3).Take close-up
show detail photos of injuries &
weapons lying near the
a). Use a scale on body
the same plane as
the bloodstain 4).After the body is
removed, photograph
b). Keep the film the surface underneath.
parallel to the plane
of the bloodstain

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 3: Documentation of Crime Scene
 6. Advantages and Disadvantages of documenting crime scene using
Photographs

Photographs
Advantages Disadvantages
They can be taken immediately They are not selective
They accurately represent the crime scene They do not show actual distances
and evidence
They create interest and increase attention to They may be distorted and damaged by
testimony mechanical errors in shooting or processing

7. Photographic Equipments
There are many types of photographic equipment available in the market. Some of the
common photographic equipments are mentioned below:

 Digital camera
 Instant print camera
 Fingerprint camera
 Video equipment

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 3: Documentation of Crime Scene
 There are many kinds of photography carry out for several reasons. Here, few details about
the investigative photography and Laboratory Photography are given in table:-

Types of Investigative Photography Types of Laboratory Photography

Surveillance Photography Microphotography- It takes pictures through a microscope
Aerial Photography Macrophotography- It enlarges a subject before photography
Night Photography Laser-beam Photography- It reveals evidence indiscernible to
the naked eye

Laboratory Photography Ultraviolet-light Photography- uses the low end of the color
spectrum to make visible impressions of bruises and injuries
long after their actual occurrence
Mug Shots
Lineup Photographs

8. Admissibility of Photographic evidence in the Court of Law

The following are the three major points of qualification of a photograph in court:-

1. Object pictured must be material or relevant to the point in issue.

2. The photograph must not appeal to the emotions or tend to prejudice the court or
jury.
3. The photograph must be free from distortion and not misrepresent the scene or the
object it purports to reproduce.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 3: Documentation of Crime Scene
 9. Videotape Documentation Vs. Photograph Documentation

Videotape provides a viewpoint on the crime scene layout which cannot be as easily
perceived in photographs.

If videotaping is carrying out in a residence, the camera can show how the significant
rooms are laid out in relation to each other and how they can be accessed. This is
sometimes lost in photographs and sketches.

Actual size photographs from the crime scene can be used in direct comparison situations.
For example, to compare fingerprint photographed at the crime scene to known fingerprints
from a suspect. This lacks in videotapes.

10. Summary

1. Documentation of crime scene is done to record the original scene and related areas,
the initial appearance of physical evidence, to provide investigators and others with
this permanent visual record of the scene for later use and for use in court trials and
hearings.

2. The documentation shows the evidence in the context of the crime scene, allows
reconstruction of the corpus delecti and helps to create and maintain the chain of
custody

3. Photographs and videotape demonstrates the same type of things, but photographs
can also be used in direct comparison situations. For example to compare the
questioned and known fingerprint/ shoeprints.

4. Take photos to show body’s location & position relative to the whole crime scene,
take close-up photos of injuries & weapons lying near the body and after the body is
removed, photograph the surface underneath.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 3: Documentation of Crime Scene
 5. To qualify photographic evidence in court the object pictured must be material or
relevant to the point in issue, the photograph must not appeal to the emotions or
tend to prejudice the court or jury and the photograph must be free from distortion
and not misrepresent the scene or the object it purports to reproduce.

6. Videotaping in a residence must show how the significant rooms are laid out in
relation to each other and how they can be accessed.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 3: Documentation of Crime Scene
 SUBJECT FORENSIC SCIENCE

Paper No. and Title PAPER No.7: Criminalistics and Forensic Physics

Module No. and Title MODULE No.4: Importance of Field Notes & Sketching at
the Crime Scene
Module Tag FSC_P7_M4

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 4 : Importance of Field Notes &
Sketching at the Crime Scene
 TABLE OF CONTENTS

1. Learning Outcomes
2. Field Notes
3. Crime Scene Sketch
4. Summary

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 4 : Importance of Field Notes &
Sketching at the Crime Scene
 1. Learning Outcomes
After studying this module, you shall be able to learn-

 About field notes

 Crime scene sketch and their significance

2. Field Notes

The documentation of the case starts as soon as an officer gets a call that a crime has
occurred till the moment of case closing. It is a most important as well as time consuming
process. Documentation of crime scene is done to record and preserve the location &
condition of evidence. The respective location of evidences with each other is also
recorded. Usually four types of documentation methods are adopted by investigating
officer. These are:-

1) Reports and note-taking or field notes (sometimes audio)

2) Photographs
3) Videography
4) Crime scene sketching and mapping

Now let us understand the significance of field notes in detail.

Field notes are short written record of events, places, times, suspects, witnesses and other
relevant information. This information is used to prepare report. Some elements should be
included in all reports. Regardless of the offense, the effective and complete notes are
important. On arrival at the crime scene, an effort should be made to gain as much as
information as possible. The reason behind is the information that seem unnecessary at first
may later proves to be highly valuable to the investigator.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 4 : Importance of Field Notes &
Sketching at the Crime Scene
 Field Notes must be prepared which shows what actually is demonstrating in photographs.
It helps in preventing the investigator from getting the picture back at a later date and
trying to figure out what he or she was trying to accomplish with the photo.

Now let us discuss the importance of Fields Notes:-

1) Detailed notes can make or break a conviction

2) Reliability:-Field notes are more reliable than memory of investigating officer. Later in
any stage of investigation the officer may forget or skip some potential detail. It only takes
a short period of time for some important details to slide away from the memory. To
prevent the loss of potential information is to depend on field notes prepared by the
investigating officer.

3) Primary Source of Information: - Primary information source are Field Notes for the
Offense Report because the first-responding officer is usually the person who writes any
incident report which is required by the situation.

4) Representative: - Field notes are significant as they present the detail which makes the
content of the event report.

5) An investigating officer may need to contact the victims or witness of the crime
regarding information that was overlooked or questions that were not asked in the initial
contact. Once in a while, victims and witnesses get annoyed and even angry when they are
re-contacted by an officer who obviously did not take good field notes when he/she talked
to them earlier and therefore cannot complete the incident report without additional
information. Detailed Field Notes May Reduce the Need to Re-contact the Parties involved
(victims and witnesses).

6) Field Notes can be used to defend the integrity of the Incident/Offense Report.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 4 : Importance of Field Notes &
Sketching at the Crime Scene
 7) Refreshing Memory:-Finally, it is not uncommon for officers/investigators to testify in
court several months or years later regarding a particular investigation. Comprehensive
field notes help refresh the investigator‟s memory as well as strengthen his or her court
testimony.

The field notes can be used during courtroom testimony to refresh recollection of the
events. Field notes are more trustworthy than an individual‟s memory as it can be used as a
source of particular facts and details that else may be forgotten.

8) Investigative notes are a permanent record of the evidences of a case to be used for
further investigation or in writing reports.

9) There are numerous other questions which must be asked called primary questions.
These include: what, when where, who, how, and why. Although no single set of questions
can meet the needs for investigating all types of crime, there are six primary questions
which have long be recognized in the field for being useful.

10) While preparing field notes

a) Don‟t include words such as: a, and, and the

b) Use standard abbreviations such as mph, DWI, and Ave
c) Describe everything; the location, weather, type of crime, all physical evidence, etc.
d) Make notes in ink, in a bound notebook, with pages numbered sequentially.
e) Do not erase errors; cross them out with pen.
f) Make notations in chronological order.
g) Evidence is documented by describing: Type and condition of evidence, Time of
discovery, Name of discoverer, Placement, Collection, Packaging & Labeling of
Evidence Recovered.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 4 : Importance of Field Notes &
Sketching at the Crime Scene
 3. Crime Scene Sketch

Preparing a crime scene sketch is the final phase in crime scene documentation. A crime
scene sketch is a permanent record of the size and distance relationship of the crime scene
and the physical evidence within it. Sketching of crime scene provides spatial relationship
between objects. While other methods do not allow the viewer to measure easily the
distances and dimensions, the crime scene sketch solves this purpose by elucidating the
information contained in the photographs and video documentation.

A sketch is the most simplistic manner in which to present crime scene layout and
measurements. In crime scene sketching the position of camera and the photographer may
also be noted.

Photographs provides a 2-dimensional representations of three-dimensional objects which

distort the spatial relationships of the photographed objects causing items to appear closer
together or farther apart than they actually are.

If spatial relationships of the evidence are important or if something needs to have

proportional measurements included in it for calculations (such as bullet trajectory angles,
accident reconstructions, etc.) then a sketch must be made of the crime scene.

Two types of sketches are produced with regards to crime scene documentation:

1) Rough Sketches:-Rough sketches are prepared during the crime scene

assessment/preliminary scene evaluation phase to assist with development of a
strategic plan for processing. The sketch is not done to scale, can be drawn with any
implement (crayon, chalk, pencil, pen, etc.), and is very rough artistically. As work
progresses at the crime scene, the sketch will include not only the crude crime scene
layout, but also will be used to record measurements of items and structures, and
distances between items.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 4 : Importance of Field Notes &
Sketching at the Crime Scene
 2) Final/Finished Sketches: - A final sketch is a finished rendition of the rough sketch.
They are usually prepared for courtroom presentation and often will not show all
measurements and distances originally recorded on the rough sketch. Only
significant items and structures are typically present within a final sketch. A final
sketch is produced in either ink or on a computer, in a manner that is not able to be
modified (i.e., not in pencil!). The sketch should be clutter-free and should
accurately depict all pertinent items of evidence, typically through the use of an
accompanying legend. A legend is a note of explanation, outside of the sketch area,
which relates to a specific item, symbol, or information contained within the
graphical representation of a sketch.

A rough sketch at the scene is usually made first on graph paper in pencil with so many
squares representing so many square feet or inches. Using a tape measure or other
measuring devices, measurements are taken at crime scene of the distances between objects
and/or structures at the crime scene. These measurements are proportionally reduced on the
rough sketch and the objects are drawn in. Two measurements taken at right angles to each
other or from two reference points will usually suffice in placing the objects where they
belong in a sketch. Double measurements should also be taken to make sure they are
correct. This is especially true where calculations will later be used. A final sketch should
be made later using inks, paper, and ruler, or a computer. The original rough sketch should
be reserved and well-kept-up in case it is required at a later date. The scene should be
carefully documented then the evidence collection can initiate.

Crime scene sketch has its own significance:-

1. It accurately depicts the physical evidences.

2. It connects to the sequence of events at the scene.
3. It establishes the precise location and relationship of objects and evidence at the
scene.
4. It helps to create a mental picture of the scene for those not present.
5. It is a long-lasting record of the scene.
6. It is acceptable in court.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 4 : Importance of Field Notes &
Sketching at the Crime Scene
 7. It assists in questioning and cross-examining.
8. It assists in preparing the written investigative report.
9. It assists in presenting the case in court. Well-prepared sketches and drawings
help judges, juries, witnesses, and others to visualize the crime scene.
10. Sketch all serious crimes and accident scenes after photographs have been taken
and before anything is moved.
11. Sketch the entire scene, the objects, and the evidence.

A final sketch should include:

1. Title (What does the sketch represent? For example, Sketch of Bank ABC
Robbery).
2. Legend (What do symbols within the sketch mean?).
3. Case Information. (i.e., date, time, place, case number).
4. Initials/Name (person who drew the sketch).
5. Indication of a direction (e.g., North).
6. Scale (e.g.: 1” = 1‟).
7. Measurement table (If measurements are not represented within the confines of the
sketch, an accompanying measurement table should be included to explain the
distances and measurements associated with it.).
8. There should be a system succeeding the scale or measurement table asserting: “All
Measurements are Approximate.” This will ensure that the sketch‟s author does not
get into a credibility argument in court that a measurement is documented as the
listed measurement, but could in fact be greater or lesser due to rounding errors or
other factors.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 4 : Importance of Field Notes &
Sketching at the Crime Scene
 Three different crime scene perspectives can be represented within a sketch. Sometimes
personnel choose to incorporate several perspectives within a sketch (e.g., using both
elevation and overhead sketches to draw an exploded or cross-sectional view of a scene).

1) The Bird’s Eye Or Overhead View: - An overhead or bird‟s eye view is the most
common form of crime scene sketching. It is prepared with the perspective being as though
the author was looking down upon the scene from above. This type shows the floor layout
but cannot represent heights of items or show associated evidence on walls. Direction of
the above view is done through a compass.

2) The Elevation Or Side View: - In order to show such information, a person must
sketch an elevation or side view sketch to show evidence located on a building façade,
interior wall, or any item of which height is an important aspect (e.g., death involving a
hanging).

3) The Three-Dimensional (3d) View:- A 3D crime scene perspective is created with the
aid of computers, and has its primary function as being crime scene activity reconstruction,
to help explain what happened and in what order.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 4 : Importance of Field Notes &
Sketching at the Crime Scene
 4. Summary

1. Documentation of crime scene is done to record and preserve the location &
condition of evidence.
2. The four types of documentation methods are Reports and note-taking,
Photographs, Videography and Crime scene sketching & mapping.
3. To prevent the loss of potential information field notes must be prepared by the
investigating officer.
4. The questions like what, when where, who, how, and why must be asked during
interrogation.
5. Describe the location, weather, type of crime, all physical evidence, etc.
6. Evidence is documented by describing: Type and condition of evidence, Time of
discovery, Name of discoverer, Placement, Collection, Packaging & Labeling of
Evidence Recovered.
7. A crime scene sketch is a permanent record of the size and distance relationship of
the crime scene and the physical evidence within it.
8. Sketching of crime scene provides spatial relationship between objects.
9. Rough Sketches and final sketch are produced in crime scene documentation.
10. The sketch should be clutter-free.
11. The final sketch should accurately depict all pertinent items of evidence with the
help of using „legend‟.
12. A legend is a note of explanation, outside of the sketch area, which relates to a
specific item, symbol, or information contained within the graphical representation
of a sketch.
13. Crime scene sketch accurately portrays the physical facts, relates to the sequence of
events at the scene, and establishes the precise location and relationship of objects
and evidence at the scene.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 4 : Importance of Field Notes &
Sketching at the Crime Scene
 14. Three different crime scene perspectives can be represented within a sketch such as
The Bird‟s Eye or Overhead View, The Elevation or Side View and the Three-
Dimensional (3d) View.
15. An overhead or bird‟s eye view is the most common form of crime scene sketching.
16. Overhead or bird‟s view is prepared with the perspective being as though the author
was looking down upon the scene from above. It shows the floor layout but cannot
represent heights of items or show associated evidence on walls. Directionality of
the overhead view is determined by using a compass.
17. The Elevation or Side View is used to show evidence located on a building façade,
interior wall, or any item of which height is an important aspect (e.g., death
involving a hanging).
18. A 3D crime scene perspective is created with the aid of computers, and has its
primary function as being crime scene activity reconstruction, to help explain what
happened and in what order.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 4 : Importance of Field Notes &
Sketching at the Crime Scene
 SUBJECT FORENSIC SCIENCE
Paper No. and Title PAPER No.7: Criminalistics and Forensic Physics

Module No. and Title MODULE No.5: Types, Significance and Classification of
Physical Evidence
Module Tag FSC_P7_M5

FORENSIC SCIENCE PAPER NO.7 : Criminalistics and Forensic Physics

MODULE NO.5: Types, Significance and Classification of
Physical Evidence
 TABLE OF CONTENTS

1. Learning Outcomes
2. Physical Evidence
2.1 Definition
2.2 Role of Physical Evidence in Forensic Science
2.3 Processing of Physical Evidence
3. Types of physical evidence
3.1 Blood
3.2 Semen
3.3 Saliva
3.4 Documents
3.4.1 Types of document examined
3.4.2 Handwriting examinations
3.4.3 Tools for document examination
3.5 Explosives
3.6 Ballistics Evidence such as Firearms and ammunition
3.5.1 Firearm Evidence Collection
3.5.2 Analysis of firearm Evidence
3.7 Fingerprints
4. Summary

FORENSIC SCIENCE PAPER NO.7 : Criminalistics and Forensic Physics

MODULE NO.5: Types, Significance and Classification of
Physical Evidence
 1. Learning Outcomes
After studying this module, you shall be able to learn about

 What is physical evidence

 Its role in forensic science
 Steps to process physical evidence and
 Different types of physical evidence, in detail, which can be encountered at the crime
scene.

2. Physical Evidence

2.1 Definition
Physical evidence is any material or entity that has an important role in the matter or the criminal
case that finally resulted in the legal proceedings, intended to prove a fact in issue based on its
demonstrable physical characteristics.

2.2 Role of Physical Evidence in Forensic Science

Physical evidence plays an important role in the investigation of a crime. It all depends how
many evidences are recovered and how much potential it has. The evidence left behind plays a
crucial role in reconstruction of events. The physical evidence in itself cannot describe
everything about what exactly happened nevertheless this evidence has the ability to support or
contradict statements given by eyewitnesses and/or suspects. The information obtained from
physical evidences recovered can also lead to the information and also confirms the
reconstruction of a crime to a jury.

FORENSIC SCIENCE PAPER NO.7 : Criminalistics and Forensic Physics

MODULE NO.5: Types, Significance and Classification of
Physical Evidence
 2.3 Processing of Physical Evidence
The processing of physical evidence collected by the crime scene is a step by step process. The
following are the stages to be followed while processing investigation of a crime.

1. Discovering physical evidence

2. Recognizing physical evidence
3. Examining physical evidence
4. Collecting physical evidence
5. Recording physical evidence
6. Identifying physical evidence
7. Packaging, conveying and storing physical evidence
8. Exhibiting physical evidence in court
9. Disposing of physical evidence when the case is closed

3. Types of Physical Evidences

Various types of Physical evidences are encountered at the crime scene. Few of them are
mentioned below and discussed in detail:

1. Blood
2. Semen
3. Saliva
4. Documents
5. Explosives
6. Firearms and ammunition

Other important Physical evidences are:-

7. Fingerprints
8. DNA Evidence
9. Skeletal Evidence
10. Petroleum products
11. Plastic bags
12. Plastic, rubber, and other polymers
13. Vehicle lights
14. Wood and other vegetative matter

FORENSIC SCIENCE PAPER NO.7 : Criminalistics and Forensic Physics

MODULE NO.5: Types, Significance and Classification of
Physical Evidence
 Now let us discuss few important physical evidences in detail:-

3.1 Blood
Blood is a bodily fluid in animals that delivers necessary substances such as nutrients and
oxygen to the cells and transports metabolic waste products away from those same cells.

Blood is often encountered at many crime scenes specifically in heinous crimes such as murder,
rape, suicide, hit and run etc. Many potential details can be obtained from blood evidence
regarding the crime scene which can further be used in the investigation. DNA, proteins & cells
are the important component of blood which allows the laboratory to perform examination.
Useful information can be obtained from blood.

The examinations be can done to determine

1. Source of Origin- If the source of origin of blood is human or non-human.

2. Specific Animal Family- The specific animal family can be determined for non-human
blood.

3. Exclusion and Inclusion of Possible suspects- If blood belongs to Human origin, then it
can be compared with the specimen blood for exclusion or inclusion of possible suspects.

3.2 Semen
Semen (seminal fluid) is an organic fluid that may contain spermatozoa. It is secreted by the
sexual glands and other sexual organs of male or hermaphroditic animals and
can fertilize female ova.

In case of sexual offenses and when the perpetrator is male then semen stains are usually
encountered at the crime scene. The stains may be found on the body of victim, clothing’s, rags,
upholstery, beddings and on other sources also.

FORENSIC SCIENCE PAPER NO.7 : Criminalistics and Forensic Physics

MODULE NO.5: Types, Significance and Classification of
Physical Evidence
 The following are the few steps required while collection of Seminal Stains from the crime
scene area:

1. All the stained material under suspicion should be recovered carefully.

2. In order to avoid cross contamination of evidences and to prevent their loss, each item
should be separately packaged.
3. All damp stains should be air-dried.
4. The location of moist stain on the evidences itself must be marked because once air dried
it may not be visible.
5. Use clean paper; spread it under the item to catch any kind of debris which may be
dislodged during the drying process, and between items hanging next to each other so as
to avoid the possibility of the evidence getting contaminated.
6. Avail assistance of forensic staff to recover the stains in case when semen stains are on
object that cannot be easily submitted to the laboratory.

3.3 Saliva
Saliva is a watery secretion that is secreted by the salivary glands present in the mouth of
animals. Human saliva contains 99.5% - Water and 0.5% of electrolytes, mucus, glycoproteins,
enzymes, and antibacterial compounds.

Saliva stains are not usually evident from a visual examination. Certain type of evidences
frequently contains traces of saliva such as cigarette butts, gummed surfaces of envelopes,
chewing gum, bite marks, ski and/or nylon masks, etc.

3.3.1 Few points to be kept in consideration while collecting Saliva Evidence

If the saliva stained object is transportable then it is advisable to submit the object intact. And in
case it is not possible to transport the stained object e.g. bite mark on a body then following
points might be considered while collecting saliva stain:

1) Moisten a sterile cotton swab with distilled or tap water.

2) Shake the swab to remove excess water.
3) Gently swab the suspected saliva stain.
4) Allow the swab to thoroughly air-dry prior to packaging in a paper envelope and seal.

FORENSIC SCIENCE PAPER NO.7 : Criminalistics and Forensic Physics

MODULE NO.5: Types, Significance and Classification of
Physical Evidence
 In order to collect the negative control select an unstained area and collect a sample in the same
manner as described above. This swab will serve as a negative control.

3.4 Documents

Section 3 of Indian Evidence Act describes Document as:

Document means any matter expressed or described upon any substance by means of letters,
figures or marks, or by more than one of those means, intended to be used, or which may be
used, for the purpose of recording that matter.

The role of document examiner is to ascertain if the questioned sample originated from the same
source as that of known item(s) followed by presenting their opinion on the matter in court as an
expert witness. A document examiner also determines what has happened to a document, its
absolute/relative date of production, decipher information on the document that has been
obscured, obliterated or erased.

3.4.1 Types of document examined

Documents play an important in our daily lives including our business and personal affairs.
Authenticity of almost any kind of document can be questioned.
In broadest sense a document is anything bearing marks, signs or symbols which conveys
message or meaning to someone. It includes traditional paper documents, things like graffiti on a
wall, stamp impressions, or covert markings hidden in a written letter, among other things etc.
Any material or sheet of paper bearing handwriting or mechanically-produced text such as a
ransom note, a forged cheque or a business contract is regarded as a document. In other words it
may be some material which is not normally thought of as a 'document'.
A forensic document examiner conducts examinations and comparisons which can be quite
diverse. The following examinations are usually carried out by a forensic document examiner:-
 Handwriting (cursive / printing) and Signatures
 Typewriters, Photocopiers, Laser printers, Ink Jet Printers, Fax machines
 Chequewriters, Rubber stamps, Price markers, Label makers
 Printing Processes

FORENSIC SCIENCE PAPER NO.7 : Criminalistics and Forensic Physics

MODULE NO.5: Types, Significance and Classification of
Physical Evidence
  Ink, Pencil, Paper
 Alterations, additions, erasures, obliterations
 Indentation detection and/or decipherment
 Sequence Determination
 Physical Matching

3.4.2 Handwriting examinations

Generally, there are three stages in the process of handwriting examination. In brief, they are:

1. Analysis
2. Comparison (questioned item against the known standard)
3. Evaluation
4. Optionally, the fourth step consisting of verification/validation or peer review may also
be there

3.4.3 Tools for document examination

 Excellent eyesight
 Hand lens
 Stereomicroscope
 Electrostatic detection device (EDD)
 Video Spectral Comparator (VSC)
 Docubox Dragon
 Docucenter
 Raman Spectrophotometer

FORENSIC SCIENCE PAPER NO.7 : Criminalistics and Forensic Physics

MODULE NO.5: Types, Significance and Classification of
Physical Evidence
 3.5 Explosives
An explosive material, also called an explosive, is a reactive substance that contains a great
amount of potential energy that can produce an explosion if released suddenly, usually
accompanied by the production of light, heat, sound, and pressure. Or in other words, an
explosive is a substance, may be an element, a compound or mixture, which is capable of
exerting pressure on its surroundings on explosion/transformation. Forensic Science plays a role
in relation to explosives. Explosives are studied by forensic personnel mainly related to mass
destruction episodes where bombs are used for illicit activities. The explosive residues collected
from the crime scene are examined for many causes specially in order to identify the explosive
material, the source and intention of explosion. An explosive have many applications which are
legal and do not cause harm to any animal or human being.

Legitimate Uses: The legitimate uses of explosives include blasting rocks in cases of mining,
explorations of oil fields, space craft and satellites, for construction purposes of roads and
railway line etc., in fireworks displays, and may also be used as Military Explosives.

Illegitimate Uses: The criminals are using the explosives for causing destruction to individuals
or a nation by blasting bombs. The illegitimate use of explosive cause high destruction to the
integrity of any nation and is severely punishable under Indian Penal Code, Explosive Act and
The Explosives Substance Act.

The some common examples of explosives are RDX, TNT, TETN, ANFO, Dynamite etc.

Forensics plays an important role in the investigation of explosions where

explosive substances/materials are the main ingredients. Explosives can be
detected prior to explosions (during trafficking) and also after the explosion by
forensic spot tests and also by hi-tech forensic analytical tools. In simplest term we can define an
explosion as rapid increase in volume and release of energy along with the generation of high
temperature and release of gases.

Due to the presence of organic compounds containing -NO2, -ONO2 and -NHNO2 groups and
others an explosion is a spontaneous chemical reaction which is driven by great release of heat
and energy. This type of explosion is known as Chemical Explosion.The chemical explosion is
of three types- Decomposition, Deflagration and Detonation.

FORENSIC SCIENCE PAPER NO.7 : Criminalistics and Forensic Physics

MODULE NO.5: Types, Significance and Classification of
Physical Evidence
 The chemical decomposition of an explosive is a slower process which takes place in storage.
This may take years, days, hours, or a fraction of a second. The chemical decompositon of an
explosive is categorised in two types-Deflagration and Detonation.

Delagration is defined as the successive layer by layer burning of the explosive substance and
only low explosive undergo this process.

In Detonation of an explosive, it is propagated by an explosive shock wave traversing the

explosive material. The shock front is capable of passing through the high explosive material at
great speed, typically thousands of metres per second. Detonation takes place in High
Explosives.

The Explosives can be classified on the basis of composition, velocity, sensitivity and physical
forms. But broadly explosives are of three types. Low explosives, High Explosives and
Miscellaneous which we can further divide into Homemade Explosives, Nuclear Explosives and
others.

Availability and cost, Sensitivity, Sensitivity to initiation, Velocity of detonation, Stability,

Power, performance, and strength, Brisance, Density, Volatility, Toxicity, Explosive train,
Oxygen balance and Chemical composition are some of the important characteristics of an
explosive which are very important to determine whether the explosive is suitable for a particular
use.

There are some important rules which an investigating officer must keep in mind for Evidence
Collection. Few of them are mentioned below

a) Make Sure That There Are No Suspected Devices

b) Use Aerial Photography
c) Use Wire Mesh Screens to collect post blast residues
d) Do not- Handle potential explosives yourself
e) Clear and secure the area from unauthorized persons
f) Call the Bomb Squad
g) Use Bomb Disposal Suit
h) Always photograph the item "as found”
i) Always note the Evidence and its location
j) Do not restrict to a limited area of blast scene.
k) Always wear latex gloves to collect evidence.
l) Search far and wide from Epicenter

FORENSIC SCIENCE PAPER NO.7 : Criminalistics and Forensic Physics

MODULE NO.5: Types, Significance and Classification of
Physical Evidence
 m) Always use clean, suitable, and unused containers.
n) Always label properly.
o) Always change gloves between collecting different items.
p) While collecting different evidences, clean tools must be used.
q) Remember to store evidences in a safe location.
r) Also remember to maintain the chain of custody.
s) Size of explosive does Not Matter
t) Collect soot deposits
u) Interview the Witness
v) Search for explosive device/bomb fragments.

3.6 Ballistics Evidence such as Firearms and ammunition

The range of evidence in firearms-related cases can be as small as a piece of a bullet fragment
which has rifling marks or as large as hundreds of bullets and cartridge cases and numerous
firearms.

A firearm is a portable gun, being a barreled weapon that propels projectiles due to the expansive
force of the gases whereas ammunition may be defined as a propellant and projectile, or anything
that can be used in combat including bombs, missiles, landmines and anti-personnel mines.

A ballistics expert is a forensic specialist who is responsible for collecting and analyzing
ballistics-related evidence, which includes firearms and ammunition.
The Ballistics evidence which may encounter at the crime scene may include:
 Firearms
 Spent cartridges
 Spent shell casings/bullets
 Shot shell wadding
 Live ammunition
 Clothing

FORENSIC SCIENCE PAPER NO.7 : Criminalistics and Forensic Physics

MODULE NO.5: Types, Significance and Classification of
Physical Evidence
 3.6.1 Firearm Evidence Collection

Firearms evidence can be recovered in a number of ways and areas. Crime scene professionals
discover firearms from the scene of shooting and sends them to laboratory..

After conducting proper documentation and photography of the crime scene and firearm
evidences such as bullets, bullet fragments, cartridge cases, etc., are generally collected and sent
to the laboratory.

Bullet evidence can also be obtained at autopsy or in an emergency room setting. In these cases
the sample should be marked as a biohazard and then sent to the laboratory. Each laboratory has
written procedures for packaging and submitting evidence.

Bullets/slugs that do not strike a person are often imbedded into a nearby surface such as
wood/drywall. This evidence is best gathered by cutting out a section of the material and
submitting it to the laboratory to allow a firearm examiner to carefully extract it. This prevents
adding or destroying any markings that could be crucial to identifying or matching the suspected
firearm.

3.6.2 Analysis of firearm Evidence

A well-trained firearms examiner should perform the evaluation and comparison of this
evidence.
a) The marks left on ammunition may help in determining which firearm was used to fire
the bullet.
b) From the bullets fired to calibers and rifling patterns it is possible to identify the
characteristics of firearms.
c) Cartridges and cases are analyzed to search for signs of firing pin impression, ejector
marks, extractor marks, and other tool marks.
d) Even from small samples, information can be developed to indicate the type of firearm
used and possibly identify the actual firearm that was used.
e) Other firearms evidence that could be found at a shooting scene includes shot shell wads
and shot pellets; these can indicate the gauge of the shotgun.
f) Wads and pellets can be gathered and preserved in the same manner as bullets and
cartridge cases.

FORENSIC SCIENCE PAPER NO.7 : Criminalistics and Forensic Physics

MODULE NO.5: Types, Significance and Classification of
Physical Evidence
 g) By examining wadding materials, the examiner may be able to determine the gauge of the
shotgun, the manufacturer or marketer, a range of possible shot sizes based on
impressions in the shot shell wad, individual characteristics (in some cases).

4. Summary

1. Discovering, recognizing, examining, collecting, recording, identifying, packaging,

conveying & storing, exhibiting and disposing of physical evidence are the few steps in
processing of physical evidence collected from the crime scene
2. Various types of Physical evidences encounters at the crime scene such as blood, Semen,
Saliva, Documents, Explosives, Firearms and ammunition, Fingerprints, DNA, Skeletal
Evidence, Petroleum products, Plastic bags, Plastic, rubber & other polymers, Vehicle
lights, Wood and other vegetative matter etc.
3. Blood is a bodily fluid in animals that delivers nutrients and oxygen to the cells and
transports metabolic waste products away from those same cells.
4. Potential details regarding the crime scene can be obtained from blood evidence which
can support the investigation.
5. DNA, proteins & cells are the important component of blood which allows the laboratory
to perform examination.
6. Semen is an organic fluid that may contain spermatozoa.
7. Semen is secreted by the sexual glands and other sexual organs of male or
hermaphroditic animals and can fertilize female ova.
8. Seminal stains are usually encounters in sexual offenses and when the perpetrator is a
male.
9. The seminal stains may be found on the body of victim, clothing’s, rags, upholstery,
beddings and on other sources also.
10. All the stained material under suspicion should be recovered carefully.
11. In order to avoid cross contamination of evidences and to prevent their loss, each item
should be separately package.
12. All damp seminal stains should be air-dried.
13. The location of moist seminal stain on the evidences itself must be marked.
14. Use clean paper, spread it under the item to catch any kind of debris which may be
dislodged during the drying process, and between items hanging next to each other to
prevent cross contamination.
15. Avail assistance of forensic staff to recover the stains in case when semen stains are on
object that cannot be easily submitted to the laboratory.

FORENSIC SCIENCE PAPER NO.7 : Criminalistics and Forensic Physics

MODULE NO.5: Types, Significance and Classification of
Physical Evidence
 16. Human saliva contains 99.5% water and 0.5% of electrolytes, mucus, glycoproteins,
enzymes and antibacterial compounds.
17. Saliva stains evidences are usually found at cigarette butts, gummed surfaces of
envelopes, chewing gum, bite marks, ski and/or nylon masks, etc.
18. Submit the object intact if the saliva stained object is transportable.
19. If it is not possible to transport the stained object e.g. bite mark on a body then moisten a
sterile cotton swab with distilled or tap water, shake the swab to remove excess water,
Gently swab the suspected saliva stain and allow the swab to thoroughly air-dry prior to
packaging in a paper envelope and seal.
20. Select an unstained area in order to collect the negative control and collect a sample in
the same manner as the saliva stains. This swab will serve as a negative control.
21. Section 3 of Indian Evidence Act describes Document as “Document means any matter
expressed or described upon any substance by means of letters, figures or marks, or by
more than one of those means, intended to be used, or which may be used, for the
purpose of recording that matter”.
22. Document can also be described as “Anything bearing marks, signs or symbols which
conveys message or meaning to someone including traditional paper documents, things
like graffiti on a wall, stamp impressions, or covert markings hidden in a written letter,
among other things etc.”
23. A questioned document may be a sheet of paper bearing handwriting or mechanically-
produced text such as a ransom note, a forged cheque or a business contract.
24. A forensic document examiner conduct examinations and comparisons usually for
Handwriting (cursive / printing) and Signatures, Typewriters, Photocopiers, Laser
printers, Ink Jet Printers, Fax machines, Cheque writers, Rubber stamps, Price
markers, Label makers, Printing Processes, Ink, Pencil, Paper, Alterations, additions,
erasures, obliterations, Indentation detection and/or decipherment, Sequence
Determination and Physical Matching.
25. Generally, there are three stages in the process of handwriting examination.
26. Excellent eyesight, Hand lens, Stereomicroscope, Electrostatic detection device, Video
Spectral Comparator, Docubox Dragon, Docucenter, Raman Spectrophotometer etc. are
the tools for document examination.
27. An explosive material, also called an explosive, is a reactive substance that contains a
great amount of potential energy that can produce an explosion if released suddenly,
usually accompanied by the production of light, heat, sound, and pressure.
28. An explosive is a substance, may be an element, a compound or mixture, which is
capable of exerting pressure on its surroundings on explosion/transformation.

FORENSIC SCIENCE PAPER NO.7 : Criminalistics and Forensic Physics

MODULE NO.5: Types, Significance and Classification of
Physical Evidence
 29. The legitimate uses of explosives include blasting rocks in cases of mining, explorations
of oil fields, space craft and satellites, for construction purposes of roads and railway line
etc., in fireworks displays, and may also be used as Military Explosives.
30. The illegitimate use of explosive includes blasting bombs which cause heavy loss to life,
property as well as to the integrity of any nation and is severely punishable under Indian
Penal Code, Explosive Act and The Explosives Substance Act.
31. RDX, TNT, TETN, ANFO, Dynamite etc. are few examples of explosives.
32. Explosives can be detected prior to explosions (during trafficking) and also after the
explosion by forensic spot tests and also by hi-tech forensic analytical tools.
33. An explosion is a rapid increase in volume and release of energy along with the
generation of high temperature and release of gases.
34. Due to the presence of organic compounds containing -NO2, -ONO2 and -NHNO2 groups
and others an explosion is a spontaneous chemical reaction which is driven by great
release of heat and energy. This type of explosion is known as Chemical Explosion.
35. Decomposition, Deflagration and Detonation are the three types of chemical explosion.
36. The chemical decomposition of an explosive is a slower process which take place in
storage and may take years, days, hours, or a fraction of a second.
37. Deflagration and Detonation are two rapid forms of Chemical decomposition.
38. Broadly explosives are of three types. Low explosives, High Explosives and
Miscellaneous which we can further divide into Homemade Explosives, Nuclear
Explosives and others.
39. Availability and cost, Sensitivity, Sensitivity to initiation, Velocity of
detonation, Stability, Power, performance, and strength, Brisance,
Density, Volatility, Toxicity, Explosive train, Oxygen balance and Chemical
composition are some of the important characteristics of an explosive which are very
important to determine whether the explosive is suitable for a particular use or not.
40. A firearm is a portable gun, being a barreled weapon that launches one or more
projectiles often driven by the action of an explosive force.
41. Ammunition is a propellant and projectile, or anything that can be used
in combat including bombs, missiles, landmines and anti-personnel mines.
42. A ballistics expert is a forensic specialist who is responsible for collecting and analyzing
ballistics-related evidence.
43. Firearms, Spent cartridges, shell casings/bullets, Shot shell wadding, live ammunition and
Clothing are the ballistics evidence which may encounter at the crime scene.
44. Firearms evidence can be recovered at shooting scenes by crime scene investigators and
sent to the laboratory.
45. Bullets, bullet fragments, cartridge cases, shot shell wadding, etc., are normally collected
individually after proper documentation/photography and sent to the laboratory.

FORENSIC SCIENCE PAPER NO.7 : Criminalistics and Forensic Physics

MODULE NO.5: Types, Significance and Classification of
Physical Evidence
 46. Bullet evidence can also be obtained at autopsy or in an emergency room setting. In these
cases the sample should be marked as a biohazard and then sent to the laboratory.
47. The marks left on ammunition may help in determining which firearm was used to fire
the bullet.
48. From the bullets fired to calibers and rifling patterns it is possible to identify the
characteristics of firearms.
49. Cartridges and cases are analyzed to search for signs of firing pin impression, ejector
marks, extractor marks, and other tool marks.
50. Wads and pellets can be gathered and preserved in the same manner as bullets and
cartridge cases.

FORENSIC SCIENCE PAPER NO.7 : Criminalistics and Forensic Physics

MODULE NO.5: Types, Significance and Classification of
Physical Evidence
 SUBJECT FORENSIC SCIENCE

Paper No. and Title PAPER No.7: Criminalistics and Forensic Physics
Module No. and Title MODULE No.6: Types, Significance and Classification of
Trace Evidence
Module Tag FSC_P7_M6

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 6: Types, Significance and Classification of
Trace Evidence
 TABLE OF CONTENTS

1. Learning Outcomes
2. Types of evidences
3. Trace Evidence- An Introduction
4. Types of Trace Evidences
5. Summary

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 6: Types, Significance and Classification of
Trace Evidence
 1. Learning Outcomes

After studying this module, you shall be able to learn about-

 Various types of evidences,

 Trace Evidence in detail,
 The different types of Trace Evidences

2. Types of Evidence

Broadly evidence can be divided into three i.e. Testimonial Evidence, Physical Evidence
and Trace Evidence.

Let us understand these evidences in detail.

1. Testimonial Evidence:- These are the evidences in oral or written statements often
given by the people who witnessed an event/crime. This evidence is often given to
police as well as court testimony.

2. Physical Evidence:- These are the evidences which are any material items that
would be present at the crime scene, on the victims, or found in a suspect’s
possession.
3. Trace Evidence:- These are the physical evidence which are found in small but
measurable amounts. Few examples of trace evidences are strands of hair, fibers, or
skin cells.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 6: Types, Significance and Classification of
Trace Evidence
 3. Trace Evidences-An Introduction

The trace evidence can be obtained on the culprit, victim, crime scene, weapon, vehicle etc.
The culprit & victim may carry traces on his clothes, on his shoes, in his hair, underneath
his nails, in his sexual body parts (in case of sexual offences) etc. The victim may also
carry powder residues in case of shooting. In case of killing by poison the needle marks or
poison traces at the administration point may also be found.

Most of the trace evidence is encountered at the crime scene such as saliva or cigarette
stud, on cups, glasses, dust, body fluids, fibers etc. Trace evidence such as blood, skin, and
flesh may be found sticking to the weapon (i.e. firearm in suicide or close contact murders).

Locating trace evidence is usually a tedious task due to the small quantity of evidence
encountered. Due to minute nature of evidence the collection of trace evidence needs more
precautions compared to other types of evidence. Besides trained eye & brain the help of
magnifying glass, strong light & UV lamp can also be taken.

Collection:-Tapping, vacuuming, hand picking, scraping are few techniques for collection
of trace evidence.

Packaging:- Packaging of Evidence needs care in order to prevent loss or contamination.

The different packaging material is required for individual trace evidence.

4. Types of Trace Evidences

Different types of trace evidences encounters at the crime scene. Few of them are
mentioned below and discussed in detail:

1) Hair
2) Fiber
3) Soil
4) Paint

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 6: Types, Significance and Classification of
Trace Evidence
 5) Gunshot residue
6) Glass
7) Tool Marks

Other important Trace evidences are:-

8) Tire Tracks
9) Bite Marks
11) Drug
12) Injuries (lacerations, contusions, etc.)
13) Fingernail scrapings
14) Fracture marks
15) Insects

Now let us discuss few important trace evidences in detail:-

1) Hair

Hair on brush often encountered at the crime scene. Forensic investigation of hair can tell
investigator whether the hair belongs to human or animal. If the source of origin of hair is
human then the specific part of the body from where the sample has originated can also be
find out. The hair evidence is usually tested to determine not only the color, shape and
chemical composition of the hair but also the race of the source individual. The presence of
dyes, hair treatment, toxins is noted. The gathered information assists investigating officer
in inclusion or exclusion of particular individuals. If the hair has a follicle (root) attached
then the DNA testing may be used to identify an individual.

Collection:- The collected hair evidences are sent to the laboratory along with the control
samples from a suspected individual. While collecting control samples make sure the hair
from all parts of the head are obtained. For pubic hair, the area should be combed for
foreign hairs prior to sample collection. Hair samples are primarily collected using
tweezers.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 6: Types, Significance and Classification of
Trace Evidence
 2) Fiber

Fiber is a natural or synthetic string which is used as a component of composite materials.

They are usually knotted into sheets to make products such as paper, papyrus, or felt. Other
materials are also manufactured from Fibers. Fiber evidence is useful in crime scene
investigation because their origin can be identified. However, fibers are very mobile and
can become airborne, get brushed off or fall from clothing. Fiber evidence can tell a lot
about crime if processed correctly. A carpet fiber on a person’s shoe can indicate the
individual’s presence at a crime scene. Fiber evidence is usually found in fabric abrasions
or caught in torn materials or other areas on hit-and-run vehicles, caught in torn screens,
broken glass, or other locations in some burglary cases. To determine whether fibers and
threads belongs to same source or not the same obtained from the body of suspects clothing
can also be compared.

Each collected article of clothing of each individual or other object must be packed
separately. Set each garment on a clean paper sheet and roll separately in the paper. Do not
forget to mark each exhibit. The comparison may have no value if the clothing of one
subject touches the clothing of another. Thread or large fibers are often picked up with the
fingers and placed in a paper bindle, and then in a coin envelope, which can be sealed and
marked. Loose fibers should not be placed directly into a mailing envelope since they can
be lost from this type of envelope. Examination of fibers is usually done to find out the
color or type of fiber. Such kind of examinations will sometimes indicate the type of
garment or fabric from which they originated. It may help an investigating officer in
proceedings. If the fibers are short or few in number, and if it is possible to do so, wrap the
area or the entire item containing the fibers in paper. The whole exhibits are then sent to the
Laboratory. When fibers or threads are recovered, always send all clothing of persons from
which they might have originated to the Laboratory for comparison purposes.

Fibers are prove very much helpful in cases of sexual offenses, assaults etc. In such cases it
may be possible to indicate or demonstrate contact between two individuals or between one
other individual and some other object, such as a car seat, by comparing fibers. Such
examinations are only of value when it is known no contact occurred between the two
individuals or an individual and some other object prior to, or subsequent to, the offense.

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MODULE No. 6: Types, Significance and Classification of
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 3) Soil

Soil is a composite mixture of material. The soil can be characterized with the help of
composition of minerals, the size and shape of grains. The soil or dried mud is usually
collected from the suspects clothing or shoes or an automobile may link a suspect or object
to the crime scene when compared to the soil there. The questioned soil can be analyzed
even without the crime scene and helps in finding the place where the crime was
committed. The chemical and physical properties of soil are usually looked for.

4) Paint
Paint is of high value evidence due to availability of painted surfaces in wide range &
variety of layered colors, luster & types. Paint evidence is usually transferred when one
vehicle hits another vehicle, a pedestrian or a building can be matched to potentially
identify the car in question. In a crime related to property where a tool is used to break into
a building, paint transferred to or from the tool can connect the tool to the location.
Analyzing automotive paint can identify the make, model and sometimes the year of a
vehicle.

Collection: To collect paint, investigators document the scene, then peel off, or excise,
small amounts of paint from the source.

5) Gunshot residue

Gunshot residue (GSR) is residue deposited on the hands and clothes of shooter. GSR is
basically composed of burnt and un-burnt particles from the explosive primer,
the propellant and possibly fragments of the bullet, cartridge case, and the firearm.
The clothing and skin of people is usually tested for GSR to determine if they were near a
gun when it discharged or not. An approximate distance of 3-5 feet can be travelled by
GSR. Only few trace particles may be present at the farthest distance.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 6: Types, Significance and Classification of
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 6) Glass

Glass is an amorphous (non-crystalline) solid material which is often transparent. Glass has
an extensive practical, technological, and decorative usage in things like tableware,
window panes etc. Traces of glass can often become a source of forensic evidence.
Windows are frequently broken in burglaries, headlights in hit-and-run cases, and bottles or
other objects may break or leave fragments on personal belongings of suspects involved in
various types of crimes. Glass is encountered as evidence in various forms such as vehicle
windows, architectural windows, containers, headlamps, and mirror glass. The examiners
compare samples of glass found on suspects or found at the scene of a crime with a
suspected source of known origin. The physical and optical properties of color, thickness,
density, and refractive index are measured.

Glass examinations may reveal:

a) Whether questioned or control sample belongs to same source or not.

b) The type of glass can also be find out whether tempered glass, container glass etc.
c) The direction of force used to break a window whether from inside or outside.
d) The order of shots fired into a window or windshield.

Recovery of Evidence Samples

1. Wrap shoes/clothing or other objects contaminated with glass in paper before

submitting to the laboratory for examination.

2. All glasses found at hit and run scenes should be recovered. As there is a possibility
that all glass found at hit-and-run scenes should be recovered. The search for glass
samples should not be restricted to the point of impact. Headlight glass may be
dropped off at some distance away as the car leaves the crime scene. Use different
containers to collect glass from different locations. All glass evidences found at the
crime scene should be collected because more than one type may be present. In
addition, if just a few representative samples are saved, individual pieces that could
be physically matched with glass remaining in the headlight shell of the suspected
vehicle may be overlooked.

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 3. The glass pieces collected from different locations must be package into different
containers. Mark clearly the outside packaging as to the location and description of
the evidence.

4. Label large glass pieces with orienting marks (e.g. up/down, inside/outside) when
applicable.

5. A rigid container must be used to collect and package a large glass piece.

6. The broken or fractured edges of the glass must be protected from any additional
damage or rupture.

7. Depending on the size, glass pieces can be packaged in envelopes, bags, or in paper
folds.

8. Place the small glass particles onto the adhesive of a Post-It note and use a pen to
circle around it.

9. Glass pieces that are a little bigger can be packaged in envelopes or bags, and then
secured in a padded envelope to protect from further breakage or injury to those
handling the evidence.

10. Fold the note in half, covering the glass particle(s), and then put the folded
Post-It note in a paper envelope.

11. Small particles of Glass may found on the clothing, sole/tops of shoes & cuffs or
lower portion of pants of an individual who breaks a window forcefully.

12. In order to prevent dislodging of small glass particles collect clothing items (with
small glass particles) with caution not to shake or handle the clothing more than
necessary.

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MODULE No. 6: Types, Significance and Classification of
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 13. If the clothing is stained with biological material, allow the clothing to air-dry on a
clean, dry surface and package in a paper bag.

14. Package unstained clothing in a plastic bag carefully sealing all possible openings.

15. The suspects' hair can be combed over white paper to recover any glass particles
that may be present. Fold the paper so that it prevents loss of the glass particles,
and package in a paper envelope, or bag.

Standards for Comparison

 Windows: Send the whole window, if the broken window is small or all glass
remaining to the Laboratory. If the window is large, recover several samples from
different areas of the window. If the evidence glass is large enough for physically
matching the broken edges or comparing the fracture lines, hackle marks, surface
abrasions or contamination, the whole broken window is necessary.

 Auto Glass - Auto Headlights: All glass remaining in the shell should be
recovered. If it is suspected that a new glass has been installed, this should be
removed and a careful examination made for small chips remaining in the shell
from the previous lens which is broken. In such cases, also submit the new lens to
the Laboratory.

Collection and Packaging of Glass Standards

 A comparison of evidence glass to a possible source requires the submission of

glass standards. If possible, submit the entire item in packaging that reduces the
chance for further breakage.
 Large windows may require a sampling of glass from several different spots, as
there may be variation of physical properties even within a single glass pane.

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MODULE No. 6: Types, Significance and Classification of
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  Vehicle windshields and some structural glass may be double paned, meaning that
two different panes of glass are present. Standards must be collected from different
areas on both glass panes. Package the standards from each pane separately.
 For window glass standards, collect the glass that is still adhering to the window
frame when possible. Collecting glass standards from the ground increases the
likelihood of introducing contaminant glass into the standard.

7) Tool Marks

A criminal often uses tools to commit a crime usually to open a window, lock etc. A
criminal can be linked to a crime through the tool & tool marks collected from the scene
even after a long interval of time. No two tools even of the same make and batch made one
after the other will have identical surface and leave identical marks on the surface, cut,
grazed or scratched by them.

Tool marks are of various types such as indentations (caused by hammer, dies, punches,
metallic seal & stamp, stones etc.),scrapes (caused by cutting tools, chisels, can openers,
crow bars, screw drivers, pliers, shovels, wrenches etc.), saw marks, drilled holes, prints,
contact marks, broken and screwed parts.

Collection:- The original articles which bear questioned tool marks are collected. Before
removal the article must be documented. When it is not possible to collect the tool mark
then casts of Plasticine, dental mass, adhesive tape, latex and plastic solutions, woods
metal, Plaster of Paris are used to collect.

Packaging: - Package the article in cellophane envelope. Close the open ends and pack the
envelope with cotton wool or clean dry rag padding in a suitable container.

Standard: - Standard tool marks are prepared by the examiners preferably using similar
material in which the tool marks are found at the site.

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MODULE No. 6: Types, Significance and Classification of
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 5. Summary

1) Evidence can be classified into Testimonial Evidence, Physical Evidence and Trace
Evidence.
2) The trace evidence can be found on the culprit, victim, crime scene, weapon,
vehicle etc.
3) Tapping, vacuuming, hand picking, scraping are few techniques for collection of
trace evidence.
4) Various types of trace evidences encountered at the crime scene such as Hair, Fiber,
Soil, Paint, Gunshot residue, Glass, Tool Marks, Tire Tracks, Bite Marks, drug,
Injuries, Fingernail scrapings, Fracture marks & Insects.
5) Examination of hair can help in finding source of origin whether the hair is of
human or animal.
6) The DNA testing of hair can also be done to identify an individual in case the hair
has a follicle attached to it.
7) Hair samples are primarily collected using tweezers.
8) Fiber is a natural or synthetic string which is used as a component of composite
materials.
9) Fiber evidence is usually found in fabric abrasions or caught in torn materials or
other areas on hit-and-run vehicles, caught in torn screens, broken glass, or other
locations in some burglary cases.
10) Comparison of fibers and threads with suspects clothing can help in determining
whether or not both belong to same source.
11) Examination of fibers is usually done to determine the type or color of fiber.
12) Soil is a complex mixture of material i.e. vegetation, flora and fauna.
13) Paint evidence is usually transferred when one vehicle hits another vehicle.
14) In a property crime where a tool is used to break into a building, paint transferred to
or from the tool can connect the tool to the location.

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 15) Gunshot residue (GSR) is residue deposited on the hands and clothes of shooter.
16) The clothing and skin of people is usually tested for GSR to determine whether they
were near a gun when it discharged or not.
17) Glass is an amorphous (non-crystalline) solid material.
18) The examination of glass can also reveal if it has been obtained from the same
source or not, the number of rounds fired, type and make of the glass and the
direction of force used to break a window.
19) The packaging of glass as evidence can be done in paper bags and envelopes based
on the size of the glass pieces.
20) In case the clothes found in the scene of crime are not stained with any biological
material for example blood then it should be packed in plastic bag otherwise the
clothing should be air dried and packaged in paper bag.
21) Two tools of the same batch and same model will never leave marks that are
identical to each other.
22) Tool marks are of various types such as indentations, scrapes, and saw marks,
drilled holes, and prints, contact marks, broken and screwed parts.
23) The original articles which bear questioned tool marks are collected.
24) When it is not possible to collect the tool mark then casts of Plasticine, dental mass,
adhesive tape, latex and plastic solutions, woods metal and Plaster of Paris are used
to collect.
25) Standard tool marks are prepared by the examiners preferably using similar material
in which the tool marks are found at the site.

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MODULE No. 6: Types, Significance and Classification of
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 SUBJECT FORENSIC SCIENCE
Paper No. and Title Paper No. 7: Criminalistics and Forensic Physics

Module No. and Title Module No. 7: Collection, Care and Packaging of Evidence

Module Tag FSC_P7_M7

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.7: Collection, Care and Packaging of
Evidence
 TABLE OF CONTENTS

1. Learning Outcomes
2. Evidence encounter at the crime scene
3. Collection of Evidence
4. Packaging of Evidence

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.7: Collection, Care and Packaging of
Evidence
 1. Learning Outcomes

After studying this module, you shall be able to learn about the evidences which an
investigator may encounter at the crime scene, procedures and precautions to collect
evidence and how to package evidence.

2. Evidence Encounter at the Crime Scene

Depending on the crime occurred various types of evidences are recovered from the crime
scene. An investigating officer may encounter with:-

1. DNA evidence
2. Impression evidence (fingerprint, shoe print, etc.)
3. Blood, Semen, Saliva and other body fluids.
4. Firearms and ammunition (gun, bullet, shell, etc.)
5. GSR swabs from shooting victims
6. Arson evidence (flammables, ignition source, etc.)
7. Wood, and absorbent materials
8. Chemicals and controlled substances (drugs)
9. Trace evidence (hair, fibers, soil, etc.)
10. Documents
11. Storage devices such as Compact Disk, DVD’s, floppy disk, hard disk’s etc
12. Victim’s clothing
13. Fingernail scrapings

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.7: Collection, Care and Packaging of
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 14. Vaginal, anal, and oral swabs
15. Glass
16. Charred clothing or debris.
17. And other potential evidence

3. Collection of Evidence

An investigating officer should remain cautious while collecting evidence from the crime
scene. He should always keep in mind:

1) What evidence should be collected?

2) How to collect?
3) Whether the evidence collected, will support the investigation or not?

Collection of Evidence at the crime scene is a two-step procedure:-

– First, search for and collect large, obvious items.
– Collect smaller items of physical evidence next but the Evidence that is
easily lost or fragile is collected first.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.7: Collection, Care and Packaging of
Evidence
 An investigating officer should follow the following precautions while collecting
evidence:-

1. Evidence should not be removed from its source (or from its original place) when
possible.
2. Evidence should be packaged individually to prevent breakage, spoilage and
contamination with other evidences.
3. Mark all evidence as it is being collected if possible–or package and mark the
outside of the package.
4. Evidence should be marked with the recovering officer’s initials, the location (from
which the evidence is recovered) and the date of recovery.
5. A chain of custody must be maintained. A list of all persons who came into
possession of an item of evidence should be maintained in order to support the
investigation.
6. Always wear gloves–latex or rubber gloves in order to prevent the contamination of
DNA evidence.
7. Take great care (when handling evidence) not to destroy fragile fingerprints or other
impressions.
8. Any items with residual moisture or bodily fluids should be thoroughly air-dried
before packaging.
9. Each different piece of physical evidence must be packaged separately.
10. Evidence must be handled with forceps (gloved hands only) or similar tools.
11. Flashlights or ALS (alternate light sources) are used to help identify evidence for
collection.
12. Once identified and documented, the evidence must be collected, preserved,
packaged and inventoried in preparation for submission to the crime lab.
13. Reference/standard samples should be collected from relevant persons or from the
scene and are used for comparison.
14. Disposable gloves are always worn, and often changed, to protect evidence from
contamination.
15. Impression evidence (fingerprint, shoe print, etc.) may be Identified by sight, ALS
or chemical reagent or enhanced by use of special photographic techniques or by
chemical developers or collected by lifting tape or molding materials.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.7: Collection, Care and Packaging of
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 16. Biological evidence (blood, semen, etc.) may be identified by sight, ALS or
chemical reagent, collected with sterile swabs, Firearms and ammunition (gun,
bullet, shell, etc.), must be rendered safe for transport.
17. Arson evidence (flammables, ignition source, etc.) may be located by sight and
smell, place carpet, wood, and absorbent materials in clean paint cans and seal lid,
place flammable liquids in glass bottle with tight-fitting lid.
18. Chemicals and controlled substances (drugs) may be located by visual observation,
Chemical field tests are used to classify or identify them at the scene.
19. Trace evidence (hair, fibers, soil, etc.) May be extremely small or microscopic,
collect by forceps, tweezers, scraping, taping, or vacuuming, Document and collect
questioned and known samples, Work in conjunction with medical examiner for
homicide evidence collection.
20. The medical examiner or coroner will examine the victim to establish a cause and
manner of death and preserve tissues and organs for analysis.

They may also collect some or all of the following:

 Victim’s clothing
 Fingernail scrapings
 Body hairs
 Blood
 Vaginal, anal, and oral swabs
 Bullets or other objects inside the body
 GSR swabs from shooting victims

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.7: Collection, Care and Packaging of
Evidence
 4. Packaging of Evidence
Physical evidence must be handled and packaged in a way that prevents any change from
occurring. The evidence must be properly packaged according to type and should be
properly labeled and sealed with appropriate initials to maintain chain of custody. The
integrity of evidence is best maintained when it is kept in its original condition as found at
the crime scene. Trace evidence should not be removed from the objects they’re found on
unless it is impossible to transport the item. The well-prepared evidence collector will
arrive at a crime scene with a large assortment of packaging materials and tools ready to
encounter any type of situation.

Physical evidence must be collected and packaged correctly so it does not change from the
time it was collected to the time it is processed by the crime lab. Each item must be placed
in a separate container to prevent cross-contamination. The package should be clearly
labeled and sealed with evidence tape. Take entire piece of evidence as it is found at the
scene, if possible.

Wet blood should either dry first and then be scraped or can be collected on a swab.

1. Hair, glass, fibers, and other types of trace evidence should be store in
indestructible plastic pill bottles with pressure lids or in Beige envelopes, screw-
cap glass vials, or cardboard pillboxes.
2. Paper bags and boxes can be use for bigger and/or heavier pieces of evidence.
3. For powders such as drugs or others ordinary mailing envelopes should not be
used because powders will leak out of their corners.
4. Arson evidence is placed in clean paint cans.
5. Blood-stained things should be kept in paper bags or manila envelopes.
6. Blood-soaked clothing should not be reserve in air-tight vessels as the
surrounded moisture can cause the development of mildew and mold and
destroy the blood.
7. All clothing should be air-dried and independently put in storage in paper bags.
8. Charred clothing or debris on the contrary, must be stored in air-tight containers
so that evaporation of volatile petroleum residues does not occur.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.7: Collection, Care and Packaging of
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 9. All diverse article or like articles collected at various places should be placed in
isolated containers. Wrapping evidence independently averts damage by contact
and avoids cross-contamination.
10. Forceps and similar apparatus may have to be used to pick up small items.
11. Insignificant quantities of trace evidence may also be accessibly packed in a
cautiously folded paper, by what is said to be “druggist fold.”
12. Though pill bottles, vessels, containers, or beige envelopes are best universal
containers for all trace evidence, two mostly found at crime scenes warrant
special attention.
13. If bloodstained constituents are kept in airtight vessels, the accretion of moisture
may reassure the development of mold that can ruin the evidential importance
of blood.

14. In these cases, packaging paper, fawn envelopes, or paper bags are suggested
wrapping materials.
15. All evidence should be packaged separately.
16. New and unused packaging materials must be used.
17. Seal evidence using proper methods which prevent tampering.
18. Though these kinds of sealable parcels are good for powders and other dry
trace, bloodstains and bloodstained evidence is unlike.
19. Bloodstained evidence should not be packaged in airtight containers due to the
moisture content of the blood.
20. The blood will start to mold very quickly and this mold will damage the
evidence item and the associated bloodstains.
21. For damp or bloody items one should use:
a) Brown paper bags of appropriate size
b) Earthguard bags
c) Butcher paper that can be folded and properly taped shut.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.7: Collection, Care and Packaging of
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 22. Any items with residual moisture or bodily fluids should be thoroughly air-dried
and then packaged in a non-porous container such as paper or cardboard so as to
prevent the destruction of DNA by bacteria, mold, etc.
23. Arson evidence (flammables, ignition source, etc.) may be located by sight and
smell, place carpet, wood, and absorbent materials in clean paint cans and seal
lid, place flammable liquids in glass bottle with tight-fitting lid.
24. Chemicals and controlled substances (drugs) may be Located by visual
observation, Chemical field tests are used to classify or identify them at the
scene, Place liquids or solids in a screw cap jar or vial.

5. Chain of Custody
After all the collected evidences have been packaged properly they should be properly
labeled. After labeling the next step is to transport all the packed evidences to the crime lab
for forensic analysis or for further evaluation.

In order to maintain all items, a complete and correct chain of custody must be maintained
for all items.

This is not necessary that the evidence collector only will transport the evidence to the
laboratory. Often some other officer transports the evidence to the lab. That’s why
maintenance of chain of custody log must be maintained indicating the transfer of custody
to and from every individual who is involved in transporting or storing the evidence until it
gets to the crime lab. These include:

a) The collecting officer (who collects the evidence from crime scene),
b) The transportation officer (who transport the collected & packaged evidence
from Crime scene to the laboratory),
c) Any evidence storage officer if the evidence is stored prior to taking it to the lab,
d) Any further transportation officer,
e) Anyone who gets into the evidence for any reason,
f) The laboratory evidence collection person(s).
g) Any other person involved in the whole process.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.7: Collection, Care and Packaging of
Evidence
 Send all evidence (to the crime lab) registered or certified mail, return receipt requested, to
maintain the chain of custody.

6. Summary

1. Evidence should not be removed from its source or from its original place, if
possible.
2. Evidence should be packaged individually to prevent breakage, spoilage and
contamination with other evidences.
3. A chain of custody must be maintained. A list of all persons who came into
possession of an item of evidence should be maintained in order to support the
investigation.
4. Use of gloves either of latex or rubber is must in order to prevent the contamination
of DNA evidence.
5. While handling evidence great care is required in order to prevent destruction of
fragile fingerprints or other impressions.
6. Reference or Standard samples should be collected from relevant persons or from
the scene and are used for comparison.
7. Impression evidence (fingerprint, shoe print, etc.) may be Identified by sight,
Alternate Light Sources or chemical reagent or enhanced by use of special
photographic techniques or by chemical developers or collected by lifting tape or
molding materials.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.7: Collection, Care and Packaging of
Evidence
 8. Hair, glass, fibers, and other trace evidence should be store in unbreakable plastic
pill bottles with pressure lids or in Manila envelopes, screw-cap glass vials, or
cardboard pillboxes.
9. Blood-soaked clothing must not be stored in air-tight containers because the
trapped moisture may cause the growth of mildew and destroy the blood.
10. Each different item collected at different locations must be placed in separate
containers to prevent damage through contact and prevents cross-contamination.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.7: Collection, Care and Packaging of
Evidence
 SUBJECT FORENSIC SCIENCE

Paper No. and Title PAPER No.7: Criminalistics and Forensic Physics

Module No. and Title MODULE No.8: Submission of Evidence and Chain of
Custody
Module Tag FSC_P7_M8

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 8: Submission of Evidence and Chain of
Custody
 TABLE OF CONTENTS

1. Learning Outcomes
2. Evidence Collection

2.1 Evidence Marking and Packaging

3. Chain of Custody
3.1 Transfer of Evidence to Property Room
4. Summary

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 8: Submission of Evidence and Chain of
Custody
 1. Learning Outcomes

After studying this module, you shall be able to know-

 About the procedures of evidence management

 Do’s and don’ts while submitting evidence to laboratory for examination, and
 The maintenance of chain of custody.

2. Evidence Collection

The Investigator needs to make it sure that evidence must be collected in a systematic
and careful manner. The process of evidence collection begins with the preliminary
crime scene survey/walk-through, followed by a determination of the evidence collection
sequence to be used. There are various methods which can be adopted for the evidence
collection based on the type of crime scene. The evidence collection sequence may be
based on the following information:

 The scene location: whether the crime has occurred inside premises or within a
vehicle or it is an exterior one.
 The condition of the evidence: the condition of evidence (Whether the evidence is
fragile or stable) plays an important role in choosing which evidence collection
method is to be used.
 Weather conditions which might affect the scene or evidence within.
 Scene management considerations which may alter or contaminate the evidence.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 8: Submission of Evidence and Chain of
Custody
 Investigators should use the appropriate equipment when collecting evidence.
Equipments that are required for collection of evidences must be sterile so as to avoid
contamination of evidence. Various equipments are used to collect evidence.

Few of them are named below:

1. Latex gloves/nitrile gloves (N-DEX, non-latex):- helps in preventing

contamination as well as any kind of hazardous exposure to the hands of
personnel collecting evidence.
2. Forceps- Forceps and similar tools may have to be used to pick up small items.
3. Tweezers
4. Scalpels
5. Swabs
6. Paper bags
7. Plastic bags
8. Cardboard boxes
9. Wrapping paper
10. Hand tools
11. Thermometer

2.1 Evidence Marking and Packaging

Evidences collected from the scene of crime or received during the investigation of crime
scene should be catalogued and packaged before leaving the scene to prevent loss or
cross-contamination. Mark the item of evidence when possible. Evidence which cannot
be marked, such as soil, hair and stains, should be placed in an appropriate container or
envelope.

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MODULE No. 8: Submission of Evidence and Chain of
Custody
 An important point that is to be kept in mind is that the evidences marked directly might
result in interference with the forensic analysis and hence marking should always be
done on outer packaging. When marking evidence directly, include the following:

 Case number
 Item number
 Date recovered or received
 Investigator’s initials

Evidence that has been inventoried, marked and prepared for submittal (or to be returned
to the investigating agency) is packaged in an appropriate container and labeled per
agency protocol.

A trained investigator or evidence collector arrives at the crime scene with the all types
of packaging materials and tools ready to encounter any type of situation. In order to
prevent any change in evidence, the evidence must be packaged carefully. The type of
packaging depends on the type of evidence. The evidence must be properly packaged,
properly labeled and sealed with appropriate initials to maintain chain of custody. The
evidence must be packaged in its original condition as it is found at the crime scene. The
objects with the trace evidence must be sent as whole until unless it is not possible to
transport the whole item such as wall.

As sometimes it takes a long time for a crime lab to processed the evidence so it is
necessary that the evidence must be packaged in such a manner that the conditions such
as evaporation, breakage etc. should not change its condition. While packaging the
chances of cross contamination must be ended. Each item must be packaged in separate
container. Every package must be labeled with all the essential details such as Case FIR
No., Item No., Type of Evidence (fragile/stable) etc. After labeling the package must be
sealed with evidence tape. Take entire piece of evidence as it found on the crime scene, if
possible. New and unused packaging materials should be used. Evidence must be sealed
using proper methods which prevent tampering. For powders such as drugs or others
ordinary mailing envelopes should not be used because powders will leak out of their
corners.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 8: Submission of Evidence and Chain of
Custody
 1. Unbreakable Plastic pill bottles with pressure lids or in Manila envelopes, screw-
cap glass vials, or cardboard pillboxes- Used to store trace evidence such as hair
glass fiber etc.

2. Paper bags and boxes- Used to package larger and/or heavier pieces of evidence.

3. Clean Paint Cans- Used to store Arson evidence.

4. Paper bags or Manila envelopes- Used to store Blood stained materials/clothing

after air drying.

5. Air tight containers- used to store

a) Blood-soaked clothing because the trapped moisture may cause the growth of
mildew & mold and destroy the blood.

b) Charred clothing or debris on the contrary to avoid evaporation of volatile

petroleum residues.

6. Druggist Fold- Used to package small amounts of trace evidence.

7. Brown paper bags of appropriate size, Earth guard bags & Butcher paper that can
be folded and properly taped shut- Used to store damp or bloody items.

8. Non-porous container such as paper or cardboard- Used to store any items with
residual moisture or bodily fluids which should be thoroughly air-dried and then
packaged so as to prevent the destruction of DNA by bacteria, mold, etc.

9. Glass Bottle with tight-fitting lid- Used to place flammable liquids.

10. Screw Cap Jar or Vial- Used to place liquids or solids.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 8: Submission of Evidence and Chain of
Custody
 3. Chain of Custody

After careful collection of the evidence the next step of the investigator is to submit
evidence in laboratory for examination. In the whole process the maintenance of chain of
custody is very important.

The transfer of property or evidence from a crime scene investigator to any other
individual, agency or location is documented by having a chain of custody. The list of
information that is to be included in the chain of custody:

 List of evidence: the item number and a brief description.

 All transfers must include the date and time of transfer.
 The signature of the individual releasing the evidence to another individual or
location.
 The signature of the individual transporting the evidence.
 The signature of the individual receiving the evidence from another individual or
location.
 Reason for the transfer as needed.

After all the collected evidences have been packaged properly they should be properly
labeled. After labeling the next step is to transport all the packed evidences to the crime
lab for forensic analysis or for further evaluation.

The chain of custody is a tracking document beginning with detailed scene notes that
document where the evidence was received from or collected. The chain of custody is
initially established when an investigator takes custody of evidence at a crime scene, or
when evidence is received from an officer or detective at, or from, the crime scene. In
order to maintain all items, a complete and correct chain of custody must be maintained
for all items.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 8: Submission of Evidence and Chain of
Custody
 Notes should be prepared which comprises of documentation of recovery location, the
date and time of recovery and also the description of items, condition and whether any
unusual markings or alterations to the item was present during recovery.

This is not necessary that the evidence collector only will transport the evidence to the
laboratory. Often some other officer transports the evidence to the lab. That’s why
maintenance of chain of custody log must be maintained indicating the transfer of
custody to and from every individual who is involved in transporting or storing the
evidence until it gets to the crime lab. These include:

a) The collecting officer (who collects the evidence from crime scene),
b) The transportation officer (who transport the collected & packaged evidence
from Crime scene to the laboratory),
c) Any evidence storage officer if the evidence is stored prior to taking it to the lab,
d) Any further transportation officer,
e) Anyone who gets into the evidence for any reason,
f) The laboratory evidence collection person(s).
g) Any other person involved in the whole process.
h) Send all evidence (to the crime lab) registered or certified mail, return receipt
requested, to maintain the chain of custody.

3.1 Transfer of Evidence to Property Room

On many occasions the agencies transfers the evidence to a property room

aforementioned to its submission in a crime lab. Property room documentation or secure
electronic transfer is used when the investigator submits evidence to the property room.
The associated information may include the following:

 Agency case number

 Type of evidence

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 8: Submission of Evidence and Chain of
Custody
  Officer responsible for the investigation: the name, rank and identification
number of the officer for whom the evidence was recovered. The official
laboratory report is addressed to this officer
 Transporting officer: the name, rank, identification number and assignment of the
investigator
 Signature or other identifier of responsible officer and date prepared ; the date the
evidence is submitted to the property room
 Comment: the address where the incident was located, or where the evidence was
recovered

The list of the evidence/property may include:

 Number each evidence item sequentially

 Quantity of items included , e.g., 10 spent shell casings
 Serial number of the item, e.g., VCR, handgun.
 Item description.
 Status: e.g., submit for analysis, Hold, or RTC (releasable, return to claimant or
owner).

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MODULE No. 8: Submission of Evidence and Chain of
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 4. Summary

1. The evidence collection sequence may be based on the scene location, the
condition of the evidence, weather conditions etc.

2. Collection equipment that may come into contact with evidence should be sterile
to avoid contamination of evidence.

3. Mark all the item of evidence which must include Case number, Item number,
Date recovered or received & Investigator’s initials.

4. Evidence that has been inventoried, marked and prepared for submission is
packaged in an appropriate container and labeled per agency protocol.

5. The evidence must be packaged in its original condition as it was found at the
crime scene.

6. The objects with the trace evidence must be sent as whole until unless it is not
possible to transport the whole item such as wall.

7. The evidence should be packaged in such a manner that it should not lose the
potential information it is having due to the factors such as evaporation, breakage
etc.

8. After labeling the package must be sealed with evidence tape.

9. Residues must be store in airtight containers.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 8: Submission of Evidence and Chain of
Custody
 10. Druggist Fold is used to package small amounts of trace evidence

11. Glass Bottle with tight-fitting lid is used to place flammable liquids.

12. Screw Cap Jar or Vial is used to place liquids or solids.

13. The chain of custody documents the transfer of evidence/property from an

investigator to another individual, location or agency.

14. The Reason for the transfer as needed must be covered in chain of custody.

15. The chain of custody is initially established when an investigator takes custody of
evidence at a crime scene, or when evidence is received from an officer or
detective at, or from, the crime scene.

16. The notes must be taken including documenting the recovery location, the time
and date recovered or received, description of the item, condition of the item and
any unusual markings or alterations to the item.

17. A log must be maintained.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 8: Submission of Evidence and Chain of
Custody
 SUBJECT FORENSIC SCIENCE

Paper No. and Title PAPER No.7: Criminalistics and Forensic Physics

Module No. and Title MODULE No.9: Reconstruction of Crime Scene and
Problems encountered at the Scene of Crime

Module Tag FSC_P7_M9

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 9: Reconstruction of Crime Scene and
Problems encountered at the Scene of Crime
 TABLE OF CONTENTS

1. Learning Outcomes

2. Problems encountered at the crime scene

3. Crime Scene Reconstruction

3.1 Introduction

3.2 Importance of Crime Scene Reconstruction

3.3 Stages in Reconstruction

3.4 Types of Reconstruction

3.5 Do’s And Don’ts while writing a reconstruction report

4. Summary

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 9: Reconstruction of Crime Scene and
Problems encountered at the Scene of Crime
 1. Learning Outcomes

After studying this module, you shall be able to learn about-

 Problems encountered at the crime scene,

 Reconstruction of the Crime Scene,
 Importance of Crime Scene Reconstruction,
 Stages in Reconstruction,
 Types of Reconstruction, Do’s And Don’ts while writing a reconstruction report.

2. Problems encountered at the crime scene

The crime scene investigator works at the crime scene including collection of forensic
evidence. A crime scene investigator must be methodically complete in specific steps. They
are a number of problems which a crime scene investigator faces at the crime scene from
the time of arrival at the scene till the crime scene releases from the custody of police
officers. These problems make their job more difficult.

Education and training will reduce the mistakes made at the crime scenes. The best we can
do is to minimize the mistakes made at crime scenes through proper education and training.

The problems are as follows:-

1. Curious Onlookers

When you introduce humans you introduce human error!

Curious onlookers can cause major problems for crime scene investigators .Curious
onlookers can be an eyewitness, general public, friends and relatives of victim, media
people etc. These people can leave items at the crime scene which can interfere in his job.
At some crime scenes especially in case of high profile cases, curious onlookers become
unmanageable.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 9: Reconstruction of Crime Scene and
Problems encountered at the Scene of Crime
 It causes problems to the police force and crime scene investigator in recording of the crime
scene. Some specific areas need more presence of police so as to control the perimeter of
the scene of crime and also to allow the crime scene investigators to carry on with their
investigations safely and effectively. For the proper documentation and preservation of the
crime scene unnecessary access of public and police personnels should be avoided.
Locard’s Principle identified that when two objects come into contact there is an exchange
and they leave a trace of each other. The scene must be secured until the lead detectives and
crime scene experts attend and provide further directions. A defense often used in trials is
that the police contaminated or failed to control a crime scene and this situation can be
avoided if the investigators stick to protocols of preservation of scene of crime that includes
protective clothing to be worn by every staff member. A log has to be maintained such that
the access to the crime scene by the individual, his/her exit time and also the purpose of
entering the scene of crime is known. Challenge and refuse entry of any person who has no
genuine cause of entering including senior officers.

If the scene has been altered in any way, don’t try to recreate that scene. It should be noted
that a crime scene can never be reconstructed and any effort may result in significant
changes that might disturb the results of investigation. If the scene is recreated, then it
becomes perceived as a cover-up. If someone else sees you do it or helps you recreate it,
then it becomes perceived as a conspiracy.

2. Contamination

Crime Scenes are usually fragile. Anybody’s presence including the presence of police
investigators puts evidence in threat of being tainted or ruined. Till the completion of the
investigation only a minimal number of people should be allowed at the scene. Fingerprints
and other evidential items can be smeared and destroyed by careless investigators and other
technicians. A log must be maintained at the crime scene which keeps record of the each
investigator's presence, activities, and fingerprints so they will not be confused with other
evidence.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 9: Reconstruction of Crime Scene and
Problems encountered at the Scene of Crime
 As discussed initially the biggest problem encountered in crime scene investigations is too
many non-essential personnel in the scene. These personnel often contaminated the crime
scene. Unfortunately, the bulk of these non-essential personnel are often police officers.
Once the scene has been stabilized and the victim is either removed from the scene or
declared dead at the scene, then everyone, including police officers, must be removed from
the scene as soon as possible. The scene must be secured until the detectives and crime
scene investigators arrive. Until they arrive, no one, including sightseeing police officers
regardless of rank, should be allowed to go in the scene. Non-essential personnel will either
inadvertently disrupt some portion of the crime scene or they will give the impression that
something has been disrupted. One of the most popular lines used by defense attorneys and
the media during a trial is that the police contaminated, disrupted, tainted, or otherwise
screwed up the scene of crime. By eliminating the non-essential personnel in the scene and
controlling the scene once the situation is stable, then the police contamination statement
has no validity.

3. Accessibility

Hard-to-reach crime scenes can present a problem. Some crime scenes may be difficult to
reach due to weather factors, distance or due to many other reasons. The knowledge of the
distance of the crime scene must be given to crime scene investigator so that they can
prepare themselves with the appropriate equipment. In case the scene of crime is at some
rural place, the crime scene investigators must take into consideration that climatic changes
and animal activity can pose problems with the decomposition time and can also result in
variable changes in evidence.

4. Removal of Evidence

Sometimes the investigators at the scene of crime may not be able to respond in a timely
manner, and then the higher level police officers might give orders for removal of evidence
from the crime scene. This can present multiple problems for the technician, as the evidence
may not have been collected properly. Hence during the removal of evidence, the Police
investigators are needed to take photographs of evidences before it is moved and should talk
over with the investigators so as to determine the exact positioning of the evidence and
reasons pertaining to the removal of the evidence.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 9: Reconstruction of Crime Scene and
Problems encountered at the Scene of Crime
 5. Communication

Another major problem is the lack of communication at crime scenes. The first responding
officers must report everything they have observed including their actions at the scene, the
paramedics’ actions, the victim’s actions, the suspect’s actions, and any other actions taken
at the scene. This information must be communicated to the detectives and crime scene
investigators. The detectives and crime scene investigators must work and communicate
with the coroner’s or medical examiner’s investigators, so they can properly perform their
job when dealing with a deceased individual. While in return, the pathologist conducting the
autopsy should communicate the results of examination with the investigators of scene of
crime, the police officers and forensic scientists in the crime lab. The detectives and crime
scene investigators must also communicate with the forensic scientists so that the evidence
can be analyzed properly to obtain the maximum amount of information in the
investigation. The forensic scientist must give the results of the analyses to the detectives so
that the investigation can be completed. Finally, everyone involved in the case must have a
two way communication with the district attorney’s office. Lack of communication can
hamper the final disposition of a case.

6. Neglecting of the hidden and potential evidence

Another common problem encountered in crime scene investigations is that no one checks
the floor or the ground prior to entering the scene. Detectives and crime scene investigators
should examine the ground using oblique or side lighting so that shoeprints and other
evidence that end up on the ground can be more easily visualized and preserved. This
should be done even if a million people have been in the scene.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 9: Reconstruction of Crime Scene and
Problems encountered at the Scene of Crime
 3. Crime Scene Reconstruction

3.1 Introduction

Crime scene reconstruction is a process which determines or eliminates the events/ actions
occurred at the crime scene. The basis of the crime scene reconstruction is the location and
position of the physical evidence, the analysis of the crime scene pattern and the laboratory
examination of the physical evidence. Besides, scientific scene analysis, interpretation of
the scene pattern evidence and laboratory examination of physical evidence Reconstruction
also involves systematic study of related information and the logical formulation of a
theory.
Crime scene reconstruction is the forensic science discipline in which one gains "explicit
knowledge of the series of events that surround the commission of a crime using deductive
and inductive reasoning, physical evidence, scientific methods, and their interrelationships."

It can also be described as putting together a puzzle without knowing what the picture is
supposed to look like and without even having all of the pieces. The more pieces you have,
the more clearly you see the picture. It is the job of a crime scene Reconstructionist to find
the pieces and put them together.

The crime scene Reconstructionist seeks to determine:

 What happened?
 How did it happen?
 Where did it happen?
 Why did it happen?
 When did it happen?
 Who was involved?

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 9: Reconstruction of Crime Scene and
Problems encountered at the Scene of Crime
 3.2 Importance of Crime Scene Reconstruction

Reconstruction is partly based on the scientific experimentation and partly on past

experiences. Logic, careful observation, and considerable experience, both in crime scene
investigation and forensic examination of physical evidence, are necessary for proper
interpretation, analysis and crime scene reconstruction.

 Crime scene reconstruction is often useful to determine the actual course of a crime
by limiting the possibilities that resulted in the crime scene or the physical evidence
as encountered.

 The crime scene is also reconstructed to maintain the integrity of a crime scene.

 Reconstruction is based on the ability to make observations at the scene, the

scientific ability to examine physical evidence, and the use of logical approaches to
theory formulations.

Proper crime scene reconstruction is conducted in three phases:

1. Investigation: the crime scene is examined and documented to determine what

evidence is present without consideration to the particular meaning of any of the
evidence.
2. Analysis: individual items of evidence, or groups of related evidence, are examined
to determine their individual significance without respect to how those items fit into
the overall reconstruction of the crime.
3. Reconstruction: all evidence, including testimonial and documentary evidence, is
taken into consideration to determine how the crime took place. The overriding
concern here is: context.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 9: Reconstruction of Crime Scene and
Problems encountered at the Scene of Crime
 3.3 Stages in Reconstruction

Reconstruction is considered a scientific fact-gathering process and usually consists of

various actions that will help in reconstruction of crime scene. The following are the five
separate stages commonly used in the process of reconstruction:

1 -Data collection: All information or documentation information obtained at the crime

scene, from the victim, or witnesses. Data including condition of the evidence, obvious
patterns and impressions, condition of the victim, etc., are reviewed, organized, and studied.

2 -Conjecture: The sequence of events involved in the crime needs a possible elucidation
and conjecture before any comprehensive investigation of the evidence is done, but it must
not become the only explanation being considered at this stage. It is only a possibility.
There may be several more possible explanations, too.

3 -Hypothesis formulation: further accumulation of data is based on the examination of

the physical evidence and the continuing investigation. It also involves the examination of
the crime scene and assessment of the physical evidence. Scene and evidence examination
includes interpretation of bloodstain and impression patterns, gunshot patterns, fingerprint
evidence, and analysis of trace evidence. This process leads to the formulation of an
educated guess as to the probable course of events, a hypothesis.

4 -Testing: once a hypothesis is formulated, further testing must be done to confirm or

disprove the overall interpretation or specific aspects of the hypothesis. This stage includes
comparisons of samples collected at the scene with known standards and alibi samples,
chemical, microscopical and other analyses and testing. Controlled testing or
experimentation of possible physical activity must be done to collaborate the reconstruction
hypothesis.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 9: Reconstruction of Crime Scene and
Problems encountered at the Scene of Crime
 5 -Theory formation: additional information may be acquired during the investigation
about the condition of the victim or suspect, the activities of the individuals involved,
accuracy of witness accounts, and other information about the circumstances surrounding
the events. All the verifiable investigative information, physical evidence analysis and
interpretation, and experimental results must be considered in testing and attempting to
verify the hypothesis. When it has been thoroughly tested and verified by analysis, it can be
considered a plausible theory.

3.4 Types of Reconstruction

There are many types of reconstruction. It depends on the nature of the crime, the types of
events that have taken place, the questions needing to be answered and a reconstruction that
is based on the degree of involvement of the reconstructionist. Below is a general
classification of types of reconstruction in detail.

Classifications of Reconstruction Types

A. Specific type of incident reconstruction:

1. Accident reconstruction

 Other transportation accident reconstruction: trains, airplanes, boat accidents, etc.

 Industrial or construction accident reconstruction: ‘on the job’ or employee
accidents, building collapses, machinery, etc.
 Traffic accident reconstruction: automobiles, trucks, motorcycles, etc.

2. Specific crime reconstruction:

 Arson scene reconstruction

 White-collar crime reconstruction
 Homicide reconstruction
 Rape case reconstruction

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MODULE No. 9: Reconstruction of Crime Scene and
Problems encountered at the Scene of Crime
 B. Specific events reconstruction

 Sequence determination
 Directional determination
 Position determination
 Relational determination
 Conditional determination
 Identity determination

C. Degree of involvement reconstruction

 Total case reconstruction

 Partial case reconstruction
 Limited event reconstruction
 Specific pattern reconstruction

D. Specific type of physical evidence reconstruction

 Pattern evidence
 Shooting investigation evidence
 Serological evidence

3.5 Do’s And Don’ts while writing a reconstruction report

A reconstruction report must be:-

 Reviewed and signed by two examiners.

 State what materials were reviewed and used as a basis for the report.
 Accurate
 In agreement with notes taken during the review and reconstruction process.
 Do not interject or rely on un-validated information.
 Clearly state any relevant facts or circumstances not known to you.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 9: Reconstruction of Crime Scene and
Problems encountered at the Scene of Crime
 4. Summary

1. Curious onlookers, contamination, accessibility, removal of evidence,

communication and neglecting of the hidden and potential evidence are few
problems which an investigating officers encounters at the crime scene.

2. The crime scene reconstructionist seeks to determine what happened, how did it
happen, where did it happen, why did it happen, when did it happen, who was
involved and other relevant questions.

3. Proper crime scene reconstruction is conducted in three phases namely

Investigation, Analysis and Reconstruction.

4. The five separate stages commonly used in the process of reconstruction are Data
collection, Conjecture, Hypothesis formulation, Testing and Theory formation.

5. Accident reconstruction includes reconstruction of transportation accident, Industrial

or construction accident reconstruction & Traffic accident reconstruction.

6. Specific crime reconstruction includes reconstruction of Arson scene reconstruction,

White-collar crime reconstruction, Homicide reconstruction and Rape case
reconstruction.

7. Specific events reconstruction involves reconstruction of Sequence determination,

Directional determination, Position determination, Relational determination, and
Conditional determination and Identity determination.

8. Degree of involvement reconstruction includes Total case reconstruction, Partial

case reconstruction, Limited event reconstruction and Specific pattern
reconstruction.

9. Specific type of physical evidence reconstruction includes Pattern evidence,

shooting investigation evidence and Serological evidence.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 9: Reconstruction of Crime Scene and
Problems encountered at the Scene of Crime
 10. A reconstruction report must be Reviewed and signed by two examiners.

11. A reconstruction report must state what materials were reviewed and used as a basis
for the report.

12. A reconstruction report must be accurate.

13. A reconstruction report must be in agreement with notes taken during the review and
reconstruction process.

14. A reconstruction report does not interject or rely on un-validated information.

15. A reconstruction report should clearly state any relevant facts or circumstances not
known to you.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 9: Reconstruction of Crime Scene and
Problems encountered at the Scene of Crime
 SUBJECT FORENSIC SCIENCE

Paper No. and Title PAPER No.7: Criminalistics and Forensic Physics

Module No. and Title MODULE No.10: Forensic Physics: Instrumental

Techniques
Module Tag FSC_P7_M10

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 10: Forensic Physics: Instrumental
Techniques
 TABLE OF CONTENTS

1. Learning Outcomes
2. Introduction
3. Techniques - Brief Overview
4. Summary

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 10: Forensic Physics: Instrumental
Techniques
 1. Learning Outcomes

After studying this module, you shall be able to learn about various techniques used to
analyze evidence recovered from the crime scene.

2. Introduction

During the crime scene investigation, an investigating officer encounters with multiple
different types of evidences. The type of evidence recovered depends on the type of crime
scene. The evidence thus needs to analyze through various instrumental techniques.
Depending on the type of evidence recovered from the crime scene there are many
techniques which helps in analysis of evidence. Various methods are used for analysis
purpose.

3. Techniques- Brief Overview

The following is a brief description of few important techniques used to gather potential
information from the evidence and its application.

 Polygraph or Lie Detector

The polygraph is used for the purpose of lie detection. John Augustus Larson was the one
who invented polygraph in 1921. A polygraph measures and records several physiological
indices such as blood pressure, pulse, respiration, and skin conductivity while the subject is
asked and answers a series of questions. The analysis of polygram produced from
polygraph is based on the belief that deceptive answers will produce physiological
responses that can be differentiated from those associated with non-deceptive answers.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 10: Forensic Physics: Instrumental
Techniques
  Brain fingerprinting

Brain fingerprinting was invented by Lawrence Farwell. It is a technique that

uses electroencephalography also known as EEG so as conclude if any particular
information is stored in the brain of the individual by measuring electrical brainwaves and
further recording the response obtained from the P300 waves released from brain that is
also known as MERMER (Memory and Encoding Related Multifaceted
Electroencephalographic Response) in response to words, phrases, or pictures which are
shown on a computer screen.

 Narco- Analysis
The term ‘Narco-analysis’ was coined by Horseley, however this technique first reached
the mainstream in the year 1922 when Robert House, a Texas Obstetrician used the drug
scopolamine on two prisoners. In the Narco-analysis the hypnotic sedative preferably
Sodium Pentothal is administered intravenously into the subject. The dose which is to be
administered in the subject’s body is dependent on the age, sex, health, physical condition,
tolerance and idiosyncrasy of the subject. The rate of administration of the drug is so
adjusted such that the individual undergoing Narco-analysis is driven into state of hypnotic
trance thereby resulting in lack of inhibition. Although not impossible but it becomes
difficult in this state for the subject to lie or manipulate the answers. The subject is then
interrogated by the Psychiatrist/Forensic Psychologist in conjunction with investigating
agency. The revelation made during this stage are recorded, both in video and audio
cassettes followed by preparation of the report about the revelations, which will be
accompanied by the audio-video recordings. The personal consent of the subject along
with a court order is required for the conduction of the test.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 10: Forensic Physics: Instrumental
Techniques
  Microscopes

There are limitless applications of microscopy in the field of forensic sciences. The
microscope is used to form an enlarged image of a small object. After enlargement of the
image, the next concern is resolution (the ability to see increasingly fine details). For many
items, such as ink lines, bloodstains or bullets, no treatment is required. For examinations
of such kind of evidences, the evidence may be studied directly under the appropriate
microscope without any sample preparation.

Based on the investigation required different types of microscopes are available and used
for examination. The various microscopes are named as Stereomicroscope, compound
microscope, polarizing microscope, comparison, scanning electron microscope.

SEM provides superior result and hence used in many application area such as:-

 Gunshot residue analysis

 Investigation of gemstones and jewelry
 Firearms identification (bullet markings comparison)
 Filament bulb investigations at traffic accidents
 Handwriting and print examination / forgery
 Examination of paint particles and fibres
 Counterfeit bank notes
 Examination of non-conducting materials
 Trace comparison
 High resolution surface imaging

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 10: Forensic Physics: Instrumental
Techniques
  Abbe Refractometer

Abbe Refractometer is used to measure the refractive index of the given organic liquid. It
is a bench-top device for the high-precision measurement of an index of refraction.

 Voice Spectrograph

It can be defined as both auditory and spectrographic evaluation of one or more known
voices with an unknown voice for identification or elimination. The most important
parameter used in the determination of voice identification is the size of vocal cavities for
example, nasal, throat and oral cavity and also the length, shape and tension of the
individual's vocal cords located in the larynx. The second parameter is the manner by
which the articulators or muscles of speech are manipulated during speech. The samples of
voice recovered from the scene can provide valuable evidence after analysis from their
voice spectrograph.

 Docubox Dragon

Docubox Dragon allows comprehensive and systematic examination of documents in field

application. Extensive examination techniques with effective management and operative
accessibility achieve the growing needs for a fast and well-organized investigation of travel
documents, currency and security published documents, in the laboratory. The different
lighting conditions provide easy examination of document with differentiation of ink in a
convenient manner.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 10: Forensic Physics: Instrumental
Techniques
  Video spectral comparator

The VSC comprises of two components- a desktop computer that runs on software and an
imaging device that includes a colour charge coupled device (CCD) video camera, a black
and white CCD video camera, excitation/barrier filters, and various radiant energy sources
(tungsten, halogen, and fluorescent lamps). The instrument is equipped with the specialized
lighting tools for examination of documents. The visible, infrared, infrared luminescence,
ultraviolet, transmitted, coaxial and the oblique lighting conditions may be used alone or in
combination.

It permits the analysis and comparison of inks revealing alterations on a document as well as
whole questioned document without consuming much time.

Printing examination using Video Spectral Comparator

The VSC-5000 can be used to examine printed documents. The examination under different
lighting conditions can show that a document has been altered. Even without the source
printer, it may be possible to opine that two documents were both produced using the same
printer or not. Counterfeit pharmaceuticals, cigarettes, security documents etc. can be
examined by looking at the packaging.

By comparison of with genuine packaging it is possible to link counterfeit packaging

together by printing methods and defects. If the printers which have been used to produce
the packaging are found then it is possible to link the counterfeits to the printers.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 10: Forensic Physics: Instrumental
Techniques
  UV-Vis Spectrophotometer

Analysis of questioned documents involving forged bank cheques, altered documents, wills,
lottery tickets and counterfeit bank notes frequently include the ink examination to establish the
source of an ink used to print the fake document. Besides a large number of ink formulations,
UV fluorescing additives can be informative from the forensic point of view. The different
coloured inks such as black and blue ink may look same but there may be some important
differences in their chemical formulations.

The basic principle of UV-Visible absorption is that the molecules having the p-electrons / n-
electrons i.e. non-bonding electrons will absorb energy in the form of UV or visible light soa s to
stimulate electrons to the higher anti-bonding molecular orbital.

 Atomic Absorption Spectroscopy (AAS)

It is a spectro-analytical process for the measureable purpose of chemical elements using the
absorption of optical radiation (light) by free atoms in the gaseous state.

 Raman spectroscopy
It is a spectroscopic method based on inelastic scattering of one-color light, generally through a
laser source. It basically means that the occurrence of photons in one-color light deviates during
interaction with a sample. Raman effect is defined as the frequency range where the reemitted
photons are shifted up and down in comparison with the actual monochromatic frequency. The
shift in frequency gives information about vibrational, rotational and other low frequency
transitions in molecules. Raman spectroscopy can be used to study solid, liquid and gaseous
samples.

The technique is used to analyze different evidences such as drugs, inks etc.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 10: Forensic Physics: Instrumental
Techniques
  Fourier transform infrared spectroscopy

FTIR Spectrometry deals with the infra-red region of the electromagnetic spectrum that is light
with a longer wavelength and inferior frequency than visible light. The IR portion of the
electromagnetic spectrum is typically separated into 3 regions; the near-IR (14000– 4000 cm-1),
mid-IR (4000– 400 cm-1) and far- infrared (400– 10 cm-1). It is very useful for qualitative
analysis of compounds. IR Spectrometry is based upon the ability of certain substances to absorb
infrared radiation by interaction of an IR beam with a molecular bond of the sample. Absorption
occurs when the molecular bond has a vibrational frequency equal to the IR beam.

The technique allows analysis of all state of matter. Drug, Chemicals, Inks, Toners, etc. can be
analyzed using this techniques various biological & chemical evidences.

 Chromatography

Chromatography is the collective term for a set of laboratory techniques for the separation of
mixtures. The combination is mixed in a liquid known as the mobile phase, which transports it by
an arrangement carrying substance known as the stationary phase. The several components of the
mixture travel at various speeds, makes them to detach. The partition coefficient is depends on the
difference between the mobile and stationary phase.

 Thin layer Chromatography

Thin layer chromatography (TLC) is a broadly engaged laboratory method. IT involves a stationary
phase of a thin layer of adsorbent (silica gel, alumina, or cellulose) on a flat, inert substrate. It runs
swiftly, well partings, and the choice between dissimilar adsorbents. To achieve better resolution
and also for quantification purposes, high-performance TLC can be used.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 10: Forensic Physics: Instrumental
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  High Performance Thin layer chromatography

HPTLC also better known as high performance thin layer chromatography is the improved
method of thin layer chromatography (TLC). Various enhancements are possible to the general
or basic method of TLC so that the different steps can be automated, to increase the resolution
achieved and to allow more accurate quantitative measurements.

 High-performance liquid chromatography

High-performance liquid chromatography is a technique used to distinct, identify, and quantify

each component in a mixture. It depend on pumps to pass a pressed liquid solvent having the
sample combination by a column occupied with a solid adsorbent material.

 Gas chromatography-mass spectrometer

Gas Chromatography Mass Spectrometry (GC-MS) is a technique for the analysis and
quantitation of organic volatile and semi-volatile compounds. Gas chromatography (GC) is used
to distinct combinations into separate components by a temperature-controlled capillary column.

 Inductively coupled plasma-mass Spectroscopy

Inductively coupled plasma - mass spectrometry is the fastest rising trace component technique.
Since its commercialization in 1983, the technique has covered a wide range of application areas
including forensic, environmental, geochemical, semiconductor, clinical, nuclear, chemical,
metallurgical and many other scientific disciplines. The technique allows rapid sequential multi-
element determinations of nearly 70% of the elements in the periodic table with atomic mass
ranges 7 to 250 at the ultra-trace level. This encompasses Li to U. ICP- MS is the synergistic
combination of two well established techniques, namely, Inductively Coupled Plasma and Mass
Spectrometry.

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MODULE No. 10: Forensic Physics: Instrumental
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 The several elements of inkjet inks has trace impurities coming from several sources either
naturally present or due to adulteration. It is impracticable to remove then all together. Among
the impurities or contaminants there are several metals that are present in the inks at trace
levels. Depending on the place of manufacture, sources of raw materials, formulating
technology and contamination the trace metal profile would be a very good criterion on which
different inks could be characterized.

Nonetheless, the inorganic (elemental) constituents within gel inks can come from a wide range
of sources. The chief providers to the fundamental components of inks is the colorant (s) which
comprise the adding of any number of inorganic pigments (i.e. titanium dioxide, carbon black
in black inks, “metal powder ”, iron oxide, etc.) or organic pigments (which are not having
much inorganic elemental content) or a combination of both. Besides, the vehicle of the inkjet
inks (particularly which are water based solvents), the additives are another main basis for the
fundamental arrangement like pH regulating agents (i.e. sodium hydroxide, sodium carbonate),
surfactants (i.e. diphenyl oxide disulfonates, etc.). The inorganic trace element constituents
found in inkjet inks can virtually come from any of the manufacturing process and the stated raw
materials.

The technique can also be used to analyze various other evidences such as water.

 Differential Thermal Analysis (DTA)

It consists of measuring changes in heat content as function of difference of temperature between

the sample under investigation and a thermally inert reference compound as the two materials are
heated at elevated temperature or cooled to sub normal temperatures at predetermined rates. In
this manner enthalpy changes such as melting, vaporization, crystallographic phase transition or
chemical changes are detected from the endow and exothermic bands and peaks that appear on the
thermo grams,

The corresponding change in weight is determined by Thermo gravimetric analysis. Complete

thermo analytical data are obtained only by utilizing both methods of analysis. The information
obtained, coupled with X-Ray Diffraction, Optical and chemical analysis of the residues and any
involved gases provides a quantitative estimation of solid state reactions.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 10: Forensic Physics: Instrumental
Techniques
  Electrophoresis

Electrophoresis is the motion of dispersed particles relative to a fluid under the influence
of a spatially uniform electric field. Electrophoresis of positively charged particles
(cations) is known as cataphoresis, and electrophoresis of negatively charged particles
(anions) is called anaphoresis. Electrophoresis is a technique used in laboratories in order
to separate macromolecules based on size. This technique is used to analyze biological
evidences.

4. Summary

1. The polygraph is used for the purpose of lie detection and was invented by John
Augustus Larson in 1921.
2. Polygraph measures and records physiological indices such as blood
pressure, pulse, respiration, and skin conductivity while the subject is asked and
answers a series of questions.
3. Brain fingerprinting is a technique that uses EEG to determine whether specific
information is stored in a subject's brain by measuring electrical brainwaves and
recording a brain response known as a P300-MERMER.
4. Brain fingerprinting was invented by Lawrence Farwell.
5. MERMER stands for Memory and Encoding Related Multifaceted
Electroencephalographic Response.
6. In the Narco- Analysis the hypnotic sedative (Sodium Pentothal) is administered
intravenously into the subject.
7. The dose of hypnotic sedative which is administered in the Narco Analysis is
dependent on the age, sex, health, physical condition, tolerance and idiosyncrasy of
the subject.
8. Various type of microscope such as Stereomicroscope, compound microscope,
polarizing microscope, comparison, scanning electron microscope is used for
forensic analysis of sample.

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MODULE No. 10: Forensic Physics: Instrumental
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 9. A scanning electron microscopy is used in many application area such as Gunshot
residue analysis, Investigation of gemstones and jewelry, Firearms identification,
Filament bulb investigations at traffic accidents, Handwriting and print examination /
forgery, Examination of paint particles and fibres, Counterfeit bank notes,
Examination of non-conducting materials, Trace comparison, High resolution surface
imaging.
10. Abbe Refractometer is used to measure the refractive index of the given organic
liquid.
11. Docubox Dragon and video spectral comparator allows comprehensive and
systematic examination of documents in lighting conditions provides easy
examination of document with differentiation of ink in a convenient manner.
12. The technique allows analysis of all state of matter. Drug, Chemicals, Inks, Toners
etc. can be analyzed using this techniques various biological & chemical evidences.
13. Inductively coupled plasma - mass spectrometry (ICP-MS) is the technique for the
detection of trace
14. ICP-MS allows multi-element determinations of the elements (from Li to U) at the
ultra-trace level.
15. Encase is used to recover deleted data from storage devices such as compact disks,
hard disks, floppy disks, etc.
16. Electrophoresis is defined as the process wherein the dispersed particles are in
motion relative to the specific fluid under the influence of an electric field which is
uniform and used to analyze biological evidences.
17. Chromatography is a technique used for the separation of mixtures.
18. The various chromatographic techniques are used to analyze evidence recovered
from the crime scene are Thin layer Chromatography, High Performance Thin layer
chromatography, High-performance liquid chromatography, Gas chromatography-
mass spectrometry etc.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No. 10: Forensic Physics: Instrumental
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SUBJECT FORENSIC SCIENCE

Paper No and Title Paper 7 : Criminalistics and Forensic Physics

Module No. and Title Module No. 11; Trace evidence

Module Tag FSC_P7_M11

TABLE OF CONTENTS

1. Learning Outcomes
2. Introduction
3. Trace Evidence
4. Collection of Trace Evidence
5. Preservation of the evidence
6. Problems while collecting Trace Evidence
7. Summary

Forensic Science PAPER No. 7: CRIMINALISTICS AND FORENSIC PHYSICS

MODULE No. 11; TRACE EVIDENCE
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Ridge Characteristic

1. Learning Outcomes
After studying this module, you shall be know about

· The importance of the trace evidence

· Various methods for collecting and preserving the trace evidence
· Problems faced while collecting trace evidences

2. Introduction
The importance of the trace evidence in the field of criminal investigations came into picture in
the early twentieth century. Since then these have been used to reconstruct the crimes so that a
clear description of the people, places and the things involved in the crime becomes available.
Such evidence include finger prints, fibres, paints, glass, gunshot residue etc to follow the
criminals but these evidences have to be collected with a special care so that they are not
destroyed and proper analysis can be done. The carelessness while collecting the evidence may
lead to contamination and incorrect results. It is actually a physical contact between the criminal
and the victim that results in the transfer of trace materials. Their identification and comparison
associates the suspect to the crime scene under investigation.

3. Trace Evidence
Trace Evidence refers to small samples of a substance, in particular, finger prints, fibres, hairs,
glass fragments, soils, gunshot residue, paint chips etc. Dr. Edmond Locard, founder of the
Institute of Criminalistics at the University of Lyon, France, showed their importance for the first
time. He gave the famous Principle known as Locard’s Exchange Principle, which states that
every contact leaves a trace which means that the criminal will definitely leave a trace evidence
at the crime scene. Most of the crime scenes do contain trace evidence left behind by the criminal
unconsciously. These evidence serve many roles during an investigation like identifying the
remains at the crime scene or reconstruct a crime. The presence of trace evidence is mainly
dependent on the type of material to be considered as a trace evidence since some particles and
substances remain on a surface for a longer time. This depends on the size, shape and the amount
of the particles deposited. Smaller particles persist for a longer time in comparison to the larger
particles. Also irregular surfaces such as wood collect smaller particles more readily than the
smooth surfaces.

Among the important examples of the trace material we have:

Hairs (Human and animal hair): The examinations of the hairs determine whether the hair is
human or animal. In case it is human hair one can determine the racial characteristics like body
area, length, root type or any artificial treatment done on the hairs. If, the hair is of any animal
species, then the species and breed of the animal can be determined.

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Fig1: Some hair samples

Fibres: The fibre examination can determine whether the fibre is natural or man-made. Its source
can be determined by comparing it with fibres from a known source. Natural fibres are mainly
from a plant or an animal source like cotton, silk etc. These can be detected easily by microscopy.
But most of the fibres used in the garments now a days are synthetic. Standard samples are taken
for comparison with suspect samples.

Fig 2: Natural and man-made Fibres

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Fabric: Fabric examinations determine whether the suspect fabric and a known piece of fabric are
same in construction, color and composition.

Feathers: Feather examination can determine the species of the bird after comparing with the
known samples

Glass: Since different types of glasses are produced in different ways, it is possible to determine
the source from which the broken piece of glass used as the evidence, originated. One can easily
come to the conclusion whether the glass under consideration is a window glass, in car
windshields, or a vehicle’s rear and side window glass.

Fig 3: Analysis of a glass sample

Paint: The analysis of the paint can be mechanical, physical and chemical. The analysis includes
matching of flakes of paint, the exact composition of the paint, the texture, appearance, thickness
and the pattern of the occurrence.

Fig 4:Comparison of Paint Flakes

Finger prints: Fingerprints are actually the best evidence as fingerprints can identify the
person exactly, present at the crime scene.

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Fig 5: Fingerprints

Blood samples: The shape of the blood samples can actually tell as from what height they
have fallen down. DNA from blood samples can be extracted to simplify the identification
from crime scene.

Fig 6: Blood Sample

4. Collection of Trace Evidence

After the location of the evidence from the crime scene is noted, the collection process for the
evidence begins. There are two important precautions to be taken into account while collecting
the evidence:

The samples of trace materials like hairs to be tested should be carefully collected and along with
this , the carrier on which the material is found like the bedding, clothing, should also be
collected.

Forensic Science PAPER No. 7: CRIMINALISTICS AND FORENSIC PHYSICS

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Before collecting the evidence, several methods are employed to detect the evidence that include
visual searches by oblique lighting, Ultraviolet light sources, lasers etc and by magnification.
While collecting the items, one must be careful to prevent contamination and loss of the evidence.
For that purpose, the contact between the item to be collected, as trace evidence and other people
should be avoided and the investigating team should be in appropriate apparels.

First, the most fragile and the evidence that will easily get destroyed are collected. Then those
evidence are collected that need to be moved. The methods used for collecting should direct and
simple. The methods usually depend on the type of the evidence to be collected and also on the
place or the carrier the trace is to be collected from.

The tools used for the collection include :

Knife, tweezers, plastic containers with lids, scalapel, scissors, comb, filtered vacuum devices,
ultraviolet light etc.

The following techniques are used for collecting the evidence:

· Picking: The evidence is separated from an item using clean forceps, tweezers,
scalapel,knife etc.

· Lifting: An adhesive such as a tape is patted or rolled on the item causing the trace
material to stick to the tape without overloading it. The collected material is lifted and
placed on either a transparent plastic sheet, a glass slide or glass petri dishes as it protects
the sample from getting contaminated and can be easily removed for comparisons. But,
these adhesive materials should be maintained so as to avoid any contamination.

· Scraping: Tools like a clean spatula are used to remove the trace material from an item
to a clean paper which is immediately sealed to avoid sample loss. This is usually
conducted in the laboratory to avoid the risk of contamination.

· Vacuum Sweeping: A vacuum cleaner with a filter trap is used to collect evidence from
the crime scene. The filter along with its contents are immediately packed to avoid losses.
The filter, vacuum parts should be cleaned thoroughly for other investigations. Such
technique results in the collection of large amount of evidence.

· Combing: A clean comb or brush is used to collect evidence from hairs and fibres of the
individual. The comb as well as the material collected should be packed together.

· Clipping: Nail clipping is used to recover the trace evidence from fingernails. The
fingernails are clipped using clean scissors or clippers and then packed in clean paper.
Fingernails can also be scrapped for obtaining the evidence from under the fingernails
.
· Solvent extraction: In certain cases that involve grease or oil, a solvent extraction is used
to collect the evidence.

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Fig 7: Methods for collecting the evidence

5. Preservation and packaging of the evidence and its carrier

The preservation and packaging of the trace evidence and the carriers varies from material to
material.

· The most important step among the preservation of the evidence is to take a photograph
of all the trace evidence from criminal investigation sites, while still in the place.

· All evidence packages should be sealed properly so that the samples are not tampered,
contaminated or harmed, as might be the case if left open.

· Very small and loose trace materials should be kept in unused containers like paper
packets or petri dishes, which are further secured in a paper bag.

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· Large items or the carriers like the clothing; bedding etc. should be kept separately in
unused packaging material.

· If the clothing or the bedding is wet, then it should be dried quickly without exposure to
either heat or sunlight. This is done in a secured area so that no evidence is either lost or
gets contaminated. Also, an arrangement for collecting any trace evidence that falls from
the carrier while drying is also made during the procedure.

· Certain manageable carriers or items at the crime scene that have got quite visible and
firm trace evidence are documented, packaged and are transported to the laboratory.

· If there are items or the carrier at the crime scene that bear trace materials which can be
easily lost or the carrier itself cannot be transported, then they are documented are
collected by an appropriate method.

Fig 8: Preservation of the evidence

Some examples for collection and preservance of evidence:

· If there is gunshot residue on the clothing of the victim, then it is collected in a sealed
paper bag to avoid contamination with the presence of other materials.

· If illicit drugs are there, then they are collected with a knife and each of the drugs is
sealed in a separate, sterile container. The beddings, clothing’s, towels etc are taken and
packed separately.

· Body fluids like semen, saliva, vomit etc are collected with tweezers, scalpel, sterile cloth
squares, ultraviolet light while blood samples are collected by blood collection kit.

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· If there are hairs and fibres available as trace materials on the crime scene, then they are
collected using comb, tweezers and filtered vacuum device and then sealed in paper
packets.

The trace evidence remains in a secured area where a control on the access to the area is
maintained to protect it from loss, damage or contamination. It is documented and kept in custody
till its submission into the court. The security is the responsibility of all the persons involved in
collecting, packaging, sealing, transporting and preserving the evidence.

6.Problems that occur while collecting the evidence

· Mishandling of the evidence or presence of certain near by objects can contaminate the
evidence like mixing of blood of the suspect and the victim.

· Fingerprints and DNA traces are much more vulnerable to what we call as false positives.
By false positive we mean a type of error, which occurs when, an analysis gives positive
result or incorrect result which should not have given. These mostly occur in drug
analysis, detection and analysis of bloodstains.

7. Summary
§ The trace evidences are the minute samples of substances like hairs, fibres etc which give
a complete description of the people and the places involved in the crime.
§ Dr. Edmond Locard, gave the famous Principle known as Locard’s Exchange Principle,
which states that every contact leaves a trace.
§ The nature of the trace evidence is quite variable and is found almost at all the crime
scenes.
§ Usually, in forensic physics laboratories, the analysis of both microscopic as well as
macroscopic trace evidence is done.
§ These evidences have to be then protected and packaged carefully lest they get
contaminated or destroyed before their submission to the court.
§ The most important step among the preservation of the evidence is to take a photograph
of all the trace evidence from criminal investigation sites, while still in the place.

Forensic Science PAPER No. 7: CRIMINALISTICS AND FORENSIC PHYSICS

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Subject Forensic Science

Paper No and Title Paper 7 : Criminalistics and Forensic Physics

TOPIC Tool Marks

Module No. FSC_P7_M12

Forensic Science PAPER No. 7: CRIMINALISTICS AND FORENSIC PHYSICS

Module No 12: TOOL MARKS
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TABLE OF CONTENTS

1. Learning Outcomes

2. Introduction

3. Tool marks - definition

4. Characteristics of tool marks

5.Types of tool marks

6. Tools that can be used as evidence

7. Surfaces where tool marks can be found during investigation

8. Examination and matching of tool marks

9. Summary

Forensic Science PAPER No. 7: CRIMINALISTICS AND FORENSIC PHYSICS

Module No 12: TOOL MARKS
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Ridge Characteristic

1. Learning Outcomes
In this module, you shall be able to learn about

· The tools marks and their characteristics

· Types of tool marks
· Matching of tool marks

2. Introduction
Tool marks are the impressions left by a tool on coming in contact with a surface. These tool
marks show different types of characteristics depending on the type of impression, its shape and
how the mark was created. Depending upon the force with which the marks have been put, the
tool marks are divided into different categories. The examination of tool marks is an important
factor in the field of criminalistics as it can directly establish the link between a tool mark and the
tool that created it. These impressions also help to reconstruct the crime scene.

3. Tool marks - Definition

A tool is a hard object which when forcefully comes into contact with another object, leaves a
mark on the softer one like a screw driver, plier or an arcjoint plier , hammer and wire cutters etc.

A tool mark is defined as an impression left by a tool when it comes into contact with a surface. If
the tool contacts the surface with a large force, it leaves behind an indentation and the pattern of
the tool is permanently reproduced on the surface. These marks play a very vital role in forensic
science as the criminals have a tendency to use tools for committing burglaries or other heinous
crimes such as cold blooded murders. For example, if a burglar tries to enter a house by breaking
the lock with the help of a screw driver, the marks left by the tool are a direct evidence of the
presence of that tool at the crime scene. But, if the tool is found with a suspect or even near the
suspect, it provides a direct link between the suspect and the crime scene.
In the field of forensic science, the tool marks can either take the form of negative impressions or
an abrasion or both.

Fig 1. Tool and tool marks

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4. Characteristics of tool marks

Tool marks have two different kinds of characteristics:

Class and Individual

· Class characteristics:

These types of characteristics of a tool mark include the type of impression, its general
shape and dimensions. These characteristics are typically the broad characteristics from
which the crime investigator can determine what type of tool created the impression and
how was it created. But, this does not serve the purpose of the identification of the exact
tool that actually created the mark. Thus, if only the class characteristics would have been
available, then it would not have been possible to distinguish which tool among a pack of
similar tools made an impression. For this, individual characteristics are taken into
consideration.

· Individual characteristics:

Individual characteristics are microscopic characteristics, which refer to the small,

peculiar features exhibited by the tool that are individual to one particular tool. These
characteristics include small, microscopic ridges and irregularities present on the tool
itself. For example, the tip of a screw driver is never exactly flat but has irregularities
near its edge. These characteristics are created by the use and misuse of the tool, its
cleaning and maintenance. These characteristics actually permit a formal identification. If
such characteristics are available on a tool mark, then it is possible to identify the tool
that was used in committing the crime, even among a series of identical tools.

5. Types of tool marks

Depending on the force with which a tool comes in contact with a softer surface,
Tool marks are divided into two different categories.

· Impressed tool marks:

These marks occur when the surface onto which the tool comes in contact with, is softer
in comparison. When the tool comes in contact with the object (softer than the tool) with
a huge force in a motion perpendicular to the plane of the surface leaving an impression
on the surface, such tool marks are called impressed tool marks. There is no lateral
motion. At the crime scene, the unique imperfections of the tools are transferred to the
surface that make possible a positive identification of the tool involved in the crime.
As an example, when a tool like a screw driver is used by the criminal to forcefully intend
a metal surface without penetrating, then the impressions it leave will be helpful in
identifying the tool.

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Fig2. Tool marks by an arc joint plier

(Impressed tool marks)

· Striated Tool marks:

These marks are produced when the tool contacts an object with lateral or sideways force.
In such a case, the tool is placed against an object and is moved parallel to the object or
across the object.

Fig 3: striated marks

Some tool marks can be a combination of the above two types.

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6. Examples of types of evidence submitted in tool marks case:

Types of evidence submitted in tool marks cases include tools like

· Bolt cutters
· Screwdrivers and chisels
· Scissors
· Knives and box cutters
· Pliers and wrenches
· Crowbars tire irons
· Saws and hammers

Fig 4: Different types of tools

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7. Examples of places and surfaces where tool marks can be observed

during investigation:
Some of the places and surfaces where tool marks are likely to be found during investigation
are:

· Wire, chains
· Door and window frames
· Sections of metal sheets
· Safes
· Human bone or a cartilage
· Padlocks and door knobs
· Bolts and locks etc.

Fig 5: Different types of surfaces where tool marks can be found

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8. Examination and matching of tool marks:

Examination and comparison of the tool marks from a crime scene with the tool marks of the
actual suspect tool can act as an important ad invaluable evidence in linking the suspect to a
particular crime and thus the case can be concluded.

The major precautions that are to be taken while examining the tool marks:

· Door and windows and other openings with handles or locks at the crime scene should
not be touched if they are broken or the locks are cut, lest the tool marks or the finger
prints are destroyed.
· A tool should not be fitted forcibly into the impression which may affect the laboratory
analysis.
· The tool marks should be documented completely including sketches and photographs
before removing.
· If any trace evidence is found on the tool marks, the examination of the trace evidence
should be done prior to tool marks examination.
· Tool marks evidence should be packaged so that it is not damaged as it may change the
microscopic characteristics.
· If the tools are stained with blood or some other biological material, then that has to be
cleaned using a soft bristle brush and disinfectants like Terg-A-Zyme, ethanol etc.
· The tools are always cleaned with a cotton tipped swabs saturated with ethanol or
acetone.

The tool mark examination and matching consists of different phases:

· The first step is to observe some physical features of the tool :

Ø Manufacturer
Ø Type of tool
Ø Composition and color
Ø Condition of tool’s finish
Ø Dimensions of the tool (overall length, width etc)
Ø Any irregularity at the ends of the tool

· The next step is to observe the physical features of the tool marks:

Ø The type of the tool mark

Ø Width or diameter of the tool mark
Ø Type of cutting motion by the tool
Ø Direction of motion of the tool that created the tool mark
Ø Position of the tool mark on the tool

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Fig 6: Examination of tool marks in the laboratory

· A photograph of the impression made by the tool is taken which provides a permanent
record of some of the characteristics of the tool mark.

· If the carrier or the object where the tool mark is located, cannot be collected as an
evidence then a cast of the tool mark is made with a dental paste.

· After discovering the tool, if its class characteristics match with those exhibited by the
tool mark under consideration, then the comparison process is started.

· The tool is observed and a photograph is taken and then the comparison tool marks are
made of a softer surface.

· The comparison is then done between the comparison tool marks and the tool marks
under investigation using a comparison microscope which consists of two microscopes
connected with each other with which two objects can be viewed simultaneously with the
same degree of magnification or a stereomicroscope.

· If a match exists then the common origin between the two tool marks is established
which then leads to a conclusive report of the case.

Forensic Science PAPER No. 7: CRIMINALISTICS AND FORENSIC PHYSICS

Module No 12: TOOL MARKS
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Fig 7: comparison microscope Fig 8: Stereomicroscope

Fig 9: comparison process in the laboratory

9. Summary
To summarize, the tool marks which are the impressions left by a tool at the crime scene play a
vital role in discovering and identifying the tool used to commit the crime by comparison
processes. These tool marks have to documented carefully and completely including the physical
features of the tool and tool marks, lest some information is destroyed. The tools under
examination should also be cleaned with soft cloth dipped in ethanol. The examination process is
carried by comparison microscope and stereomicroscope.

Forensic Science PAPER No. 7: CRIMINALISTICS AND FORENSIC PHYSICS

Module No 12: TOOL MARKS
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Forensic Science PAPER No. 7: CRIMINALISTICS AND FORENSIC PHYSICS

Module No 12: TOOL MARKS
____________________________________________________________________________________________________

Subject Forensic Science

Paper No and Title Paper 7 : Criminalistics and Forensic Physics

TOPIC Ingredients of glass

Module No. FSC_P7_M13

Forensic Science PAPER No. 7: CRIMINALISTICS AND FORENSIC PHYSICS

Module No 13: Ingredients of GLASS
____________________________________________________________________________________________________

TABLE OF CONTENTS

1. Learning Outcomes

2. Introduction

3. Glass – Definition

4. Ingredients for making glass.

5. Types of glasses

6. Summary

Forensic Science PAPER No. 7: CRIMINALISTICS AND FORENSIC PHYSICS

Module No 13: Ingredients of GLASS
____________________________________________________________________________________________________

Ridge Characteristic

1. Learning Outcomes
In this module, you shall be able to learn about

· Composition of glass and

· Types of glasses

2. Introduction
The knowledge about the glass and its composition plays a very important role in the field of
Forensic Science. It makes the examination of the glass that has broken or being used for
committing the crime easier for the investigation team. The material of the glass reveals its make
and helps reaching the suspect. Silica is the main ingredient used in glass making along with
other minor ingredients like metal oxides and color additives. Depending upon the composition
and the minor ingredients, there are different types of glasses like lead glass, soda lime glass,
aluminosilicate glass, borosilicate glass etc.

3. Glass - Definition
Glass is defined as an amorphous, hard, brittle substance which is usually transparent but
translucent and also opaque at times. It is formed by the fusion of one or more oxides like that of
silica, boric oxide, phosphoric oxide and some metallic oxides followed by rapid cooling of the
fused material to prevent crystallization of the components involved.

In other words, glass can be considered as a super cooled liquid of extremely high viscosity.

4.Ingredients for making glass:

The following are some ingredients used in the manufacture of glass along with some additives
required for specific properties.

1.Sand or silica:

Silica is the main ingredient for glass making, with a very high melting point of around 2000
degree C. This is the major reason why it is possible to make products like halogen lamps from
just silica itself. Its mainly obtained from the pure sands of Parengarenga Harbour of North Cape.
It is washed and sifted to remove shells, stones before mixing.

Forensic Science PAPER No. 7: CRIMINALISTICS AND FORENSIC PHYSICS

Module No 13: Ingredients of GLASS
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Fig 1. Silica SiO2

2.Sodium Carbonate (or Soda Ash) :

Sodium Carbonate is added to make the process of glass manufacturing more efficient as it
reduces the melting point of silica to around 1000 deg C. It was earlier found in the ash of some
plants but is now produced from the table salt itself. But, the sodium carbonate tends to make the
finished glass water soluble which is not desirable in glass making. Its main source is from USA.

Fig 2. Soda Ash (Na2CO3)

3.Lime or calcium oxide:

Calcium oxide is extracted from limestone. It is added to counter the effect of sodium carbonate
and makes the glass non soluble in water. Its main source is Waitomo.

Forensic Science PAPER No. 7: CRIMINALISTICS AND FORENSIC PHYSICS

Module No 13: Ingredients of GLASS
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Fig 3. Lime stone (CaCO3)

4.Metallic Oxides:

Aluminium oxide and magnesium oxide are added to further enhance the properties of glass.

5.Other Additives:

A number of different other ingredients are added in order to change the properties of the finished
glass as per the requirement.

Some examples are:

· Lead: Lead is added to make crystal glasses. Because of its good reflective properties,
the glass thus formed appears to sparkle, which is used for forming decorative patterns on
the ordinary glass.

· Boron: The addition of boron changes the thermal and electrical properties of the glass
and is thus, used to make Pyrex glassware that can withstand extreme temperatures.

· Lanthium Oxide: With its excellent light reflective properties, it is used to make high
quality lenses in glasses. Earlier Thorium Oxide was used, but due to its radioactive
properties, it is no longer used.

· Iron: It is used to absorb infrared energy in the heat absorbing filters installed in the
movie projectors.

Forensic Science PAPER No. 7: CRIMINALISTICS AND FORENSIC PHYSICS

Module No 13: Ingredients of GLASS
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6.Colour Additives:

Colour to the glass can be done either by glass oxidation or by introducing a large variety of
additives . It is actually difficult to make a clear glass. Metals and oxides are also used to give
colour to glass.

Glass oxidation is promoted by the addition of carbon while the degree of oxidation is measured
on an arbitrary scale known as carbon number.
For example:

Clear glass has C no : 0

Dark green glass has C no : -28

Various additives and the colors they give :

Iron oxide: Blue green

Iron oxide and Chromium: Richer green
Sulphur, Carbon and iron salts: amber, yellow
Manganese: purple
Selenium: Red or pink
Cobalt: Blue
Tin oxide, antimony and arsenic: White opaque
Copper oxide: Turquoise
Nickel: blue
Etc.

Some pictures of coloured glasses:

Cobalt glass

Forensic Science PAPER No. 7: CRIMINALISTICS AND FORENSIC PHYSICS

Module No 13: Ingredients of GLASS
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Cranberry glass

5.Types of glasses:

Depending upon the chemical composition , all commercial glasses are divided into six basic
categories:

· Soda lime Glass:

It is the most common and cheapest form of glass. It is used for manufacturing window
glass, bottles, containers, light bulbs, bangles, ophthalmic lenses, car head lamp etc. The
common oxides found are Na, Ca, Mg, Al.
It is not highly resistant to high temperature and sudden changes of temperature while the
resistance to corrosive chemicals is fair

The composition is as follows:

Silica : 60% - 70%
Soda : 12% - 18%
Lime : 5% - 10%

Forensic Science PAPER No. 7: CRIMINALISTICS AND FORENSIC PHYSICS

Module No 13: Ingredients of GLASS
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· Lead Glass:

This type of glass has fairly high percentage of lead oxide. It is quite soft and because of
its high refractive index, it gives brilliance to the glass. As a result, it is used to make
decorative glassware, neon sign tubes, thermometer tubes, for the absorption of X-rays
and other radiations. Its excellent electrical insulating property makes it favorable for
electrical applications. This glass is more expensive than soda lime. It cannot withstand
high temperature and sudden temperature changes as has got low melting point.

The composition is as follows:

Silica : 54% - 65%
Lead Oxide : 18% - 38%
Soda/Potash : 13% - 15%

· Borosilicate glass:

This type of glass has got substantial amount of Boric Oxide which makes it resistant to
heat, acid corrosion and alkalis. They are not as easily fabricated as soda lime or lead
glass and are hard as they have lower coefficient of expansion, hence can be used at high
temperature. These glasses are used for making laboratory glassware, domestic oven
ware, in industry for gauge glasses, pipelines, photochromic glasses, sealed beam
headlights etc.

The composition is as follows:

Silica : 70% - 80%
Boric oxide : 7% - 13%
Alkali : 4% - 8%
Aluminum Oxide : 2% - 7%

Forensic Science PAPER No. 7: CRIMINALISTICS AND FORENSIC PHYSICS

Module No 13: Ingredients of GLASS
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· Aluminosilicate glass:

This type of glass has got aluminum oxide added to it. Although it is similar to
borosilicate glass but is more hard to fabricate and has got greater chemical durability. It
can withstand very high temperature as its melting point is almost 1000 deg C.It can be
used as resistors for electronic circuits.

The composition is as follows:

Silica : 67%
Aluminum oxide : 17%
Calcium oxide : 8%
Magnesium oxide : 7%

· Ninety six percent silica glass:

It is a type of borosilicate glass from which all the non silicate elements have been
removed. This glass is resistant to temperature up to 900 deg C.

Forensic Science PAPER No. 7: CRIMINALISTICS AND FORENSIC PHYSICS

Module No 13: Ingredients of GLASS
____________________________________________________________________________________________________

· Fused silica glass :

It is a glass which is pure silicon dioxide in a non-crystalline state. It is very difficult to

fabricate and is the most expensive of all types. It can sustain temperatures up to 1200
deg C.

6.Summary
To summarize, we have studied glass and the various ingredients involved in the making of glass
and how color is given to the clear glass. This is important in recognizing the glass sample
involved in the crime. The material of the glass reveals its make and helps in reaching the suspect
and hence, solving the crime partially. Depending upon its composition, different types of glasses
exist.

Forensic Science PAPER No. 7: CRIMINALISTICS AND FORENSIC PHYSICS

Module No 13: Ingredients of GLASS
____________________________________________________________________________________________________

Subject Forensic Science

Paper No and Title Paper 7 : Criminalistics and Forensic Physics

TOPIC Manufacture of glass – part 1

Sub-Topic (if any)

Module No. FS/P7/M14/manufacture of glasses

Forensic Science PAPER: CRIMINALISTICS AND FORENSIC PHYSICS

TOPIC: MANUFACTURE OF GLASS PART 1
____________________________________________________________________________________________________

TABLE OF CONTENTS

1. Learning Outcomes

2. Introduction

3. The Float Glass Process

4. Summary

Forensic Science PAPER: CRIMINALISTICS AND FORENSIC PHYSICS

TOPIC: MANUFACTURE OF GLASS PART 1
____________________________________________________________________________________________________

Ridge Characteristic

1. Learning Outcomes
In this module for manufacture of glass part 1, you shall be able to learn about one of the two
processes of manufacture of glass namely

· The Float Glass process

2. Introduction
The manufacture of glass involves the mixing of silica, soda ash, sand, lime and salt etc and
other oxides that further enhance the properties of glass. The glass production involves two
methods: the float glass process for producing sheet glass and glass blowing for producing glass
bottles and other containers.

The manufacture of glass is achieved by a continuous process using almost 500m long furnace.
The furnace is operated continuously with raw materials charged from one end while molten glass
being drawn from the other end.

3. The Float Glass Method

The Float glass is just a sheet of glass which is made by floating molten glass on a bed of molten
metal. Modern windows are made from float glass. Most float glass is soda lime glass.

Sir Alastair Pilkington was the first person to develop the process of float glass.

Fig 1: Crystal palace in London made of float glass

Forensic Science PAPER: CRIMINALISTICS AND FORENSIC PHYSICS

TOPIC: MANUFACTURE OF GLASS PART 1
____________________________________________________________________________________________________

Fig 2: Window glass made from float glass

The major stages involved in this method are as follows :

Fig 3: Block diagram along with the pictures for the float glass process

Forensic Science PAPER: CRIMINALISTICS AND FORENSIC PHYSICS

TOPIC: MANUFACTURE OF GLASS PART 1
____________________________________________________________________________________________________

· Mixing of raw materials – batch :

The ingredients used for making glass are stored properly to maintain high standards of
consistency of composition and freedom from impurities. The raw materials are weighed
properly and mixed thoroughly before being put into the furnace. All the major ingredients
like soda ash, silica etc and minor additives present in the charge or batch are delivered to the
furnace. Cullet or waste glass is also an important raw material that assists the melting
process.

· Glass melting:

The raw materials - both batch and cullet are heated in a furnace to about 1500 deg C. The
furnace is constructed of refractory blocks which can withstand the temperatures greater than
1500 deg C and the corrosive nature of molten glass. The greatest percentage of glass is melted in
tank furnaces to produce a continuous flow of glass to be fed to the automatic glass forming
machine.

Fig 4: Batch feed of a glass furnace

· Refining and homogenizing:

While the raw materials are melting in the furnace, gases like carbon dioxide are emitted and
they react. The molten glass must be held at a temperature which is high enough to permit all
the glass bubbles to rise to the surface and hence eliminated. This elimination takes place in
the refining stage as the molten glass passes through the furnace. When the glass is
sufficiently refined and homogenized by removing the bubbles and impurities, the
temperature of the molten glass is reduced to 1100 deg C as it passes down the furnace
towards the forming stages. This process is important for producing high quality glasses and
can last up to 50 hours. Glass has no fixed melting or freezing point but it changes gradually
from a viscous liquid to a rigid solid as its viscosity increases on cooling.

Forensic Science PAPER: CRIMINALISTICS AND FORENSIC PHYSICS

TOPIC: MANUFACTURE OF GLASS PART 1
____________________________________________________________________________________________________

· Glass forming/the float bath:

The molten glass from the furnace flows on to molten metal like tin and form a ribbon about
6.8mm thick. It flows over molten tin and is cooled to 600 deg C when it leaves. Thicker glass up
to 25mm thick can be further produced by not allowing to settle at 6.8mm. The ribbon is thus
stretched to produce thinner glass. In other words, it is the gradual and continuous change in
viscosity with temperature which permits molten glass to be converted into large number of
products. Thus, in an appropriate range of viscosity, molten glass can be subjected to many
different processes to make products ranging from flat sheets several square meters in area to
filament with diameter les than that of a hair.

· Annealing:

Although glass contracts on cooling like other materials but due to its low thermal
conductivity, it does not cool uniformly which can produce uncontrolled stress in the glass
and can break the glass. This undesirable stress can be avoided by slow and controlled
cooling which is the annealing process. Annealing is carried out in a part called lehr, through
which the glass passes on a slow moving conveyor.

When glass products have been formed, annealed and cooled to an appropriate temperature, they
are subjected to a range of finishing products.

· Toughening or tempering

In order to avoid breaking, glass is thermally strengthened by inducing compressing stresses

in the outer surfaces. Toughening is carried out by reheating the glass uniformly to a
temperature just above which deformation can take place and then rapidly cooling the
surfaces. Although cooling chills the outer layers while the center of the glass is still hot. As
the center of the glass cools, it contracts pulling the rigid surface layers into compression
which is further balanced by the tension in the inner layer. This method of strengthening can
be applied to flat glass or simple shapes such as windscreen.
It is possible to toughen certain articles chemically by ion exchange.

· Coating:

Coating process have been developed for decoration, protection and strengthening and for
technical reasons. Coatings are applied at two stages:
Hot end coatings are applied immediately when the containers have left the forming machine
and before they enter the annealing lehr
Cold end coatings are applied just before the annealed containers leave the lehr.
The coatings are applied via chemical vapour or a spray. The coating can change the
absorption and the optical properties of the glass.

Forensic Science PAPER: CRIMINALISTICS AND FORENSIC PHYSICS

TOPIC: MANUFACTURE OF GLASS PART 1
____________________________________________________________________________________________________

· Coloring and decolorizing:

Unless the raw materials are pure, glass made from silica and other raw materials will appear
green, the coloration depending mainly on the amount of iron oxide and other impurities. But
for some products the manufacturers decolorize the glass by adding small amounts of
colorants which are complementary to green color so that the finished articles appear to be
colorless.

· Cutting:

The final stage of glass making is cutting in which diamond wheel cutters are used to cut the
glass made to the required size. Customer requirements are fed into the computer to find out
the best way to cut the glass to avoid waste.

5.Summary
To summarize, we have studied one of the oldest methods that is the Float Glass method for the
manufacture of glass introduced by Sir Alastair Pilkington. This is used to make flat glass,
window glass etc.

Forensic Science PAPER: CRIMINALISTICS AND FORENSIC PHYSICS

TOPIC: MANUFACTURE OF GLASS PART 1
 SUBJECT FORENSIC SCIENCE

Paper No. and Title Paper No. 7: Criminalistics and Forensic Physics

Module No. and Title Module No. 15: Manufacture of glass Part 2 -
Glass Blowing Technique
Module Tag FSC_P7_M15

FORENSIC SCIENCE PAPER No. 7: Criminalistics and Forensic Physics

Module N0. 15: Manufacture of Glass Part-2: Glass
Blowing Technique
 TABLE OF CONTENTS

1. Learning Outcomes

2. Introduction to glass blowing technique

3. Glass Blowing technique

4. Modern Glass Blowing Technique

5. Summary

FORENSIC SCIENCE PAPER No. 7: Criminalistics and Forensic Physics

Module N0. 15: Manufacture of Glass Part-2: Glass
Blowing Technique
 Rid

1. Learning Outcomes
In this module, you shall be able to learn about the second method of manufacture of
glass namely

 Glassblowing Technique

2. Introduction to glassblowing technique

Glassblowing technique is another technique apart from float glass process, for the
manufacture of glass. This technique is used for the production of glass bottles and
containers. In this process, the molten glass is inflated into a bubble with the help of a
blow pipe. Then the glass is manipulated with the use of a torch on a smaller scale for
producing precision glassware. A glassblower, glassmith, or gaffer is an individual who
blows glass whereas the one who manipulates glass with the help of torch is known as
lamp worker. This is generally done on smaller scale.

3. Glass blowing process

Principle:

 The glassblowing technique exploits one of the working properties of glass which
was previously unknown to the glassworkers that is inflation. When a small
amount of air is introduced in glass, it results in the expansion of the molten part
of glass. This process is known as inflation. The property of inflation is centered
on that the atoms in the liquid state of glass are bonded together by strong
chemical bonds in a random and disordered fashion. Thus, the molten glass is
viscid sufficiently to be blown and progressively hardens due to loss of heat.

 In order to upsurge the rigidity of the molten glass and to expedite the manner of
blowing, a refined change in the composition of glass was done. Fischer and
McCray postulated that the lower concentration of natron, which acts as a flux in
the manufacture of glass, makes the glass stiffer for blowing.

FORENSIC SCIENCE PAPER No. 7: Criminalistics and Forensic Physics

Module N0. 15: Manufacture of Glass Part-2: Glass
Blowing Technique
  When the glass is blown the thin layers are more viscous than the thick layers
because the former layers cool faster than the thick ones.

Glass Blowing Techniques:

There are two major methods.

 Free-blowing glass blowing and

 Mold-blowing

 Free-blowing glass blowing

Although introduced in the 19th century, this technique is still widely used nowadays for
creative purposes. The process of free-blowing involves the blowing of short puffs of air
into a molten portion of glass called “gather". This is coiled at one end of the blowpipe
with the consequence of making an elastic skin on the inside of the glass blob that
matches the external skin produced by the exclusion of heat from the furnace. The
glassworker then inflates the molten glass to a coherent blob and works it into a desired
shape.

 Example:

One of the examples of this technique is Portland Vase, which is a cameo manufactured
during the Roman period. Experimentation was carried out by Gudenrath and Whitehouse
with the purpose of reinventing the Portland Vase. Mainly, the blue glass needed for the
body of the vase was collected on the end of the blowpipe that was consequently
immersed in a container having hot white glass. Inflation took place when the
glassworker blew the melted glass in to the sphere. The sphere was then stretched or
elongated into a vase with a layer of white glass overlying the blue body.

FORENSIC SCIENCE PAPER No. 7: Criminalistics and Forensic Physics

Module N0. 15: Manufacture of Glass Part-2: Glass
Blowing Technique
  Bold blowing

Mold-blowing was another glassblowing method which came after the invention of free-
blowing. A globule of melted glass is put on one end of the blowpipe and inflated into a
mold made up of carved metal or wood. Hence, texture and shape of the glass is
determined by the formation on the inside of the mold and not on the skill of the worker.

Usually, just two types of molds, namely single-piece mold and multi-piece mold, are
used to produce mold-blown vessels. The single-piece mold permits the finished glass
object to be detached in one movement by pulling it up from this mold. It is largely
employed to create glassware and effective vessels for storage and transportation. While
the multi-piece mold is made in multi-paneled mold segments that join together to
develop a more sophisticated surface modeling, texture and design.

4. Modern Glass Blowing Technique

The Modern Glassblowing involves three furnaces:

 The Furnace: It contains a crucible of molten glass

 The glory hole: It is used to reheat a piece in between steps of working with it.

 The lehr or annealer: It is used to gently cool the glass ranging from few hours to
days, dependent on the size of the pieces because it protects the glass from
stresses caused by temperature thereby keeping it safe from cracking or
shattering.

Many glassblowing studios in Mexico and South America still employ this method.

The major tools used by a glassblower and the process are as follows:

The blowpipe (or blow tube), punty, bench, marver, blocks, jacks, paddles, tweezers,
paper, and a variety of shears.

FORENSIC SCIENCE PAPER No. 7: Criminalistics and Forensic Physics

Module N0. 15: Manufacture of Glass Part-2: Glass
Blowing Technique
 Process:

 To start with, the blowpipe is preheated and dipped in molten glass

 The molten glass is gathered at the end of the blow pipe and rolled on a marver,
which is a flat sheet of steel. (Marvering)

 Marvering forms a cool skin on the exterior of glass blob, thus shaping it

 The air is then blown creating a bubble. To make a larger piece, the glass worker
gathers more glass over that bubble.

 After giving the piece its final size, the bottom is finalized

 The molten glass is then attached to an iron or a stainless steel rod called punty
for shaping and transferring the piece from blowpipe to shape the top

Apart from the blow pipe, punty and marver, the use of other major tools is as follows:

 The bench is the workstation with a place for the glass blower to sit, a place for
hand held tools and two rails on which the punty rides while the glass blower is
working on the piece to be prepared.

 Blocks are ladle-like tools made from water-soaked fruitwood and are used with
marver to shape and cool a piece in the early steps of creation.

 Jacks are tools shaped like large tweezers with two blades and are used for
forming shape later in the creation of a piece.

 Paddles are flat pieces of wood or graphite which are used for creating flat spots
such as a bottom.

 Tweezers are used to pick out details or to pull on the glass.

 Shear: two important types; straight and diamond. Straight shears are large bulky
scissors for making linear cuts while diamond shears have diamond shaped
blades(when partially open), used for cutting masses of glasses.

FORENSIC SCIENCE PAPER No. 7: Criminalistics and Forensic Physics

Module N0. 15: Manufacture of Glass Part-2: Glass
Blowing Technique
 Applying patterns and color to the blown glass:

 Frit can be defined as the large pieces or powdered color that is rolled over the
molten glass.

 Complex and detailed patterns can be created through the use of canes which are
rods of colored glass and murrine which are the rods cut in cross-sections to
reveal patterns. The colored pieces can be arranged on a flat surface in a
characteristic form and picked by rolling out a dollop of hot glass.

 Example: Reticello technique: It involves creating two bubbles from cane, each
one of them twisted in a different direction and then combing them while blowing
out the final form.

5. Summary

 In this module, we have studied another technique for glass making which is the
glass blowing technique.
 This technique is majorly used to produce glass bottles, glass containers, creative
glass vase, glass with complex patterns etc. there are two major techniques
involved: free blowing and mold blowing.
 This has extended to the modern glass blowing techniques.

FORENSIC SCIENCE PAPER No. 7: Criminalistics and Forensic Physics

Module N0. 15: Manufacture of Glass Part-2: Glass
Blowing Technique
 SUBJECT FORENSIC SCIENCE

Paper No. and Title Paper No. 7: Criminalistics and Forensic Physics

Module No. and Title Module No. 16: Physical Properties of glass and glass
fractures
Module Tag FSC_P7_M16

FORENSIC SCIENCE Paper No. 7: Criminalistics and Forensic Physics

Module No. 16: Physical properties of glass and glass
fractures
 TABLE OF CONTENTS

1. Learning Outcomes

2. Introduction

3. Brief review of physical properties of glass

4. Types of glass fractures

5. Summary

FORENSIC SCIENCE Paper No. 7: Criminalistics and Forensic Physics

Module No. 16: Physical properties of glass and glass
fractures
 Ridge

Characteristic

1. Learning Outcomes
In this module, you will be able to know about

 The physical properties of glass that makes the examination of glass easy for
forensic investigators.
 The types of glass fractures.

2. Introduction
The knowledge about the physical properties of the glass makes the examination of the
glass easier for the investigating team as glass is frequently encountered in various crimes
such as burglary, road accidents, murders, sexual assaults, shooting incidents etc. For
example, the pieces of broken glass from a glass window or a glass door may get stuck in
the suspect’s shoes or garments while committing the crime or pieces of headlight glass
of suspected vehicle may be found at the scene of hit and run accident can act as strong
clues to confirm the crime. Thus, we can say that the glass forms one of the most
common evidentiary materials in many criminal investigations.

3. Physical properties of glass - a brief review

The study of the physical properties of the glass offers a direct means of recognition of
the glass fragments found at the crime scene. If the fragments are very small, it forms the
basis of identification. These properties are constant for a glass of definite and consistent
composition and are useful for investigation. The variations in the composition of glass
cause variations in the physical properties from one glass object to another.

Some of the physical properties of the glass are as follows:

Density:

The density of each substance is the mass per unit volume of the substance at a specified
temperature. Its units are grams/milliliter or Kg/liter, where mass refers to the amount of
matter in an object independent of gravity.

FORENSIC SCIENCE Paper No. 7: Criminalistics and Forensic Physics

Module No. 16: Physical properties of glass and glass
fractures
 It is an intensive property of matter that remains constant irrespective of the size of the
sample. It is considered as a characteristic property of glass and is thus used as an aid in
identification of the sample of the glass involved in the crime as different types of glasses
like window glass or headlight glass have got different densities.

The density of the glass pieces can be determined either by floatation or density gradient
method.

Refractive index:

Light waves travel with a constant velocity until they pass through another medium apart
from vacuum such as glass, where at the point of contact the light bends and suddenly
slows down. This bending of waves because of the change in the velocity of light is
called refraction, while the ratio of speed of light in vacuum to the speed of light in the
medium or substance like glass is called the refractive index of the substance.

That is, n=c/v, where n is represented as the refractive index, c is the velocity of light in
vacuum while v is the velocity of light in the substance.

It is also referred to as ratio of sine of angle of incidence to the sine of angle of refraction.

This property also characterizes a substance and is thus useful in its identification.
Different types of glasses like television glass (1.49), window glass (1.51) etc. have got
different refractive index which makes possible their identification.

The refractive index varies with the wavelength of light and also with temperature which
makes possible its measurement by the immersion method.

Dispersion:

All transparent objects like glass slows down the shorter wavelengths of light more than
the longer wavelengths and thus the refractive index is higher for shorter wavelengths
than for longer wavelengths. This process is called dispersion. In other words, the
splitting of white light into its constituent colors when it passes through a transparent
object like a glass prism is called as dispersion. The coefficient of dispersion is expressed
as a change in the refractive index between two specified wavelengths.

FORENSIC SCIENCE Paper No. 7: Criminalistics and Forensic Physics

Module No. 16: Physical properties of glass and glass
fractures
 Colour:

The colour is used for identification on the occasion when the glass fragments involved in
a crime are coloured for example decorative glasses, or bottles. Even the glasses that
seem to be colorless have been found to have some tint, hence when the fragments of
glass available are large, their colours should be compared.

Ultra violet fluorescence:

Although most of the glass samples don’t show the property of fluorescence or show little
fluorescence, some types of glass fluoresce with colours which may be blue, violet,
brown, purple or green when examined in Ultra violet light. Thus, in some cases it
becomes useful in distinguishing between different glasses.

Hardness:

Since glasses vary appreciably in hardness, this property becomes actually useful for
differentiation between different glasses.

3. Types of glass fractures or fragments

Most of the strength of the glass is in its surface. Glass has less tensile strength than
compressive strength. So, the glass bends to any force which is exerted on any one of its
surface. But the glass breaks due to tensile stresses that pulls the surface of the glass apart
and hence exceeds the elastic limit. Imperfections, flaws or minor damage in the surface
of the glass such as scratches, bruises or etching which we call as glass fractures, reduce
the tensile strength at those points in the surface and hence reduce its tensile strength.

The study of the glass fractures gives a lot of information about the crime. For example, a
fractured window glass will reveal information that can be related to the force and the
direction of an impact which is useful in reconstructing the crime.

When there are a lot of pieces of glass in a sample, it is advised to assemble them to
know whether the glass fragments come from one or more than one object which can
reveal the brand or the pattern of the original object.

FORENSIC SCIENCE Paper No. 7: Criminalistics and Forensic Physics

Module No. 16: Physical properties of glass and glass
fractures
 A glass that has broken while committing a crime shows primarily two kinds of fractures
that is primary or first made fractures and secondary or subsequent fractures. Primary
fractures are called radial fractures while the secondary fractures are called concentric
fractures.

They look like the spokes of a wheel as they radiate outwards from the point of contact.
Concentric fractures form a series of broken circles or arcs around the point of contact.

They are as follows:

Radial fractures:

Radial fractures are produced on the surface opposite to the one where the force had been
applied. When an external force is applied on one side of a glass, then the glass sheet
bends away from the force so that the tensile stresses are set up in the opposite surface of
the sheet while the compressive stresses are developed on the surface to which the force
has been applied. If the applied force is so strong to have exceeded the elastic limit, the
glass breaks, invariably from a point where a tensile stress of sufficient magnitude has
developed. In a glass sheet, the primary or the initial rupture which we call as radial
fracture tends to be star shaped or appears like spokes of a wheel. In other words, it
spreads from this point of contact as a series of cracks in a number of random directions
as shown in the figure.

For example, penetration caused in the window by a projectile or a bullet produces a

pattern in which crack radiates outwards and encircle the hole.

Concentric fractures:

But, if the force continues even after radial fracture, especially when the instrument is
either blunt or tapers abruptly, there is bending movement that causes tensile stresses to
develop on the side of the glass to which the force was applied. This leads to a series of
cracks known as concentric fractures which connect with the adjacent radial fractures.

Concentric Fractures

The concentric fractures form a series of broken circles or arcs, around the point of
contact.

FORENSIC SCIENCE Paper No. 7: Criminalistics and Forensic Physics

Module No. 16: Physical properties of glass and glass
fractures
 5. Summary

 Glass is one of the major sources of evidence on the crime scene.

 The knowledge of the physical properties of the glass act as a valuable source of
information for the forensic people.
 The examination of the broken glass can help to reconstruct the crime by knowing
the source of the force that has been responsible for breaking the glass under
consideration.

FORENSIC SCIENCE Paper No. 7: Criminalistics and Forensic Physics

Module No. 16: Physical properties of glass and glass
fractures
 SUBJECT FORENSIC SCIENCE

Paper No. and Title Paper No. 7: Criminalistics and Forensic Physics

Module No. and Title Module No. 17: Direction of impact and glass fractures
in detail
Module Tag FSC_P7_M17

FORENSIC SCIENCE Paper No.7: Criminalistics and Forensic Physics

Module No. 17: Direction of impact and glass fractures in
detail
 TABLE OF CONTENTS

1. Learning Outcomes

2. Introduction

3. Glass as a physical evidence

4. Direction of impact cone and glass fractures

5. Summary

FORENSIC SCIENCE Paper No.7: Criminalistics and Forensic Physics

Module No. 17: Direction of impact and glass fractures in
detail
 Ridge Characteristic

1. Learning Outcomes
In this module, you shall be able to learn about

 The points to be taken care of while considering glass as a physical evidence

 The direction of impact cone
 Types of fractures in detail which is based on the impact

2. Introduction
Glass is one of the commonest evidentiary materials in many investigations. The
information gathered from glass occurring as physical evidence depends on the samples
available, how the glass has been broken and the care with which the samples have been
gathered.

Most of the information depends on how the glass has been broken and fractures formed.

3. Glass as a physical evidence

Considering glass as a physical evidence and if suitable samples are available , then first
the glass pieces are assembled which can actually help the scientists to know whether the
fragments are from more than one glass which can further reveal the brand or pattern of
the original object.

After this, the scientists look for the following physical appearances on the glass:

 The type of force which caused the fracture,

 The origin of fracture,
 The direction of force causing the fracture,
 Order of occurrence of multiple fractures,
 Whether the particular fragment has come from a particular kind of broken glass
object, for example window, bottle, head light,
 Whether a fragment has come from a particular place or a particular object.

FORENSIC SCIENCE Paper No.7: Criminalistics and Forensic Physics

Module No. 17: Direction of impact and glass fractures in
detail
 4. Determination of direction of impact cone and glass fractures

 Direction of impact cone

The patterns on the glass fractures can actually reveal the direction of the projectile. The
pattern can actually reveal whether the object that caused the fracture was moving at a
low pace like a rock or a fast moving bullet, whether it is a thermal stress or impact. This
can really be critically important in reconstructing the crime scene.

For example, if a bullet strikes a window and penetrates it, while not completely
shattering it, it may leave a hole with surrounding fractures or may not. On the side of
impact the bullet will create a clean hole while on the opposite, a cone shaped corner of
glass is forced out. Thus, visual inspection can reveal the direction of impact.

 Glass fractures

Depending on whether the fracture is caused by a high velocity projectile or a low

velocity projectile, there are different kinds of fractures:

 Radial Fractures :

This we have already studied in the last module. To be precise, this may occur in
both the cases, that is low or high velocity projectile.

 Concentric Fractures:

These also we have studied in detail in the last module.

 Broken edges:

When there is a cut in the surface placed under tension, the glass may not break
squarely across. When a piece of glass is broken by bending from a larger piece,
the sharp edge remaining on the larger piece will probably be there on the side to
which the force was applied.

FORENSIC SCIENCE Paper No.7: Criminalistics and Forensic Physics

Module No. 17: Direction of impact and glass fractures in
detail
  Hertzian Fracture or cone:

Usually the glass breaks by tension and not by compression. For example, when
one pushes window glass, it begins to break from the back side and not from
where the force has been applied. It breaks under tension as tensile strength of
glass is always less than the compressive strength.

As far as failure of tension is concerned, it is not the only mode for breaking a
glass. If this would have been the case, the glass would then be impossible to
break as it would be unable to bend and create tensile stress. There is a second
mechanism by means of which the glass may be broken is by the formation of
Hertzian cone or fracture.

A hertzian cone is a cone of force that propagates through a brittle, amorphous or

crystalline solid from a point of contact, like a bullet through glass.

This occurs usually during very high energy impact. In such cases of high speed
and high energy impact, a compressive stress wave will pass through the glass
from the point of impact to the opposite side. Such situation is also referred to as
dynamic loading.

When a projectile strikes a glass pane, longitudinal compression waves are

generated, beginning at the point of impact and then moving outwards in a series
of spherical wave fronts which travel with the speed of sound in glass. The wave
travels almost 20 times the speed of the bullet fired.

When the stress wave arrives at the opposite side of glass, it is reflected and then
becomes a tension wave. Upon striking the impact side, it will be reflected again
as a compression wave and again launched towards the opposite side. This
interactive process results in the interference of tension waves if they are
coincidentally in phase. The amplitude of the waves will be additive and as a
result due to the accumulation of tensile strength results in the failure of glass.
Thus, a flake of glass is ejected from the opposite side. The largest flakes are at
the edge boundary while successive flakes that are close to the point of
application are smaller.

FORENSIC SCIENCE Paper No.7: Criminalistics and Forensic Physics

Module No. 17: Direction of impact and glass fractures in
detail
 Glass that has been broken in this fashion results in crater, opening away from the
direction of origin of space. The direction of crater depends on the speed of
propagation of projectile:

 In case of low velocity projectiles such as pebbles, a crater may be formed on the
opposite side of the glass but with no hole or a very small hole, even though the
projectile does not pass through the glass.
 If a projectile approaches in a perpendicular fashion, crater is symmetrical.
 In case of a high velocity projectile, such as a rifle bullet, will yield a small hole
with minimum flaking around circumference. A slow moving bullet however,
delivers more irregular hole with substantially more flaking.
 If an intermediate target has reduced the velocity of the projectile to even below
200fps, the glass may show evidence of tension propagated fracture with no crater
formation.

 Fractures in container glasses

There is a single location at which the fracture begins which we call as fracture
origin. Very rarely the fracture will traverse the thickness of the glass wall to the
opposite surface as well as being propagated away from fracture origin. The
fracture in the containers arises due to the following stress conditions:

 Internal pressure: If a glass container fails due to excessive internal pressure the
typical fracture appearance is a straight, vertical split in the sidewall of the
container which results may be due to the excessive carbon dioxide in beverages,
from thermal expansion of liquids due to heat or generation of gas due to
decomposition of contents. It usually originates at the heel or bottom where
stresses are greater. These rarely originate in the neck of the bottle as the neck is
stronger than the sidewall option.

After the initial fracture, it often forks at both ends, producing a series of fractures
that are symmetrical about the initial longitudinal fracture that is it is like a fan
shaped pattern. As the fan shaped pattern diverges, it travels through the
circumference and separates the neck and base from the rest of the portion.

FORENSIC SCIENCE Paper No.7: Criminalistics and Forensic Physics

Module No. 17: Direction of impact and glass fractures in
detail
  Thermal fracture: if very hot liquids are poured in cold glass or very cold liquid
is poured in hot glass, a thermal shock is produced leading to fractures. These
occur in the bottom of the container around circumference with no or very rare
surface markings resulting in fracture along the long axis of the container.

 Impact fractures: these generate the most complex stresses of any type of
fracture. There are three distinct phases of impact fracture: contact stress, flexure
stress and hinge stress, although the actual physical appearance of the fracture
will be determined by the one which is dominant.

Contact stresses: They are generated at or very close to the point of application of
the impact force resulting in Hertzian Fracture or results in chips along the mouth
of the container.

Flexure and hinge stresses: They arise from localized defect on the inside of the
glass. A very slight impact would be enough to cause the container to fail. This
will result in a star like appearance on the inside of the container while at the
same time causing the bending of glass wave to the outside. The stress created by
this outward bending is the hinge stress. Hinge stress fractures generally occur at
the same height as the initial flexure fracture at about 45 degrees.


5. Summary

 The physical appearance of the broken glass can actually tell the direction from
where the gun shot is coming, at what speed, with what force, how it leads to
fractures and under what circumstances different types of fractures have formed
both in flat glass and the glass containers.

FORENSIC SCIENCE Paper No.7: Criminalistics and Forensic Physics

Module No. 17: Direction of impact and glass fractures in
detail
 SUBJECT FORENSIC SCIENCE

Paper No. and Title Paper No. 7: Criminalistics and Forensic Physics

Module No. and Title Module No. 18: Markings on the Glass

Module Tag FSC_P7_M18

FORENSIC SCIENCE Paper No. 7: Criminalistics and Forensic Physics

Module No. 18: Markings on the Glass
 TABLE OF CONTENTS

1. Learning Outcomes

2. Introduction

3. Rib marks

4. Hackle marks

5. Backward fragmentation

6. Summary

FORENSIC SCIENCE Paper No. 7: Criminalistics and Forensic Physics

Module No. 18: Markings on the Glass
 Ridge Characteristic

1. Learning Outcomes

In this module, you shall be able to learn about

 Rib marks
 Hackle marks
 Backward Fragmentation

2. Introduction
On the examination of fractured glass different types of markings can be observed which
tells about the direction of the force and the stress on the glass. Depending upon whether
the hit is a direct hit or in other words whether the force applied is perpendicular to the
glass or side ways that is right to left or left to right. Different markings characteristic of a
fracture, are observed on the glass. This makes the first step in the examination of glass a
bit simpler.

3. Rib marks
When on examination of the fractured edges, if curved markings like waves are observed,
then these markings are called Rib Markings. The convexity of these marks actually
indicates the direction of travel of the bullet. They appear perpendicular to the surface at
which the crack is originated and then curve asymptotically (that is meeting at infinity)
with the opposite surface.

The direction of travel of the crack, along the glass, is from the concave side of the rib
marks to the convex.

The rib marks being almost at right angles to the face of the glass on which the crack has
opened, it has been observed that on radial fractures the rib marks are perpendicular to
the face opposite to which the force has been applied while on the concentric fractures,
the rib marks are perpendicular to the face on which the force has been applied (the crack
opens on the opposite face to the point of contact). The examination and thus the
interpretation of these fractures are used to determine whether a window has been broken
from inside or outside. Thus, it is necessary to determine as to which surface of the
broken pieces of glass under consideration, were originally interior or exterior.

FORENSIC SCIENCE Paper No. 7: Criminalistics and Forensic Physics

Module No. 18: Markings on the Glass
 Rib marks are the most conspicuous of all the glass edge markings, curved shell like
marks. These are also called conchoidal marks or Wallner lines. We know that a fracture
propagates perpendicular to the principal tensile strength, due to which the fractures tend
to orient themselves in such a way that they continuously remain perpendicular to the
principal tensile stress. So, when examining a radial fracture, the chonchoidal lines meet
the side opposite to the force at nearly right angles and then curve back asymptotically
towards the side from which the force was applied but in concentric fractures, the
tension is on the surface facing the force. So when the glass breaks due to tension failure,
the fracture is initiated on the side facing the force, the curved Rib marks or chonchoidal
marks will now meet the side which is the side facing the force at almost right angles.

4. Hackle Markings
Hackle markings are found in that area on the fractured surface where there has been a
relatively high stress. These markings actually consist of ridges running in the direction
of fracture propagation and are at right angles to any rib markings which may be internal.
They are most prevalent when the fractured surface runs at an angle of 45 degrees to a
pre-existing free surface.

Thus, hackle markings are a definitive indication of the direction of propagation. There
are two types of hackle marks:

Twist hackle: They appear at the region where the tensile stress twisted from crack
surface. Twist hackle can be generated by the primary crack as it travels through the
body, especially as it goes around the corners or geometric irregularities or if the stress
conditions change.

Mist hackle: They appear around the origin. They are also called velocity hackles.

5. Backward Fragmentation
If a glass breaks as a result of mechanical impact then a large number of small glass
particles will be generated and is projected for a considerable distance from breaking
object. The projection of glass particles back towards the person or object breaking a
window is known as backward fragmentation. This is the actual means by which
someone who is breaking a window acquires glass particles on his or her clothing. (If a
glass breaks under thermal shock then it has an irregular pattern and produces far fewer
small particles than an impact break.)

FORENSIC SCIENCE Paper No. 7: Criminalistics and Forensic Physics

Module No. 18: Markings on the Glass
 In detail, whenever a sheet of glass is bent so that there is a tensile strain on one surface,
there is actually a compressive strain on the other surface. When the glass breaks at the
surface under tension, the crack travels to the surface under compression so that the
whole compressive force is exerted along the broken edges in contact. This causes flakes
to be split off the broken edges of the glass sheet at the compressed surface and these
chips frequently fly off with considerable velocity. Chips from radial fractures come from
the side of the glass to which the force was applied and travel in the direction opposite to
the force.

6. Summary

 In this module we have learnt the three different kinds of markings rib marks,
hackle marks and backward fragmentation which are helpful to interpret the
direction of impact and the strength of the force.
 In determining the direction of force, only those pieces that are close to the point
of origin are suitable for interpretation.
 It is advisable not to select for examination a piece that is very close to a frame, as
the rigidity with which such a piece was held may influence the nature of the
fracture feature.

FORENSIC SCIENCE Paper No. 7: Criminalistics and Forensic Physics

Module No. 18: Markings on the Glass
 SUBJECT FORENSIC SCIENCE

Paper No. and Title Paper No.7: Criminalistics and Forensic Physics

Module No. and Title Module No. 19: Identification by shape, size and fit

Module Tag FSC_P7_M19

FORENSIC SCIENCE Paper No.7: Criminalistics and Forensic Physics

Module No. 19: Identification by shape, size and fit
 TABLE OF CONTENTS

1. Learning Outcomes

2. Introduction

3. Thickness

4. Curvature

5. Physical matching

6. Color

7. Fluorescence

8. Hardness

9. Surface features

10. Summary

FORENSIC SCIENCE Paper No.7: Criminalistics and Forensic Physics

Module No. 19: Identification by shape, size and fit
 Ridge Characteristic

1. Learning Outcomes
In this module, you shall be able to learn about how the glass fragments are identified
according to
 Thickness,
 Curvature,
 Actual physical fit,
 Color,
 Fluorescence,
 Hardness,
 Surface features.

2. Introduction
A preliminary examination of the surface of the glass will indicate the source that is a flat
surface may be from a window glass or plate glass, a cylindrical surface from a bottle, a
spherical surface from a spectacle glass or head lamp glass. This examination is done
considering that the two glasses do not have a common origin. This examination is
achieved by considering surface texture, pattern, colour etc.

The general condition of the glass should be inspected minutely using a stereo
microscope even before cleaning. Moreover, it is desirable to select glass fragments with
edges that appear freshly broken.

3. Thickness
For a sheet of glass and if the pieces of smaller sample have portions of both the surfaces
present, then it becomes more useful to measure the thickness using a micrometer screw
gauge. The thickness of the glass sheet may vary from one place to the other and may not
have uniform thickness throughout. Thus, it becomes beneficial to study the variations in
their thickness before comparing the thickness of the controlled sample and that of the
crime exhibit.

A micrometer screw gauge incorporates a calibrated screw mostly used for precise
measurements of components.

FORENSIC SCIENCE Paper No.7: Criminalistics and Forensic Physics

Module No. 19: Identification by shape, size and fit
 4. Curvature
Determination of curved surface can help distinguish that glass from other types of glass
like containers or decorative glasses. A spherometer is used to measure the radius of
curvature of the glass fragments having curved surface.

The radius of curvature is found using the following formula:

R= (l2/6h) + h/2
Where l = mean distance between the legs of the spherometer
And
h = height of the curved surface.

If the glass fragments are large then stereomicroscope is used.

5. Physical Matching or fit

Physical fit between two glass fragments actually is the best method but due to different
types of fractures generated in glass, physical fit is rare. It requires the edges of one
fragment to perfectly fit into an edge of another.

A complementary lateral fit along the broken edges over a length of 1/4th an inch or more
establishes that the two glass fragments were continuous before breakage. The match is
3D, so under stereomicroscope the edges of the samples are carefully observed which
will exactly fit into each other.

Lateral pressure has to be applied, in order to see that the small irregularities intermesh
and hold the pieces together, so that one can feel the sense of exact fit along the broken
edges.

6. Color
On some very rare occasions when glass fragments associated with a crime are colored,
for example, decorative glasses or bottles, then the color would be used for exclusion or
identification. Even colorless glasses are usually found to have some perceptible tint, thus
when the large fragments of glass are available, their color should be compared.

FORENSIC SCIENCE Paper No.7: Criminalistics and Forensic Physics

Module No. 19: Identification by shape, size and fit
 Comparing color can distinguish between two or more sources of glass. Sample size may
affect apparent color; therefore, side by side comparisons should be made of approximate
equal and sufficient size. Pieces of at least 5mm are desirable. The fragments are placed
on white background, for example, fine filter paper, and the comparison is made in bright
diffused daylight. The examination will be able to distinguish between the true color of
the glass and the color of any coatings that may be on the surface of the glass.

Observing the glass, using both fluorescent and incandescent light is useful in
distinguishing different colors or tints using a spectrophotometer.

But most of the time, it is not possible to compare the color of microscopic glass
fragments due to insufficient color density.

7. Fluorescence
Although most of the glass samples exhibit little or no fluorescence, some types of glass
fluoresce with colors which may be blue, violet, brown, purple or green when examined
in ultraviolet light. Hence, in most of the cases it is very useful in distinguishing between
different glasses.

This examination is done by observing glass fragments over a non-fluorescent

background by illuminating it consecutively by short wave (254nm) and long wavelength
(350 nm)UV light.

While comparing fluorescence, fragments of similar thickness should be used. But,

before comparison, a thorough washing to remove oil, grease or other possible
fluorescent foreign debris on the glass surfaces is absolutely necessary.

8. Hardness
Since glasses vary appreciably in hardness, this property may also be used for
differentiation.

The hardness determination is possible on an arbitrary scale and requires internal

standards. Thus, two fragments can be compared for hardness by determining their
mutual scratching powers. If the hardness difference is small, then it becomes helpful to
study the scratches or attempted scratches under a low power binocular microscope.

FORENSIC SCIENCE Paper No.7: Criminalistics and Forensic Physics

Module No. 19: Identification by shape, size and fit
 9. Surface Features
Surface features can be formed either intentionally or accidentally during manufacturing
or fabricating processes. These form another basis of comparison to distinguish between
different sources of glass. They can serve as identifying features while examining the
glass fragments for fracture match if the feature is present on both the fragments. Surface
features include coatings, thin films and mirrored backings, etching, texturing etc.

Coatings or thin films:

Coatings or thin films are usually seen on architectural or automotive glass. These films
are actually done to increase the durability of glass and are composed of wide variety of
materials in single or multiple layers. They may be amorphous or polycrystalline.

The thickness of coating can range from nm (thin films) to mm (mirrored). Coatings can
be applied to either one or more surfaces. Since it is not possible to distinguish coatings
so instrumental methods of analysis like X-ray Diffraction etc.

Manufacturing features:

Intentional surface features include etching, texturing, frosting etc. while accidental
surface features are as a result of manufacturing that include rouge pits, polishes etc.
They can be compared visually very easily.

Additional surface features:

This is nothing but distinguishing between glass fragments in terms of scratches,

abrasions etc. on them. These should be examined and characterized carefully using
stereomicroscope before cleaning.

10. Summary

 In this module, we have studied the importance of interpreting, analyzing and thus
comparing two glass fragments on the basis of major physical features of glass.
 These physical features include the thickness, hardness, physical matching, color,
fluorescence, curvature, some surface features like coatings, thin films, etching,
texturing etc.

FORENSIC SCIENCE Paper No.7: Criminalistics and Forensic Physics

Module No. 19: Identification by shape, size and fit
 SUBJECT FORENSIC SCIENCE

Paper No. and Title PAPER No. 7: Criminalistics and Forensic Physics

Module No. and Title MODULE No.20: Density measurements of Glass

Samples
Module Tag FSC_P7_M20

FORENSIC SCIENCE PAPER No.7: Criminalistics And Forensic Physics

Module No.20: Density Measurements of Glass Samples
 TABLE OF CONTENTS

1. Learning Outcomes

2. Introduction

3. Importance and use of density measurements

4. Pre-requisite for density measurement

5. Different methods for density measurements

6. Summary

FORENSIC SCIENCE PAPER No.7: Criminalistics And Forensic Physics

Module No.20: Density Measurements of Glass Samples
 Ridge Characteristic

1. Learning Outcomes
In this module, you shall be able to learn about

 The importance of density measurements

 Pre-requisites for density measurements
 How the density of glass samples are measured using the direct method or by
comparison

2. Introduction

Density measurement is one of the most important analyses for comparing the glass
samples under investigation. The comparison of densities can give a proof of a
connection, if at all, between a suspect and crime scene. If the density of a sample glass
specimen and the one under consideration do not matches then it can be proved that they
do not share a common source or origin. But, if the densities match and prove the origin
to be common, then it becomes very easy to trace the type of glass used by the criminal to
conduct the crime and can be helpful in leading the forensic expert to the suspect.

3. Importance and use of density measurements

Density can be actually useful to help knowing the composition of the glass sample. It is
defined as mass/unit volume of the sample.

Density being an intensive property does not depend upon the size of the sample. In other
words, it remains the same, regardless of the fact whether the sample is big or small. But,
it depends on the changes in the composition and is measured directly or by comparison.

This measurement is used only if elemental analysis is not available. Density

measurements should be done for samples more than 2 to 3 mm in size. These
measurements are useful in identifying multiple sources present in the sample.

FORENSIC SCIENCE PAPER No.7: Criminalistics And Forensic Physics

Module No.20: Density Measurements of Glass Samples
 4. Pre-requisite for density measurements

 Proper sample preparation that is the density measurement will not be appropriate
for cracked glass fragments or comparing bulk fragments. The cracks in the glass
sample can make the glass appear less dense than it really is.
 Density measurement and comparison between known samples and the suspected
samples should be done using fragments of equal size.
 Sample should be clean and dry.
 Since window glass does not have a uniform density, so care must be taken to
determine the variation in density of the known sample from different locations.
 Also the surface of the tempered glass is less dense than its interior, so one has to
be careful in taking measurements of several known samples.

5. Different methods for density measurements

These glass fragments under criminal investigations are very small and so the density of
such fragments can be determined either by Floatation Method or Density Gradient
Method.

Both the methods are based on the fact that the glass fragments will float in a liquid
medium having density greater than that of the fragments, while they will sink in a liquid
medium having density less than the fragments. But, they remain suspended in a liquid
whose density is same as that of the fragments. These methods are so accurate that they
can distinguish glass particles that differ in density by 0.001gm/cc.

For the heavier liquid, Bromoform or Methylene Iodide is used. For lighter liquid,
Xylene, Bromobenzene, Benzene, Nitrobenzene is used.

FORENSIC SCIENCE PAPER No.7: Criminalistics And Forensic Physics

Module No.20: Density Measurements of Glass Samples
 Heavier liquids

Bromoform (chemical symbol – CHBr3):

It is brominated organic solvent and pale yellow liquid at room temperature. It has high
refractive index, very high density (2.89 g/cc) and a sweet odor like chloroform.

Bromoform

Methylene iodide:
Also called Iodomethane, this is a chemical compound with symbol, CH3I. It has high
density (2.28 g/cc), is colorless and volatile liquid.

Methylene iodide

FORENSIC SCIENCE PAPER No.7: Criminalistics And Forensic Physics

Module No.20: Density Measurements of Glass Samples
 Lighter Liquids

Xylene (chemical symbol – C8H10):

Xylene or dimethyl benzene is an aromatic hydrocarbon mixture containing a benzene
ring with two methyl groups at various substituted positions. It has a low density of
0.864g/ml.

Xylene

Benzene (chemical symbol – C6H6):

It is an important organic compound. Each molecule is composed of six carbon atoms

joined in a ring with one Hydrogen atom attached to each Carbon atom. Its density is low
– 0.876 g/cc.

Benzene

FORENSIC SCIENCE PAPER No.7: Criminalistics And Forensic Physics

Module No.20: Density Measurements of Glass Samples
 Nitrobenzene (chemical symbol – C6H5NO2):

It is water insoluble pale yellow oil with almond like odor with density 1.20 g/cc. It freezes to
give greenish yellow crystals.

Nitrobenzene

Bromobenzene (chemical symbol – C6H5Br):

It is an aryl halide formed by electrophilic aromatic substitution of benzene using

bromine. It is a clear, colorless or pale yellow liquid with density 1.5 g/cc.

Bromobenzene

FORENSIC SCIENCE PAPER No.7: Criminalistics And Forensic Physics

Module No.20: Density Measurements of Glass Samples
 FLOATATION METHOD
 The crime and control glass piece (the one with known density) samples are
crushed to comparable size with similar shape which is one of the most important
steps. Each piece of glass is briefly sketched and marked for reference.
 A clean and dry sample of crime glass particle (which is again an important
precaution) is placed in a small beaker containing Bromoform. The glass will
float on the liquid surface indicating that the density of the liquid is greater than
that of the glass.
 The less dense liquid, Xylene is then added slowly, drop wise with stirring until
the particle is exactly suspended. One should be careful while adding the mixture
that it should be stirred with each addition so that air bubbles, if any are removed.
 Added similar size, clean and dry sample of control glass. If both the crime and
the control glass particles remain suspended in the liquid, then their densities are
equal to each other and to that of the liquid mixture. Particles with different
densities will either sink or float depending upon whether they are denser or less
dense than the liquid medium.
 The densities of the particles of the glass can be determined by calculating the
density of the floatation mixture using density meter.
 A portion of the floatation mixture is transferred directly to the density meter and
the density is thus recorded.

DENSITY GRADIENT METHOD

Density gradient method is a good method for examining the glass fragments, when there
are a number of glass fragments that is several unknown samples or several possible
sources.

 In this method, a vertical glass tube about 5mm in internal diameter and 10 to 18
inches long is sealed at one end and filled with successive layers of liquid in
decreasing density.
 In other words, the gradient is such that the density at any level is less than that of
any level lower in the tube and greater than that of any level higher in the tube.
 The standard gradient tube is made up of layers of two liquids mixed in varying
proportions, so that each layer has a different density.

FORENSIC SCIENCE PAPER No.7: Criminalistics And Forensic Physics

Module No.20: Density Measurements of Glass Samples
  When completed, a density gradient tube usually has 6 to 10 layers.
 In this experiment, one can not only compare glass particles but also calibrate the
density column.
 The first layer is the heavier of the two miscible liquids selected (for example:
bromoform is heavier while bromobenzene is the lighter one.
 The second layer is the mixture of three parts of heavy liquid and one part of the
light liquid.
 The third layer consists of equal proportion of both the liquids.
 The fourth layer consists of one part of the heavier liquid while three parts of the
lighter one.
 The fifth layer consists of light liquid only.
 The layers are added on each other carefully with the help of a pipette to avoid
mixture at the interface.
 The topmost layer and the last layer are taken in such a way that it is about one
fourth to the height of the column, while the second, third and fourth layers are
almost about half of the height of the first layer. The last or the top layer is of the
same height as the first layer.
 Care should be taken to keep the gradient tube overnight so that the liquids diffuse
into each other to form a gradient.
 The glass fragments should be carefully and gently placed in the tube and allowed
to settle down. These fragments will suspend in the portion having same density.
 Thus, the density of the liquid and hence of the fragments can be determined.

The densities of various glass and related materials are:

 Flat Window glass: 2.47 - 2.56
 Headlight glass : 2.47 – 2.63
 Mica : 2.6 – 3.2
 Quartz : 2.65
 Flint Glass : 2.9 – 5.9
 Diamond : 3.01 – 5.2

FORENSIC SCIENCE PAPER No.7: Criminalistics And Forensic Physics

Module No.20: Density Measurements of Glass Samples
 10. Summary
 Density measurements for very tiny glass fragments can help us gain knowledge
about the fragments under investigation.
 Density can be measured majorly by two methods, floatation and density gradient
method.
 These measurements can help in knowing the source of the glass used by the
criminal and can force the investigators to trace the criminal, if possible.

FORENSIC SCIENCE PAPER No.7: Criminalistics And Forensic Physics

Module No.20: Density Measurements of Glass Samples
 SUBJECT FORENSIC SCIENCE

Paper No. and Title PAPER No.7: Criminalistics and Forensic Physics

Module No. and Title MODULE No.21: Refractive Index Measurement for
Glass Samples - Part 1
Module Tag FSC_P7_M21

FORENSIC SCIENCE PAPER No.7: Criminalistics And Forensic Physics

MODULE No.21: Refractive Index Measurement for Glass
Samples - Part 1
 TABLE OF CONTENTS

1. Learning Outcomes

2. Introduction

3. Importance and use of refractive index measurement

4. Pre-requisite for refractive index measurement

5. Different instruments used for refractive index measurements

6. Different methods for calculating refractive index

7. Summary

FORENSIC SCIENCE PAPER No.7: Criminalistics And Forensic Physics

MODULE No.21: Refractive Index Measurement for Glass
Samples - Part 1
 Ridge Characteristic

1. Learning Outcomes
In this module, you shall be able to learn about

 The importance of refractive index measurements

 Pre-requisites for refractive index measurements
 Brief description of the methods for measuring refractive index followed by a
detailed description of some of the methods

2. Introduction
It is actually a forensic scientist’s duty to analyze glass fragments so as to clearly and
unambiguously determine the origin of a sample.

Every material has its own refractive index. The refractive index measurement can give
an indication of the composition and thermal history of glass. As a result, one can
actually know the make of the glass. As we know, that the light beam bends from its
original path on passing from one medium to another. This process of refraction is thus,
the basis of the different methods for determining the refractive index of the glass.
Refraction is much more evident in solids than in liquids or gases. Glass is indeed an
excellent medium for showing refraction. Refractive index measurement is affected by
types of glass according to its color, manufacturer and thickness. As it is difficult to
measure refractive index by direct method practically, so some indirect methods like
immersion methods, dispersion etc is used.

3. Definition and use of refractive index measurements

Refractive index is a dimensionless quantity which is characteristic of an optical medium
and is defined as the ratio of the velocity of light in vacuum to the velocity of light in the
medium.

That is,
n = c/v
Where, n is the refractive index of the medium, c is the velocity of light in vacuum and v
is the velocity of light in the medium.

FORENSIC SCIENCE PAPER No.7: Criminalistics And Forensic Physics

MODULE No.21: Refractive Index Measurement for Glass
Samples - Part 1
 It determines how much light is bent towards normal or away from normal (normal is the
line perpendicular to the interface of the two mediums) or in other words how much light
is refracted when the beam enters a material.

This is also described by Snell’s law given by

n1sin1 = n2sin

1 and 2 are respectively, the angle of incidence and the angle of refraction crossing the
interface between the two mediums with refractive indices n1 and n2.

Fig: refractive index

The velocity decreases when a beam of light is travelling from gas to solid. In other
words, the light bends downwards. This allows the determination of the refractive index
of glass that is how much light is refracted on entering the glass.

Since refraction is much more evident in solids than in gases or liquids, thus, glass is
indeed an excellent medium for showing refractions.

Refractive index is always greater than 1 since the light travels fastest in vacuum. For
glass, the range is between 1.4-1.7.

FORENSIC SCIENCE PAPER No.7: Criminalistics And Forensic Physics

MODULE No.21: Refractive Index Measurement for Glass
Samples - Part 1
 Refractive index measurement is affected by types of glass according to its color,
manufacturer and thickness.

The refractive index of several glasses is given below:

Head light glass – 1.47 – 1.49

Television glass - 1.49 – 1.51
Window glass - 1.51 – 1.52
Bottle glass - 1.52 – 1.52
Ophthalmic lens - 1.52 – 1.53
Common flat glass –1.51 – 1.53

Temperature, T and wavelength,  of light influence the refractive index of glass.

Temperature affects density; density further affects velocity of light beam as it passes
through the sample.
n 1/T

and

n 1/

Thus, refractive index thus gives an indication of the composition and the thermal history
of glass. By thermal history, we mean the last set of conditions under which a glass has
been cooled from its softened state.

Refractive index is the most commonly measured property as

 Precise refractive indices can be measured rapidly on the small fragments found
in a case work.
 Aids in the characterization of glass
 Provides good discrimination potential.

It is possible to determine the refractive index of very small glass fragments also which
can be found on the crime scene.

FORENSIC SCIENCE PAPER No.7: Criminalistics And Forensic Physics

MODULE No.21: Refractive Index Measurement for Glass
Samples - Part 1
 4. Pre-requisite for refractive index measurements
 Material recovered should be examined to determine if it is glass and then prepare
for another analysis.
 Glass fragments may be crushed to produce sharp edges using a mortar and pestle
or a glass crusher.
 Slides and cover strips should be cleaned prior to use with the help of solvents
such as acetone, ethanol or methanol and a lint free wipe, thus making sure that
the solvent has evaporated before mounting the samples.
 Since refractive index is a function of temperature, it is necessary to note down
the temperature also.

5. Different instruments used for refractive index measurements

There are a number of instruments to calculate the refractive index of glass fragments.
Some of them are as follows:

 Glass Refractive Index Machine (GRIM)

Glass Refractive Index Machine designed by Foster and Freeman, utilizes the oil
immersion/temperature variation method for the determination of the refractive index of
glass.

 Refractometer
It is a laboratory or field device for the measurement of refractive index using Snell’s
Law.

Main type of refractometer is Abbe refractometer. The only thing is that the methods
involving an Abbe refractometer requires pieces large enough to polish. It has got built in
thermometers and requires circulating water to cool the instrument and fluid temperature.

Dispersion can also be measured by Abbe Refractometer.

FORENSIC SCIENCE PAPER No.7: Criminalistics And Forensic Physics

MODULE No.21: Refractive Index Measurement for Glass
Samples - Part 1
  Hot stage microscope

It has a furnace with a heating element beneath and above the sample, which guarantees
outstanding temperature uniformity in the sample. In the method using hot stage
microscope, the glass sample is immersed in the high boiling liquid.

 Phase contrast microscope

Phase-contrast microscope is an interference microscope which converts phase shifts in

light passing through a transparent specimen to brightness changes in the image. Phase
shifts themselves are invisible but become visible when shown as brightness with
variation.

 Polarized light microscope

Polarized light microscope is a microscope equipped with two polarizing elements; one
of them is the polarizer which is located between the light source and the sample while
the other is analyzer which is located between the sample and the observer.

6. Different methods for calculating refractive index

It is not possible to measure refractive index directly as it is not possible to practically
measure the speed of light as it passes through the glass. Instead indirect methods are
used.

We can detect transparent objects in air such as glass fragments as they refract light.
Suppose two objects have got same refractive index, then it would be difficult to observe
any difference in the light that passed through them. If a piece of glass is immersed in a
liquid whose refractive index matches that of a glass, then the glass becomes invisible as
the light that passes through the glass would be same refractive index.

FORENSIC SCIENCE PAPER No.7: Criminalistics And Forensic Physics

MODULE No.21: Refractive Index Measurement for Glass
Samples - Part 1
 The various methods are based on this principle only. Some of the methods are as follows
in brief:

 Emmons Double variation method:

In this method, glass is immersed in oil. Here, a circular water bath is used to heat the oil,
with glass fragment immersed in it. In a way, this is a temperature variation method.

 Beckline method:
This is a method to determine refractive index of a transparent particle relative to its
surrounding medium. Its advantage is that it not only indicates the difference between the
refractive index and the liquid but it also indicates which possesses the higher value.

 Automated Glass Refractive Index Measurement:

This method is also temperature variation method but here glass sample is not immersed
in oil. The refractive index is calculated automatically from the data.

 Dispersion staining:
This technique is based on the principle of dispersion. Dispersion is the variation of
refractive index with the wavelength. Longer is the wavelength lesser is the refractive
index in comparison to light of small wavelength.

7. Summary
 The measurement of refractive index of glass actually gives an indication of the
composition and thermal history of glass.
 So, it actually becomes possible for the forensic scientist to know the make of the
glass fragments and can serve as a major evidence to solve the criminal case
under investigation.
 It is the process of refraction, which forms the basis of different methods for
determining the refractive index of the glass.
 We have also studied the methods and instruments used for determining refractive
index of the glass fragments in brief.

FORENSIC SCIENCE PAPER No.7: Criminalistics And Forensic Physics

MODULE No.21: Refractive Index Measurement for Glass
Samples - Part 1
 SUBJECT FORENSIC SCIENCE

Paper No. and Title PAPER No.7: Criminalistics and Forensic Physics

Module No. and Title MODULE No.22: Refractive Index Measurements-II

Module Tag FSC_P7_M22

FORENSIC SCIENCE PAPER No.7: Criminalistics And Forensic Physics

MODULE No.22: Refractive Index Measurements-II
 TABLE OF CONTENTS

1. Learning Outcomes

2. Introduction

3. Emmons Double Variation Method

4. Automated Refractive Index Measurement

5. Beckline Method

6. Dispersion Staining

7. Summary

FORENSIC SCIENCE PAPER No.7: Criminalistics And Forensic Physics

MODULE No.22: Refractive Index Measurements-II
 1. Learning Outcomes

In this module, you shall be able to learn about-

 The different methods of measuring the refractive index of the glass fragments in
details

2. Introduction

What we have understood till now is that one of the most important problems in forensic
glass analysis is the comparison between the known and unknown glass samples to
establish their origin. So various analyses is done. We have studied density measurements
till now.

This module is in continuation with the first part of refractive index module, in which we
had discussed the instruments used to measure the refractive index and the various
methods to determine the refractive index in brief.

This measurement hold importance in forensics as this gives a hint about the history and
the make of the glass and since it is not possible to measure refractive index directly, so
indirect methods are used. This is so because it is not possible to practically measure the
speed of light as it passes through the glass.

These indirect methods that we will discuss to determine the refractive index include
Emmons Double Variation method, Beckline method, Automated Glass Refractive Index
Measurement, Dispersion Staining. Most of these methods use the principle of refraction
and dispersion.

These are based on the fact that if these glass fragments under investigation have same
refractive index as the liquid in which it is immersed, then the glass fragments become
invisible.

FORENSIC SCIENCE PAPER No.7: Criminalistics And Forensic Physics

MODULE No.22: Refractive Index Measurements-II
 3. Emmons Double Variation Method

The most common and the oldest method to measure the refractive index of the glass had
been the Emmons double Variation method. This method was developed by Richard
Conrad Emmons at the University of Wisconsin Circa in 1928.

He found out that by manipulation of both the temperature and wavelength of light, it was
possible to obtain not only the refractive index of the glass but also how the refractive
index varies with the wavelength of the light.

In this method, the slide containing the glass fragments was immersed in silicon oil.
Here, the oil or the liquid was chosen in such a manner that the temperature coefficient of
the refractive index, dn/dT (Variation of refractive index with temperature) must be of the
order of 10-4. It must also be stable within the temperature range to be considered.

This slide with the liquid is then inserted into the hot stage and is illuminated using
monochromatic sodium light with the wavelength 5890 Armstrong. The temperature of
the hot stage could be controlled for heating and cooling with a precision of 0.2 degrees
Celsius or better.

For taking the observations a phase contrast microscope was used. (A Phase Contrast
Microscope as we have studied in the last module converts phase shift in light passing
through a transparent specimen to brightness changes in the image)

For noting down the observations, the Refractive Index of the oil was kept on changing
by varying the
(i) temperature of the oil mount and
(ii) wavelength of the light used

Until Beckeline disappeared and there was minimum contrast between glass and liquid
medium.

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MODULE No.22: Refractive Index Measurements-II
 The temperature at which Beckeline disappears is considered to be the match point at
which the refractive index of the glass equals the refractive index of the oil.

There are some advantages and some limitations of this method which are as follows:

Advantages:

 The wide variation in the Refractive Index of the oil reduces the number of oil
mounts needed. This is advantageous as the change in the oil involved can
damage the grain itself after the match point is obtained.
 This method provides a very rapid means of measuring the Refractive Index of
glass at multiple wavelengths.
 The precision of this experiment is almost from 0.00004 to 0.00006.

Limitation:

This method will not be able to actually differentiate between glass samples from
different sources with Refractive Index difference less than 0.0001.

4. Automated Refractive Index Measurement

Emmons Double variation method is still in use in some laboratories but it has been
almost completely replaced since the 1980s by an automated method referred to as
GRIM. It is known as Glass Refractive Index Machine due to the model name given by
the company which produces the instrument.

The Automated Determination of Refractive Index using oil immersion method along
with the phase contrast microscope and a video camera can be done for glass samples as
small as 300 micro grams and is called ASTM.

FORENSIC SCIENCE PAPER No.7: Criminalistics And Forensic Physics

MODULE No.22: Refractive Index Measurements-II
 In this method, the glass fragments should be cleaned with deionized water and ethanol,
then dried and crushed in very small pieces of glass of approximately 150micro meter in
size. A small sample is deposited on a slide and immersed in a micro drop of oil and
covered with a cover slip. In this method also the selected immersion oil/liquid should
have temperature coefficient of the order of 10-4. Also, the oil must be stable across the
temperature range under consideration.
The slide is put in the hot stage. Here the temperature of the hot stage is controlled by
GRIM fitted with a contrast microscope and a video camera. The temperature of the glass
is changed in a controlled manner by using the hot stage.

The temperature at which the glass disappears that is there is a minimum contrast
between the oil and the glass is recorded electronically and an average of the match from
both the heating and cooling cycle is converted to Refractive Index value according to the
calibration curve of the oil.

In details this means, the temperature of the hot stage is adjusted in such a manner that
the refractive index of the liquid is initially higher than the sample. But during the
analysis, the instrument lowers down the temperature of the preparation or the hot stage
through the match point for the glass. The contrast between the glass fragments and the
liquid is then observed and monitored and then the matching point is noted down. This
procedure is then repeated as the temperature is now raised through the match point.
These values are then recorded as the match temperature on cooling and the match
temperature on heating which are then averaged to give match point temperature of the
sample.

This is as discussed earlier is converted to the Refractive Index value according to the
calibration curve. The calibration curve has been obtained by standardization of oils
using reference glass with certified values of the Refractive Index. ASTM recommends a
minimum of three standard glasses for the calibration of each oil.

FORENSIC SCIENCE PAPER No.7: Criminalistics And Forensic Physics

MODULE No.22: Refractive Index Measurements-II
 The following are the advantages and some limitations of this method.

Advantages:

 The Automated Method for the measurement of Refractive Index has the
advantage of improved precision as well as improved accuracy.
 The Refractive Index is automatically generated and electronically recorded. Over
the years GRIM 1 has been replaced by GRIM 2 and now GRIM 3 is the latest
available.

Limitations:

 The hot stage, the glass slides and the microscope must be kept very clean. Traces
of liquid transferred from glass slides to the inner surface of the hot stage can give
anomalous results.
 This method will not differentiate between glasses with Refractive Index
difference of less than 0.00003.

5. Beckeline Method

Beckeline method is a method for determining the Refractive Index of a transparent

particle relative to its surrounding medium. The advantage of this method is that it not
only indicates the difference between the Refractive Index of the glass and the liquid but
also indicates which possesses the higher value.

We know that when an object is immersed in a liquid, a bright fringe called Beckeline is
observed at the object interface.

The glass fragment under investigation is immersed in a known Refractive Index liquid.
The difference between the Refractive Index of the glass fragment relative to the liquid is
observed.

FORENSIC SCIENCE PAPER No.7: Criminalistics And Forensic Physics

MODULE No.22: Refractive Index Measurements-II
 In this method, a bright halo or a Beckeline is observed. The movement of this Beckeline
with respect to the object/fragment on changing the focus of the microscope indicates the
Refractive Index of the object relative to the immersion oil, that is, whether the
Refractive Index of the glass is greater than or less than that of the liquid.

The difference in the Refractive Index is indicated by the amount of contrast between the
glass and the immersion liquid.

The fragment is then removed, washed and placed in another liquid with a Refractive
Index closer to the match point.

This is repeated until the Refractive Index of the match point has been deduced, that is by
using a succession of liquids with different Refractive Indices, the Refractive Index of the
sample can be deduced.

The following are the advantages and limitations of this method:

Advantages:

 This method requires only a microscope, calibrated liquids, the means to calibrate
them that is a Refractometer.
 It helps in rapid sorting of very different glass sources.

Limitations:

 The accuracy of the Beckeline method is limited by the visibility of Beckeline.

Factors such as object roughness, object inhomogeneity and small object size
diminish the visibility of Beckeline and the accuracy of this technique.
 It actually becomes difficult to recover the glass fragment under investigation and
then to clean it properly between liquids. As a result, evidence can be easily lost
or liquids may get mixed up resulting in errors in the measured indices.

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MODULE No.22: Refractive Index Measurements-II
  Results can be reported with a certainty of 0.001. Thus, it does not form a good
discrimination between sources.
 The Refractive Index of the liquids can vary with the temperature of the liquid. So
the laboratory temperature is to be maintained at a fixed value else error can be
introduced in the system.

6. Dispersion Staining

By dispersion, we mean the splitting of visible light into its different colors. This is
because of the fact that different colors bend with different refracting angles as they have
got different wavelengths.

Dispersion curve is the graph plotted between the changes in Refractive index to the
wavelength.

The dispersion staining method is based on the principle of dispersion. It is an analytical

technique that takes advantage of the differences in the dispersion curve of the Refractive
Index of an unknown material relative to a standard material with a known dispersion
curve to identify the unknown sample. These differences become manifest as a color
when two dispersion curves will intersect for some visible wavelength. It is a optical
staining technique and does not require any dyes or stains to produce the color.

When the conditions for dispersion staining are met, that is once the glass is mounted in a
liquid with a matching Refractive Index in the visible range but with a very different
Refractive Index, then the glass has a high refractive Index in the red part of the spectrum
and a lower in blue. Liquids tend to have a steeper dispersion curve.

The dispersion staining color is converted into a Refractive Index value that is added or
subtracted to the Refractive Index value of the glass standardized to obtain the Refractive
Index of the liquid.

FORENSIC SCIENCE PAPER No.7: Criminalistics And Forensic Physics

MODULE No.22: Refractive Index Measurements-II
 Dispersion technique being an optical effect and not involving a chemical reaction, so it
can be widely used in the study of everything from dental caries to hazardous material
identification. The most common application is the analysis of asbestos fibers but it has
many other very useful applications.

There are five types of dispersion staining technique or in other words, there are five
different optical configuration for the microscope used for dispersion staining. These
configurations are the following:

 Beckeline dispersion staining

 Oblique illumination dispersion staining
 Dark field dispersion staining
 Objective stop dispersion staining
 Phase contrast dispersion staining

Each configuration has its own advantages and disadvantages. Out of these techniques,
Beckeline dispersion staining and Oblique illumination dispersion staining were first
reported in the United States first by F. E. Wright in 1911.
All these have same requirements for the preparation of the sample to be examined.
Firstly, the glass sample under question should be cleaned and should be in proper
contact with the known reference material. In other words, the clean glass sample should
be mounted in a reference liquid. Dispersion colors will only be present if the two
materials have the same Refractive Index for some wavelength in the visible spectrum
but have different dispersion curves for the refractive index as discussed earlier.
A brief sketch of all these dispersion staining technique is as follows:

FORENSIC SCIENCE PAPER No.7: Criminalistics And Forensic Physics

MODULE No.22: Refractive Index Measurements-II
 Beckeline Dispersion Staining
This method is based on the fact that the particles behave like lens when immersed in a
liquid as they tend to be thinner at the edges than at the center. If the Refractive Index of
the particle is greater than that of the surrounding liquid, then it behaves like a convex
lens and will focus a parallel beam of light on the side opposite to the source of light.
This, under the microscope is seen as a bright ring of light, called Beckeline and moves in
from the edge as the particle is dropped out of focus by increasing the distance between
the stage of the microscope and the objective. If the stage is further moved closer to the
object then the particle will behave as a magnifying glass and the magnified image of
Beckeline appears outside the particle.
So the most important requirement for this method is that the incoming beam of light
should be made parallel. As we have already discussed, once the conditions for
dispersion are met, then the particle has the refractive index higher in the red part of the
spectrum while lower in the blue part. For the blue wavelength, the particle behaves like
a concave lens and the blue Beckeline moves out into the liquid.
The color of these two bands of light will vary depending upon the particle and the liquid
match in refractive index. For example, if the match is near the blue end of the spectrum
then Beckeline moving into particle contains the entire visible wavelength except blue
and will appear pale yellow whereas Beckeline moving out will appear dark blue. But, if
the match is near the red end of the spectrum then Beckeline moving into will appear
dark red while that moving out will be pale blue.
For larger particles, this is indeed one of the best methods as it is least sensitive to other
optical interferences.

FORENSIC SCIENCE PAPER No.7: Criminalistics And Forensic Physics

MODULE No.22: Refractive Index Measurements-II
 Oblique Illumination Dispersion Staining

In this technique, the beam of light illuminating the sample is made to fall at an oblique
angle through the sample. Although this will enhance the resolution of the structural
details in the particle oriented at right angles to the incident beam while some of the
resolution of features parallel to the direction of beam are lost. As a result of this
orientation of the beam, the relative refractive index of the particle and the surrounding
liquid becomes apparent.

So the wavelength for which the refractive index takes a higher value, are refracted into
the front lens of the objective from the side of the particle nearest to the side from which
the light is incident. Thus, if the particle has a high refractive index for all the visible
wavelengths, then this side will appear dark, while the side farthest from the source of
light will show all the wavelengths. These effects have a very sharp focus which is an
advantage over the Beckeline method as all the colors are more distinct in this method.

Dark-field Illumination Dispersion Staining

This type of dispersion staining is due to the image of the particle which is formed by the
refracted light while the direct light incident on the sample is oriented at such an angle
that it misses the front lens of the objective.

The result is that the background is black, while all the features of objects in the field of
view that don’t match the refractive index of the surrounding medium/liquid appears as
white. When a particle is mounted in a liquid that matches the refractive index within the
visible range of wavelength, then those are refracted by the particle and are thus, not
collected by the objective. So the image of the object is formed by the remaining
wavelengths. These wavelengths will combine to form a single color that can be used to
indicate which band of wavelength is missing. This method is more difficult to interpret
due to the single color.

FORENSIC SCIENCE PAPER No.7: Criminalistics And Forensic Physics

MODULE No.22: Refractive Index Measurements-II
 Phase Contrast Dispersion Staining

This technique will require a phase contrast objective. It takes into consideration the fact
that the rays of light that are not shifted in phase by the presence of the object are
separated from the light rays which are shifted in phase, at the back focal plane of the
objective.

These unaffected rays are significantly decreased in intensity. The particle will appear
colored from the contributing wavelengths for which the mounting medium has higher
refractive index.

Objective Stop Dispersion Staining

This type is based on the fact that all light unaltered by the presence of particles in the
field of view is focused at the back focal plane of the objective. This method enhances
the color effect but loses the resolution of the particles.

The following are the advantages and limitations of the dispersion staining technique:

Advantages:

 It has actually the same advantages as the Beckeline method, that is , it requires
only a microscope, calibrated liquid, refractometer and a dispersion staining
objective
 It also provides rapid sorting of different glasses.

Limitations:

 Extensive training in the use of dispersion staining is desirable for this technique,
since the reliability of the results is quite dependent on the skills of the analyst.
 In this technique also the results can be reported within a certainty only up to
0.001even under the very best conditions but are not much reliable also.

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MODULE No.22: Refractive Index Measurements-II
 7. Summary

In this module, we have studied-

 The various methods of determining the refractive index of the glass fragments
under investigation. This measurement makes it easy for the forensic investigators
to know the make of the glass, which can serve as important evidence against the
suspect.

 Since the Refractive Index cannot be measured directly as we know it is not

possible to practically measure the speed of light as it passes through the glass.
So, various indirect methods have been developed.

 These methods include Emmons Double Variation method, Automated Refractive

Index measurement, Beckeline method and the dispersion staining technique.

 All these methods are based on the principle of refraction and dispersion, that is
how light bends when it passes from one medium to another (either denser to rarer
or rarer to denser) and the splitting of light into its seven colors. In fact, there are
further five types of dispersion techniques.

FORENSIC SCIENCE PAPER No.7: Criminalistics And Forensic Physics

MODULE No.22: Refractive Index Measurements-II
 SUBJECT FORENSIC SCIENCE

Paper No. and Title PAPER No.7: Criminalistics and Forensic Physics

Module No. and Title MODULE No.23: Elemental Analysis of Glass

Module Tag FSC_P7_M23

FORENSIC SCIENCE PAPER No.7: Criminalistics & Forensic Physics

MODULE No.23: Elemental Analysis of Glass
 TABLE OF CONTENTS

1. Learning Outcomes

2. Introduction

3. Inductively Coupled Atomic Emission Spectroscopy

4. X Ray Diffraction Techniques for glass analysis

5. Raman and Infrared Spectroscopy

6. Summary

FORENSIC SCIENCE PAPER No.7: Criminalistics & Forensic Physics

MODULE No.23: Elemental Analysis of Glass
 1. Learning Outcomes
In this module, you shall be able to learn about-

 Significance and the use of elemental analysis of glass and

 The different techniques used for the analysis – Atomic emission spectroscopy,
X-ray Diffraction and Fluorescence methods, Raman and IR spectroscopy

2. Introduction
We know that glass samples are often found on crime scenes. As a result, a quickened
and a reliable glass origin determination is a huge and an important task in forensic
laboratories. Although Refractive Index typically performs glass fragment identification
but Refractive Index data overlaps itself and so often an additional information is
required for glass fragments.

The analysis of the elements present in the glass fragment under investigation can help in
determining the chemical composition of the glass fragment and can help to identify the
source of the fragment.

The concentration of certain elements in glass chemically characterize its source. In other
words, the chemical composition of different glasses is different, that is all glass products
display variations in the concentration of these elements and contain small concentration
of the trace elements. The concentration of most of the elements is controlled by the
manufacturer to impart some specific properties to a particular glass product. Thus, this
can be used to identify the product type of a recovered glass fragment.

But, even individual glass objects that have major element concentration , which are also
controlled by the manufacturer, will display visible changes and can give useful points
for a forensic comparison.

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MODULE No.23: Elemental Analysis of Glass
 Element concentration may be used to differentiate among glasses made by different
manufacturers or glasses from different product lines of the same manufacturer.

The wet chemical analysis of glasses is time consuming because of large amounts of
sample preparation, repetitive measurements, and manual work in general. So, alternate
methods are used. Some of these instrumental methods have been developed by forensic
scientists like Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP), X-ray
Diffraction (XRD), X-ray Florescence (XRF), Raman and Infra Red Spectroscopy.

Each of the observed and the measured values must be consistent between questioned and
known samples in order to prove same source. If any of the findings differ, then the
conclusion must be that, the questioned glass sample cannot be associated with the
known sample of the glass.

3. Inductively Coupled Plasma Atomic Emission spectroscopy

Before going into the details of this method, let us first consider a brief sketch of
spectroscopy.
By Spectroscopy, we mean the study of absorption and emission of light and other
radiation by matter. It includes the study of interactions between the particles such as
electron, proton, ions and with other particles as a function of their collision energy.

Inductively Coupled Plasma Atomic Emission Spectroscopy also known as Inductively

Coupled Plasma Optical Spectroscopy is an analytical method for the detection of trace
metals in the glass fragments. It is a type of emission spectroscopy that uses inductively
coupled plasma to dissociate the sample into its constituent atoms and ions. They return
to the ground state emitting electromagnetic radiation at wavelength characteristic of a
particular element.

Emission spectroscopy uses some means to excite the sample. After atoms or molecules
are excited, they relax to lower levels emitting radiation which is analyzed by means of a
suitable detector. When calibrated against the standard values, this technique provides a
quantitative analysis of the original sample. Inductively coupled plasma is a type of
plasma source in which the energy is supplied by electric currents which are produced by
electromagnetic induction that is by time varying magnetic fields.

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MODULE No.23: Elemental Analysis of Glass
 ICP-AES is the most common techniques for elemental analysis with which almost all
the dissolvable samples can be analyzed. This method of ICP is actually suitable for
dissolved glasses and is a rapid and precise method.

ICP-AES consists of two parts – ICP torch and the Optical Spectrometer. ICP torch
consists of three concentric quartz glass tubes with the output or the work coil of the
Radio Frequency generator surrounding this part of quartz. Here, Argon gas creates the
plasma.

Fig: ICP Torch

The moment the torch is turned on, an intense electromagnetic field is created within the
coil by the high power radio frequency signal which is further created by the Radio
Frequency generator.

The argon gas which flows through the torch is ignited with a Tesla unit that creates a
discharge arc through the argon to initiate this process, which is then switched off after
ignition.

The argon gas which is ionized in the intense electromagnetic field flows in a particular
pattern towards the magnetic field of the Radio Frequency coil. Thus, high temperature
plasma of almost about 7000 K is generated as a result of the inelastic collisions created
between the neutral argon atoms and the charged particles.

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MODULE No.23: Elemental Analysis of Glass
 The solid sample, dissolvable glass in the case of glass, is first dissolved and thus, mixed
in water. This sample solution is changed into an aerosol by an analytical nebulizer and
then directly introduced into the plasma flame.

The sample then collides with the electrons and charged ions in the plasma and the
sample itself breaks down into charged ions. The molecules breakup into their respective
atoms which keep on loosing electrons and recombine repeatedly in the plasma, thus
giving off radiation at the characteristic wavelengths of the elements involved.

In some designs, nitrogen gas or compressed air is used to cut the plasma at a specific
spot and transfer lenses are then used to focus the emitted light on a diffraction grating
which separates the light into its component wavelengths in an optical spectrometer.
While in some other designs the plasma is directly impinged upon an optical interface.

Fig: Atomic Emission Spectrometer

After the light separates into different wavelengths or colors, the light intensity is
measured by a photomultiplier tubes which are carefully positioned to view the specific
wavelengths for each element line involved. Thus, samples can be analyzed quickly. The
intensity of each line is then compared to the already measured intensities of known
concentration of the elements and their concentration is then computed.

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MODULE No.23: Elemental Analysis of Glass
 Thus, this process plays a very vital role in the elemental analysis of glass.

But the problem is that this process of ICP burns the sample so all the non-destructive
examinations should be complete.

4. X-Ray Diffraction and Fluorescence Techniques for Glass Analysis

X-Ray Diffraction and X-Ray Fluorescence techniques can be used both for elemental
analysis of glass and soil. X- Ray diffraction methods are specially significant for the
analysis of solid materials in the forensics. They are often the only methods that allow
further differentiation of materials under laboratory conditions. Minute contact traces,
small sample quantities can be easily analyzed. Let us consider these techniques in brief.

X-Ray Diffraction Technique:

We know that Forensic Science is actually based on the innovations and the latest
developments in the fields of science and technology, so any technique which will help in
the investigation of crime can be adopted for Forensic Science. One of the most
important part of forensics is the use of analytical techniques to uncover the fact from
even the smallest traces of evidence like very tiny glass fragments from the crime scene.
X-ray Diffraction and X-ray Fluorescence are such techniques that can be used to
characterize a wide variety of substances of forensic interests.

But, because of the form and size in which the crime samples exist, the amount of
material available and restrictions to preserve the sample, X-ray diffraction is rarely used
for the analysis of non-powdered samples.

The most important requirement for XRD technique is that the substance should be
crystalline up to a certain extent, that is, the atoms in the sample should be arranged in a
three dimensional periodic fashion. This is represented by crystallographic planes. X ray
diffraction actually occurs due to the scattering of X- rays from this set of planes
following the Bragg’s Law which is given as

2dsin= n

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MODULE No.23: Elemental Analysis of Glass
 Where, d is the distance between the planes, n is the order of diffraction,  is the angle of
diffraction or scattering and is the wavelength of the X Rays used.

Fig: X-Ray Diffraction

The most common method of X-Ray Diffraction is the Powder X-Ray Diffraction
method.

In this method a collimated monochromatic X – Ray beam is directed at the powdered

sample spread on a support. At least a few mg of sample is required. The sample holder is
able to rotate. The X-rays get scattered from the crystallographic planes of the sample.
XRD pattern is specific to a particular element or, in other words, each element gives out
its unique XRD pattern. So, it can be used as a signature of the material for comparison..
The intensities of the diffracted beam in this method are recorded by a detector fixed on a
movable carriage, which can also be rotated. The angular position is thus, measured in
terms of 2whereis the angle of diffraction.

Powder diffraction data are presented as a diffractogram in which the diffracted intensity
is shown as a function of the scattering angle, 2An instrument used for performing
powder measurements is the diffractometer.

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MODULE No.23: Elemental Analysis of Glass
 Relative to other methods of analysis, powder diffraction method is a rapid, non-
destructive analysis of multi component mixtures without any need for separation of
samples. This actually gives the laboratories an opportunity to quickly analyze the
unknown materials and perform material characterization in many fields including
Forensic Science. Identification is performed by comparison of the diffraction pattern
obtained to a known standard database such as the International Center for Diffraction
Data’s Powder Diffraction File.

Progress in the field of hardware and software has led to the manufacture of highly
improved and fast detectors which have actually improved the analytical capability of the
technique, relative to the speed of the analysis. Also, the high precision and accuracy in
the measurement of inter planar spacing, scaling down up to fractions of Angstrom,
results in an authoritative identification used in patents, criminal cases etc. this method
can also be used for amorphous materials also but as long as a suitable reference pattern
is known or can be constructed.

Fig: Diffractometer
Fig: XRF Spectrometer

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MODULE No.23: Elemental Analysis of Glass
 X-Ray Fluorescence:
XRF is a non-destructive technique used for chemical analysis of materials like glass and
soil in Forensics. The analysis is rapid and requires minimal or no sample preparation.

In this technique, an X-ray source is used to irradiate the specimen. As a result, the
ionization of the atoms take place that is one or more electrons may be ejected out of the
atom but the energy of the X-rays used to irradiate the sample should be more than the
ionization energy of the sample. These highly energetic rays are strong enough to remove
even the tightly bound atoms. After the electrons are removed, the electronic structure of
the atoms becomes unstable. As a result, the electrons from higher orbital jump to the
lower orbital. This causes the elements in the specimen to emit or fluoresce their
characteristic X-rays which are the secondary X-Rays. A detection system is used to
measure the peaks of the emitted X-Rays for qualitative or quantitative measurements of
the elements and their amounts. This emitted radiation is characteristic of the element
which actually helps in the identification of the element. The instrument used is the XRF
Spectrometer.

5. Raman and Infrared Spectroscopy

Before going into the glass analysis using Raman and Infrared Spectroscopy, let us first
have a brief introduction about Raman scattering or Raman Effect.

Raman Scattering or Raman Effect:

Raman Effect is the inelastic scattering (In such scattering, the kinetic energy of an
incident particle is not conserved. Some of the energy is either lost or increased) of a
photon discovered by C.V Raman. When photons are scattered from an atom or a
molecule, although most of the photons are scattered elastically (the scattered photons
have same frequency or wavelength as the incident photons) which is the Rayleigh’s
scattering, but a small fraction of the scattered photons are scattered by excitation, with
the scattered photons having frequency or wavelength different from the incident photon,
either higher than that or lower than that. This shift in the wavelength or frequency of the
photon is called the Raman Shift. The higher wavelength side is also called Stokes
Raman spectrum while the lower wavelength side is also called Anti Stokes Spectrum.

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MODULE No.23: Elemental Analysis of Glass
 Fig: Raman Spectrum

Raman and Infrared Spectroscopy:

Raman and Infrared Spectroscopy are the two spectroscopic techniques which can
produce very efficient and accurate detection of the pigments or color additives present in
the glass. In particular, Raman Spectroscopy analysis offers a very high discrimination
and match certainty, as Glass transmits a relatively broad Raman Spectrum due to the
color additives mixed into glass or organic protective layers used in car glass to prevent it
from breaking.

The use of Infrared Spectroscopy to determine the molecular structure had its roots
established in the nineteenth century, once, the Infrared region of electromagnetic
spectrum had been discovered by Sir William Hershel in 1800 while the Raman effect
was first observed experimentally only in 1928 by Sir C.V. Raman which resulted in
Nobel Prize in 1930.

In the past, the application of Infrared and Raman Spectroscopy to forensics had actually
been difficult due to the quantity of material that was required for the analysis and also in
most cases the destruction of the sample had to be done.

But, in 1970’s, the optical microscopes were coupled with spectroscopes to provide
characteristics identification data from spatially minimal regions of samples. So no
destruction or sample preparation was required. The first micro Infrared spectroscopy
appeared in 1960’s while micro Raman came into picture in 1976.

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MODULE No.23: Elemental Analysis of Glass
 Both the techniques are capable of recording data from particles even in pictogram range.
So, no destruction of sample is required. Despite of this, both the techniques have both
advantages and disadvantages which tell one or the other technique is preferred for
specific application. For example, the presence of water or hydrated chemical species in
specimens can hamper the mid-infrared analysis. While the optical dependence of Raman
Effect upon molecular polarizability rather than the dipole moment for the Infrared means
that the polar group such as –OH and C=O are better seen in the IR Spectrum whereas the
homo polar groups C=C or N=N are better seen in Raman Spectrum.

A major factor in Raman Spectroscopy application in Forensics is the ability to overcome

fluorescence emission and this needed the laser excitation at longer wavelengths from
visible to the near Infrared region of electromagnetic spectrum. So, now-a-days modern
spectroscopic laboratories in forensics have such laser sources as the samples may be
colored like the colored glass.

These techniques make possible the recording of the sealed sample contained in their
evidence bags seized at source and need not be opened in the analytical library.

The molecular fingerprint that is provided from the mid Infrared spectrum or Raman
spectrum is well characterized, so it becomes easy to differentiate between chemically
similar materials and not so in other cases.

Now let us consider a very simple and brief description of both the Infrared and Raman
Spectroscopy:

In Raman Spectroscopy, a monochromatic radiation of given wavelength, strikes the

sample (colored glass or other seized evidence) and gets scattered in all directions. Most
of the scattered radiation is elastic, but, some of it is changed in wavelength either
increased or decreased, called the Raman shift by an amount that corresponds to the
sample’s Raman active vibrational mode wavelength, v. The Raman shift can be positive
(v), Stokes lines or negative (v), Anti Stokes lines as shown in the figure above. In
this spectroscopy, it is the Stokes bands that are measured, since these have the higher
intensity and involve transitions from lower to higher energy vibrational levels. While
Anti stokes shifts occur as a consequence of a few molecules existing in an excited
vibrational energy level undergoing transition to lower energy level.

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MODULE No.23: Elemental Analysis of Glass
 In mid Infrared transmission set up case, the radiation from a broadband source
passing through a sample is absorbed by the IR active vibrational mode of wavelength,
v.

Both mid-IR and Raman spectroscopy are commonly used in microscopy based
configurations in which the vibrational spectrometer is interfaced with optical microscope
system, which enable both visual and spectroscopic examinations.

Out of the two, Raman spectroscopy offers some practical advantages over IR
spectroscopy as Raman spectroscopy is a scattering technique that uses a laser source and
so as such there is minimal requirement for sample preparation and presentation and so
the technique has a higher spatial resolution. But, still Raman spectroscopy is considered
to be less sensitivity technique in comparison to IR technique.

Since, colored glass are made from different materials so the Raman Effect that is the
Raman scattered band intensities and mid IR absorbance observed will be different for
different glasses and so a direct comparison with the existing data can be made.

Fig: Raman Spectrometer

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MODULE No.23: Elemental Analysis of Glass
 Fig: IR Spectrophotometer

6. Summary

 We have come to know that although Refractive Index typically performs glass
fragment identification but since Refractive Index data overlaps itself and so the
forensic investigators will require additional information for the glass fragments.

 The elemental analysis of glass fragments actually helps us in determining the

chemical composition of the glass fragments and will help to identify the source.
The concentration of certain elements in glass chemically characterizes its source.
It is controlled by the manufacturer which is done to impart some specific
properties to the glass.

 Since wet chemical analysis is time consuming so alternate techniques like

Atomic emission spectroscopy, XRD, XRF, Raman and IR spectroscopy have
been adopted for the elemental analysis of glass fragments.

 The only requirement for these techniques is that each of the observed and
measured values must be consistent between questioned and the known samples
in order to prove same source. If any of the findings differentiate, then the
conclusion must be that of the questioned glass sample cannot be associated with
the known sample.

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MODULE No.23: Elemental Analysis of Glass
 SUBJECT FORENSIC SCIENCE

Paper No. and Title PAPER No. 7: Criminalistics and Forensic Physics

Module No. and Title MODULE No.24: Soil and Paint Analysis

Module Tag FSC_P7_M24

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.24: Soil and Paint Analysis
 TABLE OF CONTENTS

1. Learning Outcomes

2. Introduction to soil analysis

3. Introduction to paint analysis

4. Various methods for soil analysis and comparison for different soil samples

5. Various methods for paint analysis

6. Summary

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.24: Soil and Paint Analysis
 1. Learning Outcomes
In this module, you shall be able to learn about-

 The methods for soil analysis and comparison of different soil samples
 The different techniques used for paint analysis

2. Introduction to soil analysis

Mud and loads of dust are sometimes found on vehicles or suspect’s shoes. Although soil
is quite different from other types of trace evidence, it still serves the same purpose. So,
here the basic question would be whether the soil came from the crime scene or not.

Although collecting soil sample from the shoes is easy but the choice of control sample is
difficult. This is due to the fact that soil is a dynamic accumulation of particles constantly
changing over very small distances. Soil sometimes varies within inches across the
landscape and within inches down into the ground. Primary known samples are chosen
from the spot where it is suggested the question sample originated such as location of
shoes, tire prints etc.

A thorough analysis is required to determine whether the two soil samples have the same
origin or not. So for this, methods like density gradient and observations of physical
characteristics is used.

3. Introduction to paint analysis

For the paint analysis, there are certain main concerns to be taken care of:
 Type of case or investigation
 Sample size
 Environmental effects
 Complexity and condition
 Collection methods etc

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MODULE No.24: Soil and Paint Analysis
 These factors actually guide the forensic examiners to choose different methods for
analysis for each specific case.

Moreover, paint films are characterized by various physical and chemical properties.
Physical properties include the color, layer sequence and thickness, surface and layer
features and contaminants while the chemical properties include pigments, polymers and
additives. These features can be determined by various macroscopic, microscopic,
chemical and instrumental methods difference in appearance, layer size thickness etc can
exist even in samples of known origin. So, the absence of certain significant features of
an analysis may suggest that the paint samples are from common origin.

Once the sample for the paint analysis is recognized, it is then removed manually with the
help of various lifting methods and cutting. Then, the analysis for the paint sample is
done taking into consideration that the methods used should be more specific and less
destructive rather than considering methods that require more sample preparation or
consumption. These techniques include Pyrolysis Gas Chromatography, Scanning
electron Microscopy-energy dispersive X-ray analysis (SEM-EDX), X-ray Fluorescence
and X-Ray Diffraction.

4. Methods for soil analysis and comparison of soil samples

In order to find a link between a suspect and the crime scene, the forensic investigators
most of the time find it beneficial to compare soil samples found o the crime scene with
the sample on the suspect’s clothes, shoes, house etc. for this a thorough analysis is
required to determine whether the two samples have same origin or source.

The various methods for soil analysis are the following:

Density Gradient Method

In this method, a cylinder is filled with various solutions in such a manner that at the
bottom is the solution with highest density while at the top is the solution with lowest
density and in between the density gradually decreases from bottom to top.

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MODULE No.24: Soil and Paint Analysis
 The soil sample is then placed in the cylinder. The soil will sink through the solution with
higher density until it reaches the place where its density matches with the density of the
solution. At this place, the soil particles will remain suspended and thus create bands in
the solution. The bands will represent the varying densities of the particles making the
soil.

Sample solutions from same origin will produce similar bands through this method. This
is due to the reason that the large deposits of soil have a uniform composition in regards
to percentage of various particles and density of each type of particle is always same as
the density is an intensive property. Thus, a sample that the forensic investigators collect
from the crime scene and a sample of soil found on the suspect’s clothing can be
compared by this method. If both the samples have same origin then they will certainly
show similar bands. But, if they show different bands then they are indeed from different
origin.

Fig.1: Bands created by various particles

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MODULE No.24: Soil and Paint Analysis
 Qualitative observation of physical properties

Soil samples can also be analyzed with the help of qualitative observations based on
sensory details and not mathematical calculations. In other words, the two samples can be
compared on the basis of color, texture, particle shape and mineral composition.

The color of the sample can be viewed simply with human eyes itself but both the
samples should be at the same moisture level as moisture can alter the color. For this, the
scientists usually heat the samples to dryness or add excess moisture to both the samples
so that their color can be compared accurately.

The texture of the soil depends on the ratio of sand, silt and clay which are based on
particle size and not chemical difference.

Regarding the shape, soil particles have angular, sub-rounded or well-rounded shapes.

Fig.2: Different shapes of soil particles

In order to examine on the basis of mineral composition, the forensic investigators use a
microscope to determine the make. This is quite a reliable method as color and shape of a
mineral is quite distinctive.

If all these physical properties match up then they have the same origin while if these
properties do not match then they don’t share a common origin.

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MODULE No.24: Soil and Paint Analysis
 4. Methods for paint analysis and comparison of paint samples

With the help of paint analysis, it is easier to identify the possible make, model and year
of manufacture of motor vehicles from the paint collected at the scene of crime or
accident. It is also possible to differentiate motor vehicle repaint from the original
equipment manufacture.

Once the evidence is recognized, try to remove it manually before tape lifts to collect
evidence. It is collected with tape lifts very carefully, being aware of the difficulty
encountered while manipulating paint samples bearing adhesive residues.

If the contact between any two coated surfaces is indicated, then there is a possibility of
cross transfers. As a result it is made sure that the samples from both the surfaces need to
be collected.

Paint flakes can be removed by a number of methods like lifting loosely attached flakes,
cutting samples of the entire paint layer structure using a clean knife or blade, dislodging
by gentle impacting the opposite side of the painted surface etc.

Once these formalities are complete, then for paint analysis, the sample size, condition
and layer structure complexity is to be considered while deciding as to which technique is
to be used. Also, it should be taken care of that more specific and less destructive tests
should be used

Samples which are neither restricted by amount and nor by condition should then be
analyzed in such a manner that the analysis will actually determine the color and texture
of the paint as well as the number, order, colors and textures of the layers in case the
sample is a multilayered sample.

Most of the time, instrumental techniques should be considered to analyze both the
pigment (a finely ground organic or inorganic, insoluble and dispersed particle) and
binder (a non-volatile portion or the liquid coating of a vehicle which serves to bind the
pigment together) in the paint sample.

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MODULE No.24: Soil and Paint Analysis
 The first step in the paint analysis is the visual and macroscopic evaluation, description
and documentation of the original condition of the sample.

The next step of the initial evaluation should start with a critical review of the chain of
custody, sealing of the package and identification markings of the sample. If the items are
found suitable for further evaluation, then a detailed accounting and description of the
paint fragments should be documented. That is, general condition, size, shape, exterior
colors etc. which is examined using stereomicroscope. For documentation written
description, sketches, photography should be used.

Some of the techniques used for a detailed paint analysis are the following:

Physical match:

Physical match is the most conclusive type of examination that a forensic investigator can
perform on paint samples. It involves the comparison of edges and surface striae between
samples. Both the edges and stria in question must possess unique characteristics. When
imaging methods are used to document a physical matching then the forensic examiner
should make sure that the method employed is dimensionally accurate and has associated
measuring scales. It should be made sure that the images are well-preserved and retained
as part of the documentation.

Micro chemical test:

These tests are used to discriminate between paint films of different pigment and binder
composition which are already similar in visual and macroscopical appearance. These are
based on pigment and binder color reactions with oxidizing, dehydrating or reducing
agents.

The problem with these tests is that they are destructive and should be applied to known
samples first, in order to know its efficiency. So, these tests should be used only in
situations in which the quantity of questioned sample is adequate.

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MODULE No.24: Soil and Paint Analysis
 These tests should be applied to both questioned and known samples concurrently. The
effect of these tests has to be recorded immediately. Reactions such as softening,
swelling, curling, color changes are some features which are to be noted. These results
are then primarily used for preliminary classification and comparison.

Polarized Light Microscopy (PLM):

This technique is used for examination of layer structure and also for the comparison and
identification of the particles present in a paint film including pigments, additives,
contaminants etc. It involves the use of polarized light. The basis of this technique is the
wave nature of light.

By polarized light we mean the following:

A light wave consists of crests and troughs which can be oriented vertically or
horizontally or any other plane. In other words, we can say the light particles vibrate in
all the directions. Such a light wave is called an unpolarized light. When this light is
passed through a Polaroid filter or a polarizer, the polarizer blocks the vibrations either in
vertical or in horizontal plane while permitting the passage of the remaining plane.

Polarized Light Microscopy is based on this fact of polarizing light. In Polarized

Microscope there are two filters, one is polarizer while the other is the analyzer. Light
from the source moves outwards towards the polarizer and then is analyzed at different
positions of the analyzer. That is, the two filters can be rotated in different positions
depending on which the spectrum will be formed. If the two filters are rotated in exact
opposition that is perpendicular to each other, then no image will be seen. Thus, with the
help of the second filter, different vibrational forms of light will pass through the
samples. The different appearance of how light behaves on impinging through different
samples of paint, is made use of, in determining the composition of the paint sample.

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MODULE No.24: Soil and Paint Analysis
 Fig.3: Polarized Light Microscope

Vibrational spectroscopy:

Infrared and Raman spectroscopy, the procedures for which have already been discussed
in the last module for elemental analysis, are used to obtain information about binders,
pigments and additives used in the coating materials.

 Infrared Spectroscopy

Since the paint fragments are small, so Fourier Transform Infrared Spectrometer is
recommended. Out of transmittance or reflectance techniques, it is the transmittance
technique is preferred as most of the binder, pigments have emission spectra.

In this type of spectroscopy, samples of individual layers is prepared using scalpels,

blades, forceps etc and placed on a salt plate or an appropriate mount.

 Raman Spectroscopy

This technique is based on scattering of light rather than the absorption unlike Infrared
Spectroscopy. So in this case, the results are totally complementary to those from
Infrared Spectroscopy.

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MODULE No.24: Soil and Paint Analysis
 Some paint samples may give rise to both Infrared absorption bands and Raman bands,
but their intensities will be different in both the techniques.

 Pyrolysis Gas Chromatography

This is a destructive method of chemical analysis in which the questioned paint sample is
heated to decomposition to smaller molecules which are then separated by gas
chromatography and detected using mass spectrometry. Here, pyrolysis means thermal
decomposition of materials in inert gases or vacuum. The sample is put in direct contact
with either a platinum wire or placed in a quartz tube and heated rapidly at 600 Deg Cel
to 1000 Degree Celsius. Large molecules then break at their weakest points and produce
smaller or more volatile fragments which are analyzed using mass spectrometry.

 Gas Chromatography

Chromatography is a laboratory technique used for separation of mixtures. In this, the

mixture is dissolved in a fluid called mobile phase, which carries it through a structure
holding another material called the stationary phase. The various constituents of the
mixture travel at different speeds, causing them to separate.

In the case of gas chromatography, the mobile phase is a carrier gas, most of the time an
inert gas such as Helium or an unreactive gas such as nitrogen, while the stationary phase
is the microscopic layer of liquid or a polymer but on an inert solid support, inside a piece
of glass or metal tube called a column. The instrument used for such a technique is gas
chromatograph.

 Mass spectrometry

Mass spectrometry is a very famous and powerful analytical technique used to quantify
known materials, to identify unknown compounds within a sample. The complete process
involves the conversion of the sample into gaseous ions, with or without fragmentation,
which are further characterized by their mass to charge ratios and relative abundance.

The applicability of this technique depends on the paint type, layer complexity and the
amount of sample consumption that can be tolerated.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.24: Soil and Paint Analysis
 Fig.4: Gas Chromatograph

 Scanning Electron Microscopy – Energy Dispersive X-Ray Analysis

This technique is used to characterize the morphology and elemental composition of paint
samples. In this process, an electron beam impinges over a selected area of the sample,
producing emission of various signals including X-rays, back scattered electrons or
secondary electrons. The emitted X-rays produce information regarding the presence of
specific elements, while electron signals produce compositional and topographical
visualization of sample.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.24: Soil and Paint Analysis
 Fig.5: Scanning Electron Microscope

 X-Ray Fluorescence and X-Ray Diffraction

These are both non-destructive techniques.

Because of the penetration depth of primary X-rays, X-Ray Fluorescence analysis yield
elemental data from several layers of a multilayered paint fragments simultaneously. This
analysis can be used qualitatively as variations in layer thickness cause variations in X-
ray ratios of elements present.

While X-Ray Diffraction technique is used for the identification of the crystal form of
pigments and not suitable for organic pigments. This technique is based on the emission
of characteristics X-rays after excitation of the sample by an X-ray source.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.24: Soil and Paint Analysis
 6. Summary

 Let us summarize what we have studied in this module. In this module, we have
studied about the soil analysis and paint analysis and their importance in forensic
investigation of a crime. For, this it is must to know how to collect and handle the
soil and paint sample.

 As far as soil sample is concerned, mud and dust can be found on suspect’s shoes
and on vehicles. Then to determine whether the known sample and the questioned
sample have same origin, methods like density gradient method and observation
of physical characteristics is considered.

 Coming to the paint analysis, forensic investigators should take notice of sample
size, environmental effects etc. Paint films are characterized by various physical
and chemical properties that include color, thickness, layer sequence, pigments,
additives etc. These can be determined by macroscopic, microscopic, instrumental
methods like pyrolysis gas chromatography, vibrational spectroscopy (infrared
and Raman spectroscopy) and scanning electron microscopy.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.24: Soil and Paint Analysis
 SUBJECT FORENSIC SCIENCE

Paper No. and Title PAPER No. 7: Criminalistics and Forensic Physics

Module No. and Title MODULE No.25: Fibres

Module Tag FSC_P7_M25

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.25: Fibres
 TABLE OF CONTENTS

1. Learning Outcomes

2. Introduction

3. Types of fibres

4. Significance of fibres as trace evidence in forensics

5. Collection of fibre evidence

6. Fibre analysis

7. Summary

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.25: Fibres
 1. Learning Outcomes
After studying this module, you shall be able to know about-

 The significance of fibres as trace evidence

 Different types of fibres
 Methods of collecting fibre samples from the crime scene
 Different methods for the analysis of fibres

2. Introduction
Fibres are thread like structures from fabric and other materials which are easily
identifiable under a microscope. The fibre examination can determine whether the fibres
are natural or manmade. Its source can be determined by comparing it with fibre from a
known source. Natural fibres are mainly from a plant or an animal source like cotton, silk
etc. while man-made fibres are made from synthetic materials like nylon, rayon etc. the
natural fibres can be easily detected by microscopy. But, most of the fibres used in the
garments are synthetic so accordingly various methods are used to analyze them. Fibre
examination is extremely useful in crime investigation as these are the trace evidence
which can be easily identified. A carpet’s fibre or from a person’s clothing can indicate
the individual’s presence on the crime scene. But, since fibres are very mobile and light
weight so they can easily get brushed off. So it becomes necessary to collect fibre
evidence on time to prevent loss of material or cross contamination.

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MODULE No.25: Fibres
 3. Types of fibres
Depending upon their source, fibres are broadly divided into two categories:

 Natural Fibres

Natural fibres are the oldest fibres known to us. Since these are made up of cells, they
have better ability to absorb moisture and are thus, considered to be very comfortable. So,
the clothing that directly touches our skin is mostly made up of natural fibres.

Natural fibres are further divided into two categories:

 Fibres from plant source

Examples are cotton, jute, linen etc.

Cotton fibres are commonly used in textile material. The type of cotton, fibre length, the
degree of twist contributes to the diversity of these fibres. The processing techniques and
color application also influence the value of cotton fibre identification.

Other fibres include jute; linen etc. the identification of less common plant fibre found on
the crime scene or on suspect’s clothing would certainly have increased significance.

Fig.1: Cotton fibres

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MODULE No.25: Fibres
 Fig.2: Jute

 Fibres from animal source

Animal fibres which are mostly used in textile materials is wool and the most common
wool fibres come from sheep. The end use of sheep’s wool indicates the fineness of
woolen fibres. The finer wool fibres are used in making clothing while coarser wool
fibres are used to make carpets. Thus, the diameter of the wool fibres holds importance in
the analysis of the fibre from the crime scene. Wool from Angora goat, camel are also
found. Other example for animal fibres is silk.

Fig.3: Types of wool

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MODULE No.25: Fibres
 Fig.4: Silk

 Synthetic or man-made fibres

These fibres are alternative to the natural fibres. More than 50 percent of the fibres are
man-made. They may be originated from natural materials like cotton and some from
synthetic materials like rayon. The most common examples of man-made fibres are
nylon, Dacron followed by acrylic etc. These are mostly used in garments, foam padding
and sound proofing etc.

Fig.5: Synthetic fibres

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MODULE No.25: Fibres
 4. Significance of fibres as trace evidence

Fibres are a form of trace evidence, which are small and easily transferable. These are
very useful in crime scene investigation as they can be easily identified under a
microscope easily.

There are actually several reasons for considering them as a crucial set of forensic
evidence:

 They are easily transferred from the clothing of a suspect to that of the victim.

 They are capable of multiple transfers. For example from carpet, bed etc to the
suspect’s clothing

 These transfers can be direct or indirect. By direct transfers, we mean that the
fibre is transferred directly from a fabric onto a victim’s body. While by indirect
transfer, we mean that the already transferred fibres on the clothing of a suspect
are transferred to a victim’s body.

 Fibres vary according to their end use.

 They exist in huge varieties.

A deep understanding of the direct and the indirect transfers is important while
reconstructing the crime.

Whenever two people come in contact with each other there may be transfer of fibres or
there may not be. But, the possibility of transfer is more. There are certain types of fabric
also that do not shed fibres very efficiently while some fabrics cannot hold fibres very
well. So, the construction and the fibre composition of the fabric, the duration and the
force of contact and the condition of the clothing with regard to the damage are important
considerations.

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MODULE No.25: Fibres
 Another important consideration is the time delay between the actual physical contact and
the collection of clothing items from the suspect or victim. If the victim is immobile, very
little fibre loss will be there whereas the suspect’s clothing will lose the transferred fibres
quickly. The possibility of finding transferred fibres on the clothing of the suspect a day
after the actual contact had been made will be very remote depending upon the use and
the handling of the of that clothing.

But, there are certain drawbacks also for considering fibres as trace evidence.

 It is actually hard to quantify the rarity of fibres as no real studies have been done.
 Moreover, class evidence does not lead to a specific person

5. Collection of fibre evidence

A carpet fibre or a person’s shoe can indicate the individual’s presence at a crime scene.
But, since the fibres are very mobile and light weight, they become airborne, get brushed
off easily or fall from clothing. This mobility actually makes timely crucial to prevent
loss of material or cross contamination. Although fibres can cling to each other or to hair,
they can still be easily brushed off. They can be collected from carpets, victim’s body,
victim’s clothing or suspected weapon.

Precautions while collecting the evidence:

 Photographs of all the evidence should be taken prior to collecting them

 Collect large items such as clothing in separate paper bags
 Do not keep suspect and victim items in direct contact with each other which can
lead to cross contamination.
 It should be made sure that the carpet, other materials that might have been
transferred to a suspect or a victim are all collected carefully.
 Bedding should be carefully handled to avoid the loss of evidence in the form of
fibres.

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MODULE No.25: Fibres
 Some of the common collection methods include individual fibre collection using
tweezers or vacuuming or by tape lifting:

 Visual collection

On most of the surfaces if not all, the fibres can be seen with naked eyes. Using clean
forceps and trace paper, then, the sample can be removed from the surface. It is then
placed on a clean piece of paper and is folded and packaged in a paper envelope or some
other packaging bag very carefully lest the evidence may get contaminated.

 Tape lifting

Water or methanol soluble tapes are available for the collection of fibre evidence. The
tape is applied to the location of the suspected sample, removed and then packaged.

 Vacuuming method

The area where the suspected samples are located are vacuumed in this technique and
then caught in a filtered trap attached to the vacuum. These samples are then packaged in
a clean trace paper to be submitted to the laboratory. Vacuuming is the least desirable of
these collection methods because there is always a risk of cross contamination if the
equipment is not cleaned properly between every use.

7. Fibre analysis

Fibre analysis is actually a method of identifying and examining fibres found from the
crime scene, used by the forensic investigators to procure crucial evidence during an
investigation.

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MODULE No.25: Fibres
 If a fibre exhibits the same microscopic and optical properties as a known fabric, the fibre
could have possibly originated from the fabric. Although, it is not possible to say that a
fibre originated from a particular fabric, fibre matches are not that insignificant. It is
actually because of many different types of fibres and fabrics and many method of
coloring them, the likelihood of finding coincidental matches is low. But, it is still
possible to say that a torn piece of fabric originated from another fabric if the torn edges
match.

There are certain crucial characteristics that make the examination and thus analysis of
the fibres easy. For example:

 Fibre diameter

The fibres vary in size from 10 to 50 micrometers.

The softer materials will have smallest fibres while the most durable materials will have
the largest fibres

 Fibre cross section

Basically, it is the cross section of the fibre that varies according to the type of the fibre.
The natural fibres have their origin from plants and animals and thus look rough at the
edges. This feature on the examination can actually reveal whether the fibre is natural or
man-made.

Also, for example, the finer woolen fibres are used for making clothing while the coarser
ones for using carpets. So again the size of the fibre can tell its origin.

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MODULE No.25: Fibres
  Fibre number

The number of fibres on the clothing of a victim can be identified as matching the
clothing of the suspect is important in determining the actual physical contact. The
greater will be the number of fibres; it is more likely that contact actually occurred
between these individuals.

 Fibre color

Fibre color actually influences the value of particular fibre identification. Often dyes are
used to give colors. Individual fibres may also be dyed before being spun into yarns.
Yarns can also be dyed and also fabrics made from yarns. Also, color cane be applied to
the surface of the fabric as found in printed fabrics. Thus, how color is applied and
absorbed along the length of the fibre are important comparison characteristics. Color
fading and discoloration can also lend increased value to a fabric association.

 Fibre location

Where fibres are located also affects the value given to a particular fibre association. The
location of fibres on different areas of the body or specific items at the crime scene
influences the significance of fibre association.

Based on the above discussed characteristics let us in brief consider some of the common
methods for fibre analysis. Fibre analysis does not actually follow any specific laid down
procedure. The most common use of fibre analysis is the microscopic examination of
both the longitudinal and cross sectional sample. Other methods include the burning and
solubility methods which are very less used. Fibre analysis is usually not done in
university labs because of the lack of required solvents.

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MODULE No.25: Fibres
 Apart from the visual examination of single fibre with a comparison microscope, some of
the methods for fibre examination are:

 Scanning electron microscopy

Scanning electron microscopy is a method of photography which requires an instrument

called scanning electron microscope. This type of microscope uses electrons rather than
light to form an image. There are many advantages of using SEM instead of light as it
allows a large amount of sample to be in focus at one time.

Fig. 6: SEM opened sample chamber

 Atomic force microscopy

Atomic force microscopy is a method which is carried out using an atomic force
microscope. It is an instrument to analyze and characterize samples at the microscopic
level. The instrument will allow an analyst to look at the surface characteristics with very
accurate resolution ranging from 100 micrometers to even less than 1 micrometer.

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MODULE No.25: Fibres
 Fig. 7: A commercial AFM set up

 Chemical or dye analysis

The chemical analysis will involve the extraction of the dye from the fibre sample and
then characterizing and identifying its chemical structure. It is actually difficult to extract
a dye from the fibre sample as these samples are typically small and it is also made sure
by the textile dyers that the dye stays in the fibre. This method of dye analysis is a
destructive method which leaves the fibre useless for further color examination. But, still
since some fibres have similar colors that chemical analysis becomes a necessity.

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MODULE No.25: Fibres
 7. Summary

Let us summarize what we have studied in this module. In this module, we have studied
about the types of fibres, its importance as trace evidence and its analysis.

 Fibres are thread like structures from fabric and other materials which are easily
identifiable under a microscope. The fibre examination can determine whether the
fibres are natural or manmade. Its source can be determined by comparing it with
fibre from a known source.

 Thus, we have studied that there are broadly two types of fibres : Natural fibres
are mainly from a plant or an animal source like cotton, silk etc while man-made
fibres are made from synthetic materials like nylon, rayon etc. the natural fibres
can be easily detected by microscopy. But, most of the fibres used in the garments
are synthetic so accordingly various methods are used to analyze them.

 Fibre examination is extremely useful in crime investigation as these are the trace
evidence which can be easily identified. But, they are very mobile and light
weight and can thus become airborne, get brushed off easily or fall from the
clothing. This makes the timely collection of the fibres from the crime scene very
crucial as next day there can be loss of evidence due to cross contamination also.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.25: Fibres
  A carpet’s fibre or from a person’s clothing can indicate the individual’s presence
on the crime scene. So, the fibres can be collected from the carpet, bed, victim’s
clothing etc. but, while collecting them lots of precautions had to be taken. Some
common collection method includes use of tweezers, tape lifting and vacuuming.

 Once the collection has been done, the evidence is packed very carefully while
taking for examination. Fibre examination can reveal whether the questioned fibre
belongs to the particular known fabric or not. Some of the common methods for
the fibre analysis include Scanning Electron Microcopy, Atomic Force
Microscopy, dye analysis etc. out of these dye analysis is done only when
required as it is a destructive method and thus one has to leave the possibility for
further color examination.

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MODULE No.25: Fibres
 SUBJECT FORENSIC SCIENCE

Paper No. and Title PAPER No.7: Criminalistics & Forensic Physics

Module No and Title MODULE No.26: Basic Principles of Photography

Module Tag FSC_P7_M26

FORENSIC SCIENCE PAPER No.7: Criminalistics & Forensic Physics

MODULE No.26 : Basic Principles of Photography
 TABLE OF CONTENTS

1. Learning Outcomes
2. Introduction: Photography
3. History of Camera & Photography
4. Light
4.1. Sources of Light
4.2. Colour Temperature
5. Terminology used in Photography
5.1. Film
5.2. Film Speed
5.3. Exposure
5.4. Aperture
5.5. Depth of Field
5.6. Shutter & Shutter Speed
6. Types of Camera
6.1. Analog Camera
6.2. Digital Camera
7. Types of Analog Cameras (Film Camera)

7.1 View Camera

7.2 Point and Shoot Camera

7.3 Twin Reflex Camera

7.4 Single Reflex Camera

FORENSIC SCIENCE PAPER No.7: Criminalistics & Forensic Physics

MODULE No.26 : Basic Principles of Photography
 1. Learning Outcomes
After studying this module, you shall be able to

• Learn History of Camera & Photography

• Understand Basic Principles of Photography
• Understand Terminology used in Photography
• Learn about different Types of Camera

2. Introduction : Photography
The word “Photography” comes from the Greek word (Photos = Light, Graphos =
Writing) meaning “Writing with Light”. The word camera is also derived from another
Greek word “Kamara” – meaning anything within an arched cover or enclosure. A room
is called „kamra‟ in Hindi. Photographic camera is a light tight box with light sensitive
material (film) at one end and a lens or pin-hole (to admit light) on the other end.

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MODULE No.26 : Basic Principles of Photography
 3. History of Camera & Photography

Mo-Tsu (China, approximately 500 B.C.) and Aristotle (Greece, 384 – 322 B.C.)
observed the formation of inverted image when light passed through a pin-hole and both
of them investigated independently.

A typical Camera Obscura at the beginning of the 19th century, somewhat larger than
the replica shown above, incorporates a mirror which reflects the image from the lens
onto a glass plate which holds a sheet of paper on which the image is being traced. The
double interlocking box enables precise focusing of the image.

At the beginning of the nineteenth century the first use of chemistry for Photography
was done by Thomas Wedgwood ; he made negative by placing a drawing (on glass) on
a paper previously treated with silver nitrate solution and finally exposing it to the
sunlight. He also tried to record image with Camera Obscurabut in vain, as silver nitrate
was not sensitive enough. His negative was not permanent.

William Henry Fox Talbot in 1835 independently produced a light sensitive paper by
bathing it first in common salt and when dried, in silver nitrate, together the chemicals
formed silver chloride. On this treated paper, he made contact prints of things like lace
and leaves – what we called photogram today and the prints were fixed in common salt
solution or with the solution of potassium iodide.

Talbot‟s photogram was, of course, negative but he soon evolved a method of reversing
them to form positive by printing them on to a second sheet of sensitized paper. Sir John
Herchel, (Talbot‟s friend) termed the first picture as negative and the reversed one as
positive it is the fundamental principal of modern photography. By the advice of Sir
Herchel, he adopted a more permanent way of fixing by using hypo-sulphite of soda to
wash out unexposed silver halide.

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MODULE No.26 : Basic Principles of Photography
 By using potassium bromide instead of common salt he made more sensitive emulsion. In
1840 he modified the process, which was first called Calotype and later Talbotype.

1826 – The first recorded

heliography, looking out of the
window into the yard, was
modified camera Obscura
(J N Niepce)

In 1847 collodian (a protection for wounds) was discovered, it was used as a base by
Archer in 1851, who exposed it in wet condition so it was called as Wet Collodian
Process. Charles Bannet, in 1878, used gelatin to form dry plate and it was the true
ancestor of film materials. In 1888 George Eastman first introduced Kodak Camera
which was laden in factory and developed in the factory after exposure. In 1889 Eastman
introduced to public the transparent celluloid film which could even be processed by the
amateurs.

Even with the passage of time various developmental work continued on paper, films,
photographic chemicals, lenses, cameras and other specialization related to the present
day modern photography – even when the digital photography have been evolved
surpassing the age old paper, film and chemical processes.

FORENSIC SCIENCE PAPER No.7: Criminalistics & Forensic Physics

MODULE No.26 : Basic Principles of Photography
 The first Kodak Camera with a celluloid film

Photograph has been described as „Printing with Light ‟. While a painter uses his brush to
create a picture, a photographer uses his camera plus the fact that Silver Nitrate turns
black on exposure to light.

The word „Camera‟ is derived from the Greek word „KAMARA‟ which means room. At
the beginning it was a light proof room or tent with a hole fitted with a lens and was used
by the painters to trace images by pencil on a canvas or a paper.

Later this principle was utilized to attain the principle of recording an image in a
photographic camera. But to retain its past form, some of the different discoveries were
utilized viz. 1614 Angelo Sola‟s finding of the property of Silver Nitrate turning dark
when exposed to sunlight; Joseph Prieslay‟s (1772) comprehensive description of
chemistry of light or chemicals in light and so on.

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MODULE No.26 : Basic Principles of Photography
 The camera works in much the same way as our eyes. The lens in the eye focuses the
image on the nerve cells in the retina at the back of the eye and this image is sent to the
brain by the optic nerves. Let us take a simple example – hold a pencil in front of your
eyes at about 2 feet distance. Objects away will appear out of focus. When you look
beyond the pencil to the far end of the room, it immediately comes into focus, the pencil
being blurred. The muscles of the eyes are acting on the lens, adjusting it so that the
image we are looking at is sharply focused on the back of the eyes.

After that the ancestor of our Camera came and it is a light tight box with the following
parts:-
i. A lens to produce an image.
ii. A fitting to hold a light sensitive film or plate.
iii. A focusing mechanism for subjects at different distance.
iv. Diaphragm: A metal sheet with hole kept in between the lens and photo-
sensitive plate so as to control the intensity of light.
v. Shutter: A mechanical device by which the light entering through the lens
is normally prevented from falling on the film but it can be displaced for a
certain span of time by some button so as to pass the light for certain
duration on the film for exposure.
vi. Viewfinder: It is a device to see the area being photographed. This is
how we can know the area being covered by the lens.

Let us understand light before understanding the parts of a camera because photography
is not possible without light:-

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MODULE No.26 : Basic Principles of Photography
 4. Light
Light is a form of energy which helps to see the objects in the material world around us,
that is, it is the link between the eyes and the viewed objects.

Visible light waves are the only waves we can see from the complete spectrum of the
electromagnetic waves. We see these light waves as the colors of the rainbow. Each color
of the rainbow has a particular wavelength. Red has the longest wavelength and violet
has the shortest wavelength among the seven colors of rainbow (VIBGYOR).
VIBGYOR is seen when the white light is split into its component colours when it passes
through a prism, this phenomenon is known as dispersion.

In the atmosphere, the formation of rainbow can be seen at times when water vapors act
as prism for the light that breaks apart wavelengths which creates a VIBGYOR. The
colours are as mentioned below like Violet, Indigo, Blue, Green, Yellow, Orange and
Red. Before violet there is an invisible ray called Ultra-Violet and after red the invisible
ray is called Infra-Red rays. These invisible rays can also be detected by photographic
plates/films.

A typical human eye can see light from 400 nm to 700 nm of the electromagnetic
spectrum. This range is called visible range. Not all colours that human eyes can
distinguish are in the visible spectrum such as brown, which is mix of multiple visible
spectrum colours.

Although photography is possible even in non-visible range of electromagnetic spectrum

such as in ultraviolet and infrared region, here we will only concentrate on photography
in visible spectrum region.

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MODULE No.26 : Basic Principles of Photography
 The wavelength of various colours of the visible spectrum is given in the table below, but
we will discuss wavelength of each color, in detail, one by one.

Colour Wavelength(nm)
Red 622-780

Orange 597-622

Yellow 577-597

Green 492-577

Blue 455-492

Violet 390-455

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MODULE No.26 : Basic Principles of Photography
 4.1 Sources of Light

In photography, two types of light sources are used namely

Natural light Artificial light

Sun Tungsten Bulb

Starlight Fluorescent Lamp

Volcano
Electronic Flash
Diya(Lamp)

LED Lamps

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MODULE No.26 : Basic Principles of Photography
 Bioluminescence

Studio Probe

Laser
Candle

From the chart, it becomes obvious that a natural light source comes from different
sources of nature on which we do not have any control. Their availability and location is
completely governed by nature. As a photographer one should only understand the
characteristic of the natural light and how to use it in the best way.

On the other hand artificial lights are manmade lights which are sometimes completely
under control and we have the freedom of choice how to use them either as a single
source or in a mixed way. Most forms of commercial/advertising, forensic, scientific
photography uses artificial light.

4.2 COLOUR TEMPERATURE

Colour Temperature can be explained as in simple terms as the colour an object produces
under different light sources. That means various natural and artificial light sources
produces different Colour temperature. This varies from red to blue. Candles, tungsten
bulbs and sunsets gives light which is close to red color (hence they give „warm‟ look to
the pictures), on the other hand clear blue skies gives a „cool‟ blue light.

Color temperature is generally recorded in Kelvin, which is the S.I. unit of absolute
temperature.

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MODULE No.26 : Basic Principles of Photography
 Cool colors like blue and white usually have color temperatures above 7000K, on the
other hand warmer colors like orange and red have color temperatures around the 2000K
mark.

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MODULE No.26 : Basic Principles of Photography
FORENSIC SCIENCE PAPER No.7: Criminalistics & Forensic Physics
MODULE No.26 : Basic Principles of Photography
 Photographic films are sensitive to Colour temperature. There are daylight type and
tungsten light type films available which gives natural Colour when exposed in respective
light sources. In digital cameras however we can control the Colour temperature through
White Balance setting and this will be discussed as we come to digital photography.

So, at different time of the day at different conditions we have different colours. Human
eyes are so highly developed that they cannot see the change, on the other hand brain
quickly adapts to the difference, but Colour films and recently the digital sensors cannot
adapt. As mentioned before, Colour films can only be set to one Colour temperature,
usually 5500°K which is the average Colour of a sunny day noon or 3200°K which is the
temperature of a sunny daylight.

5. Terminology used in Photography

5.1 Films
The heart of the film is a transparent plastic material (celluloid) called the base. The back
side of the film is generally shiny and has numerous coatings that are important for
physical handling and processing of the film.
The other side of the film is the sensitive side where the photochemistry happens. There
are 20 or more than 20 separate layers coated in the film that are mutually less than one
thousandth of an inch thick. Most of this thickness is consumed by a very special binder
called gelatin that grips the imaging components together.
Part of the layers which are coated on the transparent film don‟t form images. These
layers which don‟t form images are present to filter light, and to control the chemical
reaction which occurs in the corresponding steps. Sub-micron sized crystals of silver-
halide are there in the imaging layer, that act as photon detectors.
These crystals are supposed to be the heart of the photographic film, as they undergo a
photochemical reaction when exposed to various modes of electromagnetic radiations --
light.
Silver-halide grains are prepared by mixing silver-nitrate and halide salts (chloride,
bromide and iodide) in complex ways which results in a range of crystal sizes, shapes and
compositions. Then these undeveloped grains are chemically modified to increase their
light sensitivity.

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 To make these grains more sensitive towards blue, green and red light, organic molecules
known as Spectral Sensitizers are added on the surface of the grains. These molecules
adsorbs (attach) to the surface of the grain and transfers the energy from a red, green, or
blue photon to the silver-halide crystal as a photo-electron. Some other chemicals are
then added within the grains during its growth process, or added on the surface of the
grain. These chemicals affect the light sensitivity of the grain, known as its photographic
speed (ISO or ASA rating).
Generally there are three types of films:-

Black & White negative film Colour negative film Colour positive film
(transparency)

5.2 Film SPEED

Film speed is a unit to express the sensitivity of the films towards light. That means how
much amount of light is required by a particular film to give a standard exposure. More
sensitive film takes fewer amounts of light and time to create an image in a particular
lighting condition. The main units to express film speed are:
ASA – American Standard Association
ISO – International Standard Organization
DIN Deutsche Industries Norm.

Manufacturers all over the world usually make films as per Film Speed mentioned. Any
brand of film purchased from anywhere in the world of a particular film speed will
require the same amount of light to expose a particular subject in a particular light
condition.

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 More sensitive the film, less the amount of exposure is required for taking a photograph
and vice versa. More sensitive the film or higher the film speed, the picture becomes
more grainy and lower the film speed, sharper the picture.

Generally films are categorized as per their film speed as follows:-

Film 12 25 50 100 200 400 800 1600 3200

Speed Slow Speed Film Medium Speed High Speed Ultra High Speed
Film Film Film

The difference between slow and fast film is quality. Slow speed films usually produce
sharper and more detailed image while faster films have higher contrast and grains.

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 Film Speed is very important while calculating exposure of a photograph or the power of
an electronic flashgun. Earlier the camera exposure meter worked according to the film
speed setting of the camera. Once a film of a particular speed is loaded in a camera, all
the photographs are to be exposed calculating exposure according to that particular film
speed. Today in digital photography we can change the film speed or the sensitivity of the
sensor even for every frame just by pressing a button or a dial.

5.3 EXPOSURE

Exposure is the amount of light required to create a standard image on a photosensitive

medium of a given sensitivity. Exposure is the combined effect of light falling on the
photosensitive material i.e. the film and the sensitivity of the film (film speed).

The effect of the light falling on the film can be controlled by Aperture and Shutter
Speed. The sensitivity of the film is another controlling factor for the exposure which is
called Film Speed which has been explained in the last unit. So technically it is the joint
calculation of intensity of light and its duration.

5.4 APERTURE

Aperture is an opening in between or at the back of a lens which controls the amount of
light coming through it, it may be a fixed or variable.. Bigger the opening more the light
and smaller the opening less the light falling on the sensitive material. This is one of the
devices to control the exposure of the film or digital medium. It is expressed as “f”
number and every next bigger aperture gives double the amount of light.

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 Evaluation of the opening of the lens will vary the amount of light passing through the
lens. If we increase the aperture or reduce the f-stop number, more light will pass through
the lens. Every step towards higher F No: halves the light and every step towards smaller
F No: i.e. bigger hole doubles the amount of light. So if we take a photo with a bigger
aperture than required, more light will reach the photosensitive material and the
photograph will become brighter than a standard exposed image and if it is smaller, it will
become darker than normal.

Standard apertures are:-

f/64, f/32, f/22, f/16, f/11, f/8.0, f/5.6, f/4.0, f/2.8, f/2.0, f/1.8/f1.4

5.5 Depth of Field

One more thing that is intricately related to aperture is Depth of Field. Depth of Field
refers to how much of the picture is in focus. When we focus the camera lens to give a
sharp image of a particular subject, other objects closer or far away in the photo are going
to be out of focus if they are at a different distance from the focused subject. The decline
of the sharpness (for a particular „f‟ no.) of other objects is gradual. A shallow Depth of
Field means that only the subject is in focus while everything else is out of focus. A Deep
depth of Field means that everything is in focus. But for our practical purposes we select
a zone in front of and behind the focused subject so that the blur in this zone is too small
to be noticeable and can be accepted as sharp. This zone is called Depth of Field.

So, the aperture also controls how much of the photo is in focus. If the aperture is small
then everything will be in focus, while a large aperture will make objects blurred, even
slightly far from the subject.

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 Here we can see an example of a large aperture e.g. f/5.6, bringing little into focus, and a
smaller aperture e.g. f/20, obtaining more Depth of Field.

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 5.6 Shutter and Shutter Speed

This is a part of a Camera which blocks or restricts the light from entering the film plane
and exposes the film. the mechanical or electromechanical system for controlling the
time during which light is allowed to reach the light sensitive material in a camera i.e.
film or digital sensor is known as Shutter. It consists of some means of covering the
image created by the lens, opening or uncovering for a pre-determined duration of time
and covering it again. It can be activated by releasing the shutter release button. There are
mainly two types of shutter, a) Diaphragm or Leaf Shutter & b) Focal Plane Shutter.

Diaphragm or Leaf Shutter was devised by Mr. Friedrich Deckel of Germany in 1912.
This type consists of 3 to 5 metal blades which can open outwards leaving a clear hole for
exposure and covers again after a preset time. The speed is controlled by penions and
leavers. This type is generally mounted in between the lens components.

William England in 1861 invented the Focal Plane Shutter. It consists of one or more
roller blinds of fabric or metal, having a generally variable slit which moves across,
inside back of the camera just before the film or the sensitive material when the release is
pressed. It may move up & down or across from left to right or vice versa. When
exposure time begins, the first curtain is released to start its travel.

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 As it moves, the first curtain passes across the film frame, allowing light to fall on the
film. When the first curtain has completed its travel, the frame is fully opened. When
exposure time ends, the second curtain is released to begin its travel and close off light to
the film.

Shutter Speed is the duration of time generally expressed in seconds, during which any
type of shutter remains fully open for exposure. This excludes the opening and closing
time which is considered to be negligible. Along with aperture, shutter speed indirectly
controls the light falling on the sensitive material. The standard shutter speeds are 1/2000,
1/1000, 1/500, 1/250, 1/125, 1/60, 1/30, 1/15, 1/8, 1/4, 1/2, 1 sec.

So, here also every shutter speed mentioned provides half the amount or duration of light
in relation to the speed to its right and double the amount or duration of light in relation
to the speed to its left. That means a shutter speed of 1/60 gives half-light as compared to
1/30 and double as compared to 1/125.

Fast Shutter Speed Slow Shutter Speed

Object is freezed Object is blurred

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 Therefore the correlation between shutter speed and aperture size is a direct
one. Since, aperture and shutter speed both of them controls the amount of light reaching
onto the film (let slip from mind about the elements of Depth of Field, action freezing or
movement) And since both doubles and reduce in a scale of one time (1X or 100%): It
means you can FREELY interchange the settings on shutter timing and lens opening for
respective effects and YET retaining your preferred exposure setting. This factor is
constant when we consider the film speed to be constant. Now let us see what will be the
standard exposures in some standard light conditions with different film speed settings;

Here we can see that as the light intensity is reducing (from morning daylight to overcast)
we are opening the aperture to the next bigger one thus allowing double the amount of
light. It is worth mentioning that we can increase or decrease the exposure as per the light
condition by either adjusting the aperture or the shutter speed or both.

Here we have changed the aperture for ISO 100, and for ISO 200 and 400 we have
adjusted the shutter speed. It has to be remembered that the camera exposure always help
us to find the correct exposure for the particular ISO setting in the camera.

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 Now let us find what complementary exposure is and how can it affect a particular
photograph.

Aperture f/1.4 f/2 f.2.8 f/4 f/5.6 f/8 f/11 f/16 f/22 f/32 f/64

Shutter 1/2 ¼ 1/8 1/15 1/30 1/60 1/125 1/250 1/500 1/1000 1/2000
Speed

In the above chart suppose for a particular film speed and in a particular light condition,
an exposure of f/11 and 1/125 sec is found to be perfect. Now if we change the aperture
to f/8 which means we are allowing one stop more or double the amount of light, to
maintain perfect exposure we have to reduce the light half by adjusting the shutter speed
to 1/250 sec. So f/8 & 1/250 is a complementary exposure to f/11 & 1/125 as both gives
same amount of light to the film.

Similarly the other pairs of same colour are also complementary exposure to the original
exposure in red and since all the pairs are giving the same amount of light, photographs
exposed with all the pairs should be same. But it is not so in actual condition. This is
because photographs taken with wider aperture such as f/2.8 will have shallow or less
depth of field thus causing unsharp image while images taken with faster shutter speed
will freeze object movement in the frame.

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 So understanding and setting exposure, according to requirement is very important for
taking photographs. Sometime exposure compensation is also used to take intentional
under or overexposed photographs for achieving a desired effect.

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 -2 -1 0 +1 +2

If the camera functions automatically, the Exposure Compensation lets you to lighten or
darken the photograph. To lighten a photograph, you increase the exposure; to darken a
photograph, you decrease the exposure. The amount you increase or decrease the
exposure is specified in "stops." For instance, increasing the exposure 1 stop, you indicate
+1 to open the aperture or slow down the shutter speed. It‟s easy to use exposure
compensation because you can preview your changes on the LCD monitor.

6. Types of camera

According to technology there are –

6.1 Film (Analog) Cameras, and

6.2 Digital Cameras.

Both kinds of cameras functions on same principles except the image capturing principles
and some few minor differences. Presently we will discuss about various kinds of film
cameras.

A film camera is made up of three basic elements:

1. Optical (the lens)

2. Chemical (the film)
3. Mechanical (the camera body)

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 7. Film Camera

Film cameras can be broadly classified into three types as per their size, mechanism,
utility:-

 View cameras
 Point & Shoot Cameras
 Twin Reflex Cameras (TLR)
 Single Reflex Cameras (SLR)
 Specialty Cameras

Let us study each of them in detail:-

7.1 View Cameras

View Cameras or Large Format Cameras --

View cameras are built like an accordion, with a lens in the front, a viewing screen in the
back and flexible bellows in between. The film used in these cameras are quite large with
sizes ranging from 4x5”, 5x7” or even 8x10”. These cameras give sharp details and what
we see in the viewfinder is exactly what we get on the negative. In these cameras we can
change the position of the lens and the film relative to each other to correct distortion.

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 View cameras are bulky and must be used on tripods. We have to use black focusing
cloth at the back as the image on the viewfinder is not so bright and appears reversed
and upside down. Rapid set up and shooting with these cameras are difficult. These
are normally used for commercial studio photography, landscapes and architectural
photography.

7.2 Point and Shoot Cameras (P&S)

The viewfinder provides a rough idea of what is in view, but not the real image. These
cameras are easy to handle with simple features.

P&S Cameras can be categorized into two types: Compact and Rangefinder cameras.
Compact Cameras

A camera, as small/compact as possible, with built-in features such as automatic

exposure, flash, auto or fix focus, easy film loading & film advance for easy picture
taking can be described as a Compact or Point & Shoot Camera.

Some type of compact cameras have a fix-focus lens, but most of the compact cameras
have auto focus feature, though some of them have zone-auto focus, which means that the
focusing distance from infinity to close-focus will be step by step in a few stages only.
More advanced 35mm cameras have some control over focus and exposure. Focusing
mechanisms ranges from guessing at the distance and setting the lens to sophisticated
autofocus units.
Most of these 35mm cameras have a viewfinder that does not keep an eye out through the
lens. This leads to two problems. Firstly, we may not be able to see exactly what the film
sees due to parallax, this is a particular problem for close ups.

The second problem only happens with the cameras whose lenses have a zoom feature;
unless the viewfinder is fairly sophisticated, you will not see the effect of zooming.
Many of these cameras are small, light, and weather or waterproof. They make good

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 backup cameras or cameras to carry into places you just don't want to carry a bigger
camera. Without the zoom feature, they are more suitable for scenic picture capturing.

Rangefinder Cameras

These cameras are called "rangefinder" cameras because they focus using a dual-image
range finding device. Turning the focusing ring superimposes two images in a line to give
perfect focus. While using a rangefinder camera, the user never look through the lens but
focuses and composes through a window, which is present on the top right, just like on a
disposable camera.

A. Beam splitter
(semitransparent
mirror)
B. Light-gathering window
C. Frame lines
projection/parallax
compensation unit
D. Frame lines projection
semitransparent mirror
E. Rotating
mirror/pentaprism
F. Viewfinder
G. Viewfinder frame
H. Static Image
I. Secondary Image

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 Rangefinder cameras differ from the SLR‟s remarkably as they do not make use
Through-the-Lens (TTL) viewing and focusing, although most modern Rangefinder
cameras have TTL metering. Instead, focusing in Rangefinder cameras are executed via a
rangefinder mechanism that can be either coincident (“classic” rangefinders) or
electronic.

The accuracy of focusing depends on the effective base length, which in case of RF
cameras is derived from physical distance between beam splitter and rangefinder
mirror/pentaprism (see diagram above) multiplied by the magnification of the viewfinder.
The larger and effective base length, the more accurate the rangefinder is.

The middle rectangular window just above and to the right of the lens on most of the
rangefinder cameras collects light to make the frame lines brighter. Beam splitter (A) and
rotating mirror/pentaprism (E) form two images in the viewfinder – static (H) (through
the beam-splitting mirror) and secondary (I) (through the rotating mirror). The lens is
linked with the (E) via moving camera at the lens‟s base, therefore while rotating the
focusing barrel one sees the secondary image moving across the viewfinder. When static
and secondary images match the focus is achieved.
Focus control for optical coincident-type rangefinders
Out-of-focus In focus
(no match of overlay image) (overlay image matches)

Advantages of Rangefinder Cameras

The image quality of Rangefinder cameras is good because there is no flipping mirror.
As flipping mirror is not present in it, so there is much less vibration to blur hand-held
images. At speeds of 1/30 to 1/8, the flipping mirrors of SLRs often gives blurred images
made from tripods unless a mirror lock-up is used.

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 Rangefinder cameras have accurate focusing for wide and normal lenses. Rangefinder
works well without the extra weight of prisms focus screens and flipping reflex mirrors.
As SLR mirrors flip up to take a picture, its viewfinders goes black at the most important
point: the point at which an image is recorded forever.

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 Rangefinder cameras viewfinders never black out, so you always know the subject's
expression as it is recorded, especially with flash. While using a rangefinder, you press
the button, and it goes. You have captured the peak of the moment, forever. But while
using an SLR, the mirror has to get out of the way before the shutter can open up. But by
the time the SLR‟s mirror gets out of the way, your conclusive capturing moment is gone.

Disadvantages of Rangefinder Cameras

The major disadvantage of Rangefinder camera is that we never come to know what we
are getting with rangefinder cameras as the viewfinder is separate, and it sees from a
different point of view. For regular shots at regular distances, this is not important, but for
the long lenses and major use, rangefinders give us no clue to what we are capturing.
Even with a LEICA rangefinder, we never really know what has been exposed until the
final image is printed. We never come to know or any hint of Depth of Field with a
rangefinder camera, in whose viewfinders everything is always in perfect focus. With a
rangefinder camera and a long lens, we're usually looking at only a small cut-out frame in
the finder.

7.3 Twin Lens Reflex Cameras (TLR)

A twin-lens reflex camera (TLR) is a type of camera with two objective lenses of the
same focal length. One of the objective lens is the photographic (lens which takes the
photograph), while the other lens is used for the waist-level viewfinder system. In
addition to the objective, the viewfinder comprises of a 45-degree mirror (the reason for
the word reflex in the name), a matte focusing screen at the top of the camera, and a pop-
up hood surrounding it. The two objective lenses are connected, so that the focus shown
on the focusing screen will be exactly the same as on the film. However, many low-
priced TLRs have fixed-focus models. Most of the TLRs use leaf shutters with shutter
speeds up to 1/500th sec with a B setting. For practical purposes, all TLRs are film
cameras, most often using 120 films, although there are many cameras with other
formats. Expensive TLRs have a pop-up magnifying glass to assist the user in focusing
the camera. In addition to that, many have a "sports finder" consisting of a square hole
punched in the back of the pop-up hood, and a knock-out in the front.

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 7.4 Single Lens Reflex Cameras (SLR)

Single-lens reflex cameras or SLR‟s are more complex form of cameras, than any other
types of camera. The viewfinders of other camera types are quite simple and usually have
nothing to do with the main lens of the camera.

In basic types the viewfinder is just a rectangular-shaped hole and in more complex types
the viewfinder is somehow connected to the main lens for focusing purposes (twin-lens
reflex (TLR) cameras for example), but still these systems are simpler than SLR cameras.
So, how does a SLR camera work or what makes it so complex? The key parts for the
light to move through the camera are: lens, mirror, focusing screen, prism and eye piece.

The lens is made up of several optical elements to form the image on the film. The mirror
is small, light and capable of moving up and down. Focusing screen is made up of ground
glass and when image is projected on it, the image becomes visible and doesn‟t just go
through as with regular glass. Sometimes the focusing screen also has some features that
will help us focus the picture.

The prism (its shape may vary, but the idea remains the same) is made up of glass and it
reflects the image from the focusing screen to the eye piece, which itself is just a piece of
glass or simple lens, that we are looking through.

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 The red arrows are showing the path of light during the composing of the photo and the
green arrow showing the path after actually pressing the shutter release button for taking
the photograph. Mirror moves up, shutter opens up, shutter closes down and mirror
moves back down are the actions that take place on that photo taking process.

Have you noticed that when you are taking a photograph with a SLR camera, the
viewfinder goes black for a moment? That is the mirror in upper position closing the
focusing screen and preventing an extra light from getting through the eye piece while the
shutter is open.

As you can see, the image is mirrored. If there is another mirror instead of a prism, the
image in the viewfinder would be upside down. So, the prism mirrors turns the image
back straight. But still, if one mirror flips the image upside down and the second one
would turn it around again, the image would still be on its head? And actually, all images
on the film are also upside down as the last photo shows.

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 To control exposure in a SLR camera, one must know how to control the Shutter Speed,
Aperture and set the Exposure meter to find out the correct exposure. To start with
controlling Shutter Speed, there are both analog dials and digital display to set the
shutter speed as follows:

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 Similarly for controlling aperture, older cameras had aperture control on the lens ring
and the electronic cameras had aperture control from display window as follows:

The purpose and effect of controlling the aperture and shutter speed has already been
explained earlier and needless to say that these two are the major factors for controlling
the required exposure both in a film and a digital camera.

The light meter or exposure meter inside a camera both in an old SLR camera and the
latest camera helps us to achieve correct exposure and sometimes gives us automatic
exposure in the program or automatic modes. To make the exposure meter work correctly
we must set the film speed accordingly. Let us see how to set the film speed in a SLR
camera:

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 The film speed of a SLR camera can be set manually in the range of ISO 12 to 6400. This
calibrates the built in exposure/light meter to calculate the amount of light required for a
particular scene and help the photographer to determine exposure. Film speed of the
loaded film can also be known through the DX film cod reader in the chamber where the
35mm film is loaded in the camera.
When the exposure setting is proper or the
light is correct, the red bar is at the middle
showing correct exposure.

When the exposure setting is under or the light

is less, the red bar is at the (-) side showing
under exposure. Here we have to open
aperture or reduce/slow down the shutter
speed.

When the exposure setting is over or the light is

more, the red bar is at the (+) side showing
over exposure. Here we have to close aperture
or increase/ use fast shutter speed.

Metering system optics

There are three Auto Exposure (AE)
metering sensors in different locations
are used for the six metering modes. The
16-zone metering sensor above the
eyepiece is used for 16-zone Evaluative,
Partial, and Spot & Center-weighted
Average Metering. At the bottom of the
mirror box, a metering sensor is used for
Fine Spot Metering. At the bottom of the
mirror box, the three-zone TTL flash
exposure metering sensor is used for off-
the-film ("OTC") metering. Some
cameras have multi metering modes
including off-the-film flash metering. The
metering mode can be selected (Five
metering modes easily switchable) to suit
the user's objectives.

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 SUBJECT FORENSIC SCIENCE

Paper No. and Title PAPER No.7: Criminalistics & Forensic Physics

Module No. and Title MODULE No.27: Photographic Lenses, Filters and Artificial
Light
Module Tag FSC_P7_M27

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Artificial Light
 TABLE OF CONTENTS

1. Learning Outcomes
2. Introduction- Camera Lenses

i) Convex Lens
ii) Concave Lens

3. Useful terms of the lens

4. Types of Photographic Lens
5. Defects of Lens
6. Filters for Photography
7. Film Sensitivity
8. Colour of Light
9. Summary

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 1. Learning Outcomes
After studying this module, you shall be able to know –
 What are Camera Lenses and their types
 Various terms of the Lens
 Various types of Filters used in Photography

2. Introduction – Camera Lenses

Camera lens is a transparent medium (usually glass) bounded by one or more curved surfaces
(spherical, cylindrical or parabolic) all of whose centers are on a common axis. For
photographic lens the sides should be of spherical type. A simple or thin lens is a single piece of
glass whose axial thickness is less compared to its diameter whereas a compound lens consists of
several components or group of components, some of which may comprise of several elements
cemented together.

Lenses are mainly divided into two types, viz.

i) Convex Lens
ii) Concave Lens

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 i) Convex lens:

This type of lens is thicker at the central portion and thinner at the peripheral portion. It casts real
image and so can be used to take photographs. Convex lens can be divided into three types-

(i) Bi-Convex or Double Convex

(ii) Plano Convex
(iii) Concave Convex or Meniscus

ii) Concave Lens:

This type of lens is thicker at the peripheral portion and thinner at the centre. It cannot cast real
image, so a single concave lens cannot serve the purpose of photography. Like convex lens, this
type can be subdivided into three types-

(i) Bi-Concave or Double Concave

(ii) Plano Concave
(iii) Convexo Concave

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 In modern cameras, both negative and positive lenses are used but the net effect of the
combination should be positive.

3. Useful Terms of the Lens

1) Optical Centre
It is a point within the lens through which light passes undeviated or without changing the
travelling path.

2) Principle Axis
The axis passes through the optical centre of the lens which is horizontal when the lens is
placed vertical to the horizon. It is a stroke linking the centers of curvature of its surfaces.

3) Focus or Focal Point

When analogous beam of light passes through the positive lens (analogous to the
principle axis) then it converges at a point and it seems to diverge from a point in case of
a negative type lens. This point is known as focus.

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 4) Focal Length

The space between optical centre and focus is known as Focal Length. Focal length commonly
measured in millimeters (mm) and is the basic explanation of a photographic lens. Though it is
not a dimension of the actual length of a lens, but a calculation of an optical distance from the
point where light rays meet to form a sharp image of an object on the digital sensor or 35mm
film at the focal plane in the camera. The focal length of a lens is determined when the lens is
focused at infinity.

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 5) Focal Plane

The imaginary plane passing through the focus and perpendicular to the principle axis is known
as focal plane.

6) f-Number

It is defined as the ratio between the focal length and the diameter of the diaphragm. “f” number
= F/D where F= Focal Length and D=Diameter of the slit or diaphragm. The intensity of a lens is
given by an arrangement of focal length and its diameter. In case, if the focal length of any two
lenses is found to be identical then the lens having greater diameter will be brighter. In an
instance, the focal length is 50mm and the lens diameter is 17.8mm then, focal length divided by
lens diameter gives the lens a maximum F-stop of 2.8.

4. Types of Photographic Lens

Photographic lenses are divided into various categories according to their focal length, speciality
and use. Although modern compact cameras come with integrated lens with variable focal length
however, only SLR cameras have the advantage where one can change and use almost any type
of lens according to their requirement. The diagram below shows how change in focal length
determines the angle of view of the lens.

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 i. Normal Lens

The standard lens has a stable focal length (50mm, 85mm) and imitates exactly what the
human eye sees in terms of viewpoint and angle of view. For a 35mm film camera or a
full-frame DSLR, the 50mm lens is considered as standard.

ii. Wide Angle Lens

A wide-angle general has less focal length (10 mm 42mm) in relation to a standard lens.
This enables us to seize a relatively wider angle of view. A wide-angle lens is a natural
choice for capturing outdoor landscapes and group portraits. In fact, wide angle can be the
only way to capture the complete setting without omitting any important elements in the
image. In this manner, we can use wide-angle lenses to capture a deep Depth of Field.

iii. Telephoto Lens

Telephoto lenses (100mm - 800mm) provide a constricted field of view. These extended
lenses allow compression of distance (and constricting the sense of depth, also) and take
view of a particular object from distant. They have a good resolving power as well as an
inherent shallow DOF, where even the minor lateral movement can take a subject out of
focus.

iv. Zoom Lens

Zoom lenses are beneficial because they allow for an array of different focal lengths lacking the
necessity to transfer various prime (fixed focal length) lenses. This allows the photographer
to quickly zoom in and capture the shot, then zoom back for a wider angle. While this is a
wonderful advantage, there are optical limitations that should be understood when using a zoom
lens. Each lens possesses a maximum aperture or lens opening used for capturing the light. On
most zoom lenses, the maximum aperture can change as we zoom and the optics move to focus
at the fresh zoom setting. These zoom lenses are said to possess a "variable" aperture. To attain
the widest probable aperture, we are required to use widest zoom setting.

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 v. Close UP or Macro Lens

Close-up or Macro lenses are used for close-up or “macro” photography. The focal length
ranges between 50-200mm. These lenses accomplish razor-sharp focus for objects in the
macro focus distance, although they lose their capacity for sharp focus at far distance
objects. These lenses permit the photographer to achieve life-size or larger images of
subjects like wasps, butterflies, and flowers.

vi. Fish Eye Lens

A fisheye lens is a specialized, wide-angle lens that provides extremely wide images by
altering straight lines into curves. It occasionally forms circular, convex, or oval pictures
by altering the viewpoint and forming a 180° image. The range of focal length differs
from 7~16mm in a fish-eye lens.

vii. Tilt-Shift Lens

The Tilt-Shift lens permits us fluctuate the vanishing points. If you are firing buildings,
you can modify the perspective of an image so the parallel lines don’t converge, thus
eliminating the distorting quality of the lens. The tilt-shift lens also allows us to desirably
focus on an image where only particular parts of the image are in and out of focus inside
the same plane.

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 5. Defects of Lens

i. Spherical Aberration

Spherical Aberration is an optical complexity which arises when all inward light rays terminate
focusing at diverse points later passing through a spherical surface. Light rays passing through
a lens near its horizontal axis are refracted lesser than the rays nearer to the edge or “periphery”
of the lens and as a result, end up in different spots across the optical axis.

ii. Chromatic Aberration

Chromatic Aberration, also known as “color fringing” or “purple fringing”, is a common optical
problem that occurs when a lens is either unable to bring all wavelengths of color to the same
focal plane, and/or when wavelengths of color are focused at different positions in the focal
plane. Chromatic aberration is caused by lens dispersion, with different colors of light travelling
at different speeds while passing through a lens.

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 iii. Coma

Coma is an aberration which causes rays from an off-axis point of light in the object plane to
create a trailing "comet-like" blur directed away from the optic axis. A lens with considerable
coma may produce a sharp image in the center of the field, but become increasingly blurred
toward the edges.

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 iv. Astigmatism

Astigmatism (pointlessness) is a refractive error which occurs when a point sending light through
a lens cannot be projected as one point. It appears as a line on the focal plane. Another
explanation is that astigmatic lenses fail to represent horizontal lines in the vertical line form into
the same image plane. . This effect mainly appears when biconvex or biconcave lens elements
are used.

It has been observed that all lens defects can be minimized by combination of positive and
negative lens and modification of design and coating.

6. Filters for Photography

Filter is a device of glass or other material interposed between the scenes being photographed for
the purpose of deducting or eliminating certain colours, generally to which the film is most
sensitive also called a colour filter or optical filter. Generally, two types of filters available are
as follows:

i. Coloured Glass Filter

ii. Gelatin Dye – Sandwich filter.

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 There are five main types of filters as per their usage:-

a) Correction Filter:

This is used to correct the imperfect colour sensitivity of the film and make it translate the
subject into tones of grey, and the same brightness as the colours appear to the eye. It is also used
in the colour to achieve desired colour temperature.

Filters do not really enhance color, but only absorb various wavelengths to upsurge the relative
proportion. So the initial light source must have the colors in it which we want to start
with. Some sources which lack various wavelengths, will not be added back using only
filters. This is particularly true of many types of metal halide lighting. With other lighting
categories, such as fluorescent, color temperature quantities will not make available the correct
filter necessities subsequently color temperature theory is based on having a continuous
spectrum, meaning light at all wavelengths.

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 No Filter 85B = Cokin P30

b) Contrast Filter:

This is used to darken the reproduction of a certain colour for special effect. There are many
circumstances, such as bright sunlit exteriors, where proper contrast is difficult to
maintain. Exposing to highlights or darkness will leave the other under or over exposed. Low
Contrast filters create a less amount of "localized" flare near highlight areas within the
image. This reduces contrast by lightening close shadow parts, parting highlights almost
unaffected. Soft Contrast filters comprise a light absorbing component in the filter which, when
deprived of exposure compensation, will decrease contrast by darkening highlights too. Use this
latter filter when lighter shadows are not according to the need. In both cases, the mild flare
created from bright highlights is mostly used as a lighting effect.

c) Red Filters

Red filters forms strong effect and significantly enhanced contrast. They are generally
considered as too "harsh" for various types of photography, however can be used to create
remarkable creative effects.

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 d) Orange Filters

Orange filters falls between red and yellow filters. It forms a nice balance of each one's
properties.

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 e) Yellow Filters

Yellow filters produce the most subtle effect of the 5 coloured filters. In most of the cases,
difference is hardly evident, although it can help us to lift a photo.

f) Colour Compensation Filter:

Color compensating filter is used to make adjustments to the red, blue or green characteristics of
light. These are applied in correcting for color balance, light source variations, different reversal
film batches, and other color effects. They are available in density variations of Cyan, Magenta,
Yellow, as well as Red, Blue, and Green filters.

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 g) Special Purpose Filter:

It is used to take picture by the light of a single colour only. These are mainly used for
scientific, aerial and other special photography (as telephotography in infra-red).

h) Infra-Red Filters :

In special circumstances, we use black-and-white or color infra-red sensitive films. For

aerial haze penetration, recording heat effects, and forensic photography, they are invaluable.
Their color and tonal renditions are very diverse, though; from other film types (refer film
producers for further details). Various filters are used to diminish undesirable visible
light. Red, orange, and yellow filters used for panchromatic black-and-white film, can
enhance contrast and alter color.

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 i) Neutral Density Filters

When it is intended to uphold a specific lens opening for sharpness or depth-of-field

purposes, or merely to get appropriate exposure when exposed to high light intensity, neutral
density (ND) filters are used. This will absorb light consistently all over the visible
spectrum, efficiently fluctuating exposure without needing a change in lens opening and
without presenting a color shift.

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 j) Polarizing Filter:

Polarizers allow color and contrast enhancement, as well as reflection control using optical
principles different from any other filter types. Most light that we see is reflected light that
will take up its color and amount from the matters we are looking at. White light, as from the
sun, reflecting off a blue object, appears blue because all other colors are absorbed by that
object. A small part of the reflected light reflect back the object without being absorbed and
highlighted, holding the original (generally white) color of its source.

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 k) Filter Factor

This is the relative increase in exposure required when an optical filter is used. The filter factors
will not always be a persistent number. It depends on the colour of the filter as well as the hue &
saturation, the colour sensitivity of the film, the colour of the light and the colour of the subject.
Generally deeper the colour of the filter, higher the filter factor since it restricts more amount of
light. Manufacturers’ advice should be followed to get desired exposure. Exposure value
compensation is usually given in half or whole number such as ½ x, 2x, 3x etc.

7. Film Sensitivity

Orthochromatic films are sensitive to U.V., Blue-Green and slightly towards green of the
spectrum. Fast orthochromatic films are sensitive to Yellow-Green and slightly towards yellow
as well, but to a great extent to violet and blue. Panchromatic films are sensitive to all colours.

8. Colors of Light

Daylight is more blue and has higher colour temperature than the tungsten lamp (blue filter can
reduce the tungsten lamp effect). It should be noted that colour temperature of daylight depends
on the time of the day, weather and season. All films are over sensitive to blue, so subject like
landscape, blue sky is much too light(white) in the final print. The tone and the details between
sky and clouds are almost lost. This difference can be reduced by using a yellow filter. Orange
green filter often is used in daylight for proper tonal compensation.

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 a) Artificial Light

The most common lighting tools used today are tungsten light, fluorescent light, HMI light and
electronic flash. Each technology has distinct advantages and disadvantages. While I will discuss
each in detail, all have one key drawback in common, they are essentially fixed in terms of color
temperature. Because the color temperature is fixed, these light sources are not able to emulate
the ever-changing nuances of natural light. Digital cameras typically have presets for daylight,
flash, tungsten and fluorescent light sources in an effort to arrive at pleasing results under these
traditional illuminants.

b) Electronic Flash :

Originally, all flashes were manual in operation. That is, depending on the power of the
flash, the distance from the subject, and the film speed, we had to find the proper f-stop to
use. If we moved a few feet, we had to recalculate a new f-stop. In the 1960's, Honeywell
pioneered the automatic flash. This was quite an improvement, for now as you moved
around; the flash automatically provided the proper amount of light. This was accomplished
by adding a sensor to the flash unit. As light travels to the subject and bounces back toward
the flash, the sensor measures the light and quenches the flash when the subject has received
enough exposure. Automatic flashes are highly recommended. Most modern flashes have
three or four different automatic ranges, allowing different f-stops and working distances.
They can also be placed into manual mode for certain effects.

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 9. Summary

1. Camera lens is a transparent medium (usually glass) bounded by one or more curved
surfaces (spherical, cylindrical or parabolic) all of whose centers are on a common axis.
2. The distance between optical centre and focus is called Focal Length. Focal length,
usually represented in millimeters (mm), is the basic description of a photographic lens.
3. If the focal length of two lenses is the same, the lens with the larger diameter will be
brighter.
4. When it is desirable to maintain a particular lens opening for sharpness or depth-of-field
purposes, or simply to obtain proper exposure when confronted with too much light
intensity, neutral density (ND) filters are used.
5. All films are over sensitive to blue, so subject like landscape, blue sky is too light(white)
in the final print.

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 SUBJECT FORENSIC SCIENCE

Paper No. and Title PAPER No. 7: Criminalistics & Forensic Physics

Module No. and Title MODULE No. 28: Digital Photography

Module Tag FSC_P7_M28

FORENSIC SCIENCE PAPER No.7: Criminalistics & Forensic Physics

MODULE No.28: Digital Photography
 TABLE OF CONTENTS
1. Learning Outcomes
2. Introduction- Digital Photography
3. Advantages of Digital Photography over Conventional Photography
4. Digital Camera Sensors
5. Characteristics and Types of Digital Images
6. Resolution
7. Scaling/ Re-sampling
8. Bit Depth
9. Floating Point
10. Image Compression
11. File Format and Application
12. Levels and Curves
13. Image Noise
14. Lens
15. Important Factors in Digital Camera
16. Summary

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MODULE No.28: Digital Photography
 1. Learning Outcomes
After studying this module, you shall be able to know –
 What is Digital Photography
 What are the characteristics in Digital Photography
 Learn about Image compression, file format and its application

2. Introduction- Digital Photography

Digital Photography is in no way different or separate from conventional film or as we sometime say
analog photography except for the following things:-

 The image capturing medium.

 The image capturing principle or technique.
 The image storage device.
A digital camera also consists of a light constricted camera body as a film camera with a lens, an
aperture mechanism and a shutter control to control exposure. There are various models of Compact
Digital Cameras as well as Digital SLR Cameras with varying features. But whatever be the model
of the digital camera or the manufacturer, it works on the basis of same principle of an analog or a
film camera.
So, someone familiar in using a film camera can very well depict good pictures with a digital
camera. Therefore, as we have explained the basic principles of photography in earlier lessons, we
need not repeat them as they are true for digital photography also. The deviations will be clarified as
we go into the details of the topic afterwards in this lesson.

3. Advantage of Digital Photography over Conventional Photography

In modern world of imaging, digital photography certainly have some advantages over conventional
photography. The major among them are as follows:-

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 Film Photography Digital Photography

Films have limited exposure capacity like 24 or Digital Memory Cards can store much more
36 frames in a roll of film number of images. This gives us an opportunity
to shoot more pictures and since the card can be
reused, the cost of divulging is reduced to
minimal.
Images exposed through films could not be seen Digital Images can be seen instantly on the
unless the film is developed or printed. camera LCD display. Since we have an
immediate feedback of the image, we can correct
the focusing, exposure or composition if
required.
Once a particular film is loaded, the film speed Film speed can be changed easily in a digital
cannot be changed and exposure should be made camera just by pressing buttons or rotating a dial
accordingly. as desired.
Films are manufactured for a particular colour Colour temperature can be adjusted on a digital
temperature (daylight type or tungsten light camera according to external light condition or
type). requirement.
Video is not possible in a film camera. Video can be shot with a digital camera.
Preserving a film properly is not easy and editing Cataloging and editing digital is much easier on
an analog image in a darkroom needs great digital media.
amount of expertise.

4. Digital Camera Sensors

Digital Cameras are the most popular devices used to expose and capture a digital image. Although
we can capture digital images by scanning also but understanding the functioning of the digital
sensor which is a CCD or CMOS is the first step towards learning digital photography.
Fundamentally, a charge coupled device (CCD) is an integrated circuit etched onto a silicon surface,
forming a grid of several million tiny dots (photo sites) or light sensitive elements called pixels.
Photons incident on this surface generate charge that can be read electronically and turned into a
digital copy of the light patterns falling on the device. CCDs come in a wide variety of sizes and
types and are used in many applications from cell phone cameras to high-end scientific applications.

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 Each pixel in a CCD can remember how much light it received in a given period of time. When a
cameras shutter is pressed to expose a photograph, each of these picture elements are uncovered to
collect and store photons. As the exposure completes, the camera closes at each photo site and assess
the contents. The comparative amount of photons in each cavity is organized into different intensity
stages. There are three significant qualities to each sensor: resolution, size and quality.

CCD of different sizes Light Cavities

The function of a Charged Coupled Device can be seen as a selection of pixels collecting photons.

5. Characteristics and Type of Digital Image

A digital image is an exemplification of a 2D image using binary numbers i.e., 0 and 1. Dependent
on image resolution, it is fixed or not, it may perhaps be of vector or raster type. The word "digital
image" generally denotes to raster images also called as bitmap images.

 In digital imaging, a pixel, or picture component is a solitary point in a raster image, or

the minimum addressable screen element. It is the least unit of picture that can be
demonstrated or controlled.
 Each pixel has its own address like x/y axis of a graph.
 More pixels characteristically offer more exact representation of the original.
 The strength of each pixel is inconstant.
 In Color Image Systems, a color is characteristically signified by 3-4 component
intensities such as RBG, or CMYK.

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 6. Resolution
Resolution is a dimension of sample concentration, resolution of bitmap images gives a connection
between pixel dimensions and physical magnitudes. The most commonly used measurement is ppi,
pixels per inch. The difference between ppi and dpi, is the variance between pixels and dots - pixels
can denote manifold values, at the same time as a dot is a monochrome spot of ink or toner of a
single pigment as produced by a printer. Printers use a method called half toning to make a uniform
configuration that imitates a variety of intensity stages.
Resolution is simply the number of pixels. As more pixels we have, then the fine grained details we
can theoretically record. Any resolution above 2 or 3 megapixels (i.e. billions of pixels) will be
enough for displaying on a screen, but higher resolutions come into play for two important
applications: printing and cropping.

A rasterized form of the

letter 'a' magnified 16
times, where each pixel
is represented as a
circle instead of a
square.

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 To have a good reproduction quality, it is usually estimated that between 240 and 300 pixels should
be used for every inch of paper (dots per inch, or dpi), which will give a natural limitation to the
biggest size one can print. For example, a 6MP image of sizes 2000x3000 pixels can be reproduced
at a maximum size of 12.5x8.3" at 240dpi (2000/240 = 8.3, 3000/240 = 12.5). It is possible to print
bigger by either lowering the dpi or artificially increasing the resolution, but the image quality will
be poor. Having an advanced resolution permits us to print bigger.

7. Scaling/Re-sampling
When we require generating an image with diverse dimensions that we possess then we can measure
the image. A dissimilar name for Scaling is Re-sampling, when algorithms attempt to restructure the
original uninterrupted image and produce a new sample grid. The method of reducing the raster
dimensions is called decimation (Scaling Image down) this can be completed by averaging the
values of source pixels contributing to each output pixel. When we intensify the image extent we
essentially want to produce sample points among the original sample points in the original raster,
this is done by interpolation (Scaling Image Up) the values in the sample grid, effectively guessing
the values of the unknown pixels.
By the digital zoom of a camera, the camera is using interpolating to guess the values that do not
exist in the image. Capturing an image at the extreme analog zoom level and undertaking the post
dispensation of cropping and rescaling on the computer will give equal or better results.

8. Bit Depth
The values of the pixels must be stored in the computer’s memory. It means that the data eventually
need to end up in a binary representation; the spatial continuity of the image is approximated by the
spacing of the samples in the sample grid. The values we can represent for each pixel is determined
by the sample format chosen. Bit Depth is determined by the integer of bits used to describe each
pixel. So bit depth enumerates the number of unique colors available in an image's color palette in
terms of the number of 0's and 1's, or "bits," which are used to postulate each color. This does not
mean that the image essentially uses all of these colors, but that it can as an alternative specify colors
with that level of accuracy. For a gray scale image, the bit depth measures the number of available
unique shades. Images with greater bit depths can encrypt extra shades or colors since there are more
permutations of 0's and 1's available.
Bit Depth is proportional to the number of tones (grayscale or color) that can be represented. Digital
images may be created in black and white (bi-tonal), grayscale, or color. A bi-tonal image is
represented by pixels consisting of 1 bit each, which can represent two tones (typically black and
white), using the values 0 for black and 1 for white or vice versa. A grayscale image is composed of
pixels signified by manifold bits of information, typically extending from 2 to 8 bits or more.

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 9. Floating Point

Certain image formats used in research and by the movie industry store floating point values. Both
"normal" 32bit floating point values and a special format called half which uses 16bits/sample.
Floating point is advantageous as a working format because quantization and computational
inaccuracies are retained to a minimum until the final render. Floating point demonstrations often
include HDR or High Dynamic Range. High Dynamic Range images are images that comprise
sampling values that are whiter than white (advanced values than 255 for a normal 8bit image). HDR
allows representing the light in a scene with a greater degree of precision than LDR, Low Dynamic
Range images.

10. Image Compression

Bitmap images yield up a lot of memory. Image compression moderates the amount of memory
needed to store an image. For instance a 2.1 megapixel, 8bit RGB image (1600x1200) occupies
1600x1200x3 bytes = 5760000 bytes = 5.5 megabytes, this is the uncompressed size of the image.

Compression ratio is the ratio among the compressed image and the uncompressed image, if the
example image quoted above was stored as a 512kb jpeg file the compression ratio would be 0.5mb:
5.5mb = 1:11.

1. Lossless Image Compression

When an image is losslessly compressed, recurrence and probability is used to characterize all the
information by means of less memory. The original image can be restored. One of the unpretentious
lossless image compression methods is run-length encoding. Run-length encoding encodes
successive analogous values as one perfunctory in a data stream.

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 In the above figure “Run-length encoding” a black and white image of a house has been compressed
with run length encoding, the bitmap is considered as one long string of black/or white pixels, the
encoding is how many bytes of the same color occur after each other. It will further reduce the
amount of bytes taken up by these 72 numerical values by having a maximum span length of 15, and
encoding longer spans by using multiple spans separated by zero length spans of the other color.

2. Lossy Image Compression

Lossy image compression takes benefit of the human eyes capability to hide deficiency and the fact
that certain types of information are more significant than others. Modifications in luminance are for
example seen as more noteworthy by a human witness than change in hue. JPEG is a file format
applying compression based on the Discrete Cosine Transform (DCT), collectively with lossless
algorithms this delivers worthy compression ratios. The way JPEG works is superlatively matched
for images with constant tonal ranges like photographs, logos, scanned text and other images with
lots of sharp contours / lines will get more compression artifacts than photographs.

Lossy compression algorithms should not be used as a working format, only final copies should be
saved as jpeg since loss accumulates over generations.

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 11. File Format & Application
Several applications have their specific internal file format, whereas other formats are more
appropriate for transaction of data. Table below lists some common image formats.

Vector File Formats

Extension Name Notes
.ai Adobe Illustrator Document Native format of Adobe Illustrator (based
on .eps)
.eps Encapsulated Postscript Industry standard for containing vector
graphics in print
.ps PostScript Vector based printing language, used by
many Laser printers, used as electronic
paper for scientific purposes.
.pdf Portable Document Format Modernized version of ps, adopted by the
general public as 'electronic print version'
.svg Scalable Vector Graphics XML based W3C standard, including
animation, gaining adoption.
.swf Shockwave Flash Binary vector format, with animation and
sound, supported by most major web
browsers.

Raster File Formats

Extension Name Notes
.jpg or jpeg Joint Photographic Experts Lossy compression format well suited for
Group photographic images
.png Portable Network Graphics Lossless compression image, supporting
16bit sample depth, and Alpha channel
.gif Graphics Interchange Format 8bit indexed bitmap format, is superseded
by PNG on all accounts but animation
.exr OpenEXR HDR, High Dynamic Range format, used by
movie industry.
.raw, Raw image file Direct memory dump from a digital camera,
contains the direct imprint from the imaging
sensor without processing with white point
and gamma corrections. Different cameras
use different extensions, many of
thederivatives of TIFF, examples are .nef,
.raf and .crw
.dgn Digital Negative A subset/clarification of TIFF, created by
Adobe to provide a standard for storing

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 RAW files, as well as exchanging RAW
image data between applications.
.tiff, .tif Tagged Image File Format
.psd Photoshop Document Native format of Adobe Photoshop, allows
layers and other structural elements
.xcf Gimp Project File GIMP's native image format.

12. Levels and Curves

Curves: It is simple information of layers and masks, this climbs to something like 80%. Even
though curves are comparatively direct, there is a basic form of the tool which, while losing some
power, is often sufficient.
Levels: Levels and curves transform exposure and, by extension, contrast. In order to be used
efficiently, it is essential to have a respectable understanding of the histogram. As you may recall,
we said in the histogram lesson that a "perfect" histogram is one which has a bell shape, tapering off
in both directions and ending exactly at the edges, which correspond to pure white and pure black.
You don't want it to end after the right edge, for instance, because it would mean that you are losing
information and getting pure white, it means that there are no really bright values in the image,
which will make it appear dull and washed-out, lacking contrast.
Levels essentially resize the box, so that the histogram fits into it perfectly. There are three controls:
black, grey and white points. Let's forget about grey for now and focus on black and white. If you
slide them around, they will describe the new edges of the box in which the histogram subsists.

13. Image Noise

"Image noise" is the digital corresponding of film grain for analogous cameras. Alternatively, one
can contemplate of it as analogous to the delicate background hiss perceived from the audio system
at full volume. For digital images, this noise seems as random flecks on an otherwise smooth surface
and can significantly destroy image quality. Even though noise regularly reduces from an image, it is
occasionally required since it can increase an old-fashioned grainy look which is suggestive of early
film. Some noise can also increase the apparent sharpness of an image. Noise rises with the
sensitivity setting in the camera, length of the exposure, temperature, and even differs amongst
different camera models.

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 14. Lens
The lens is the second constituent of any camera. It is an optical device which receives scattered
light rays and focuses them precisely on the sensor. The quality of the glass and the accuracy of the
lens will be particularly imperative in determining the quality of the final image.
Focal length denotes roughly to the "zoom level", or angle of view, of the lens. It will have its own
lesson in a few days, as it can be an unexpectedly complicated subject. A focal length is generally
expressed in millimeters, and you should be cognizant that the resulting angle of view actually
depends on the dimensions of the sensor of the camera on which the lens is used (this is called the
crop factor). For this reason, we often give "35mm equivalent" focal lengths, which is the focal
length that would offer the similar view on a 35mm camera (the historic film SLR format) allows us
to make expressive comparisons. If there is a single length (e.g. 24mm), then the lens doesn't zoom,
and it is often called a prime lens. If there are two numbers (e.g. 18-55mm), then you can use the
lens at any focal in that range. Compact cameras often don't provide focal lengths but basically the
range, for instance 8x, this means that the long end is 8 times longer than the wide one, so the lens
could be a 18-144mm, or a 35-280mm, etc.
The aperture is a very substantial concept which we will talk about in much detail later on. The
aperture is an iris in the centre of the lens, which can close to gradually small sizes, restraining the
amount of light which gets on the sensor. It is stated to as f-number, for instance f/2.8. To make
things inferior, it is quite counter-intuitive, as the smaller the number, the bigger the aperture! For
now, we don't have to worry about this too much. The significant number on a lens is the maximal
aperture, the lower the better. Professional zoom lenses often have f/2.8 maximal apertures, and
economy consumer lenses have ranges such as f/3.5-5.6, meaning that at the wide end, the maximum
aperture is f/3.5 and at the long end, it is f/5.6. Aperture can be closed to tiny levels, usually at least
f/22.

15. Important factors in Digital Cameras

SHUTTER
The most essential is probably the shutter. Think of it as a curtain in front of the sensor. When we
press the trigger, the curtain opens, exposes the sensor to light from the lens, then closes again after a
very specific amount of time, often a tiny fraction of a second. Most shutters operate between 30
seconds and 1/4000s of a second. That duration (the shutter speed) is one of the three very
significant exposure factors, along with aperture and ISO.

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 The best place to see the shutter speed setting on the camera is in the viewfinder. Half-press the
shutter button activated the camera & the viewfinder & we can see the shutter speed which is the
first number at the bottom.

FOCUSSING
A focus detector, used to drive the autofocus motor in the lens. There are two contending
technologies, contrast detection and phase detection, with one at the moment an edge for the latter,
which explains why DSLRs tend to focus faster than compact cameras. These systems have a habit
to vary greatly between basic and advanced bodies, but it should be noted that they all need rational
amounts of light to work appropriately.

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 MEMORY CARDS
An approach to store the image just generated. Back in the days of film, this was just a lever to
advance the roll to the next unexposed frame. Now, it is a pipeline which ends up in the memory
card that the camera is using. If we are shooting JPEG instead of RAW, there is an additional stage
where the internal computer executes all sort of black magic on the image to output a ready-to-view
jpg file.

VIEWFINDER

``Way to frame or compose the image. It can be an assembly of things, optical or electronic
viewfinder, LCD screen or even ground glass. Here too, DSLRs have an edge, as an optical
viewfinder allows "through-the-lens" viewing and immediate feedback, while electronic viewfinders
( a LCD screen inside a viewfinder) and LCDs often have limited resolution and slight updating
delays.

Optical Viewfinder (OVF) Viewfinder Switch Lever Electronic

Viewfinder (EVF)

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 EXPOSURE
In order to keep things short, we can divide this vast subject into small parts. Here we will see what
exactly exposure is, and how we can use three camera controls to modify it. Afterwards we will talk
about a very important tool for revising exposure: the histogram. Consequently we will talk about
each of the three controls (shutter speed, aperture and ISO) in more detail. Exposure basically, is the
amount of light to which the sensor is exposed.

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 ISO
The ISO speed, also occasionally known as sensitivity is alternative major factor to control exposure
in any digital camera. ISO is one of the essential differences between film and digital. It is a physical
property of the film we are exhausting, and the only way to modify it is to change to a new roll - not
the most appropriate. With digital, we can easily change ISO between shots, merely by turning a
wheel, which permits flawless adaptation to the current light conditions. For those who shot film a
long time ago, you may have used diverse words for sensibility: ASA or DIN. The first is exactly the
alike than our current ISO, it simply changed name when it became homogeneous. The latter uses
another logarithmic scale and is absolutely outdated. Transformation between the two is quite
straightforward, though.

16. Summary
1. A digital camera like a film camera also contains light body with a lens, an aperture
mechanism and a shutter control to control exposure.
2. A digital image is a depiction of a two-dimensional (2D) image using ones and zeros
(binary).
3. Bit Depth is determined by the number of bits used to explain each pixel. So bit depth
computes how many unique colors are accessible in an image's color palette in terms of the
number of 0's and 1's, or "bits," which are used to depict each color.
4. ISO is one of the important dissimilarities between film and digital cameras.

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 SUBJECT FORENSIC SCIENCE

Paper No. and Title PAPER No. 7: Criminalistics & Forensic Physics

Module No. and Title MODULE No. 29: Ultraviolet & Infrared Photography

Module Tag FSC_P7_M29

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MODULE No.29: Ultraviolet & Infrared Photography
 TABLE OF CONTENTS
1. Learning Outcomes
2. Introduction
3. Radiation Source of Ultraviolet Rays
4. UV photography with Digital Cameras
5. Chemical Photography
6. Requirement of UV Light Photography
7. Focusing and Exposure
8. Uses in Forensic/ Law Enforcement
9. Photographic necessities for reflected UV radiations
10. Infrared Photography
11. Summary

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MODULE No.29: Ultraviolet & Infrared Photography
 1. Learning Outcomes
After studying this module, you shall be able to know –
 About Ultraviolet and Infrared Photography
 Various radiation sources of ultraviolet rays
 UV photography with Digital and Film Cameras
 Uses of Photography in Forensic/ Law enforcements

2. Introduction: Ultra violet and Infrared Photography

Wavelength of Visible Light
Electromagnetic radiations are light, however we are able to see a small part of radiation—the
portion we call visible light. Other part of the spectrum has wavelengths very high or very less
and beyond the limit of our visual perception. The Visible White light splits into seven colors of
rainbow, having different wavelength when it is passed through prism. Violet Colour shows the
shortest wavelength, at 380 nanometers, and Red has the longest wavelength, at 700 nanometers.

Electromagnetic radiation vary is their energy range. Ultraviolet radiation is very active
than visible radiation and therefore has a shorter wavelength. To be more precise: Ultraviolet
rays has wavelength between 100 nanometers and 400 nanometers approximately
whereas visible radiation includes wavelengths between 400 and 780 nanometers.

Ultraviolet spectrum is classified into the following bands:-

i. Long wave ultraviolet
ii. Middle ultraviolet
iii. Short wave ultraviolet
iv. Vacuum ultraviolet

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 i. Long wave Ultraviolet:
It extends from 3200 Ao to 4000 Ao. This is the range transmitted by regular optical glass of
which most photographic lenses are made. This range is most practical value in ultraviolet
photography.
ii. Middle Ultraviolet:
Between 2800 – 3200 Ao lies in this region. Middle ultraviolet radiations are not transmitted by
even photographic lenses. A lens made of quartz however will transmit these rays and could
therefore produce an image using them. Quartz lenses however can also transmit longer
ultraviolet.
iii. Short Wave Ultraviolet:
This region lies between 2000 – 2800 Ao and is also called ultraviolet. One should never look
straight at a source of shortwave ultraviolet radiation. A quartz lens will transmit most
wavelengths of short ultraviolet.
iv. Vacuum Ultraviolet:
This region is shorter than 2000 Ao and up to 100 Ao which is upper limit of X –rays. These
radiations pass through vacuum and have no practical value in photography.

UV Rays can be classified into three bands according to their frequencies as given above in the
visual.

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 3. Radiation source of Ultraviolet Rays
1. Sunlight:
Although it would be possible to use sunlight as a source of UV to produce fluorescence,
but it is not a practical procedure as it is not followed for forensic photography.

2. Mercury Vapour Lamps:

Mercury vapor lamps, both high pressure and low pressure have applications in reflected
and fluorescence photography. All mercury vapor lamps however emit long wave
ultraviolet and if the tube is made of quartz, then shorter waves of ultraviolet may also be
emitted. A high pressure mercury arc lamp emits a high output of long wave ultraviolet
with a corresponding result of intense fluorescence particularly in subjects of small area.

3. Electronic Flash:
Electronic flash lamps are suitable for ultraviolet photography since they emit long wave
ultraviolet. One of the difficulties encountered in using electronic flash is that resulting
fluorescence is not perceptible during the short flash interval.
The electromagnetic spectrum is invaluable for forensic photography. This comprises
wavelengths in the visible spectrum and those that are invisible to the human eye. While
we can only see the narrow range of light in the visible spectrum, we can use special
cameras to take images of objects, documents as well as human body using ultraviolet
and infrared wavelengths, which allows us to gain even deeper insights.
By responding to ultraviolet and infrared light, the camera reveals information that is
otherwise concealed from the human eye.

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MODULE No.29: Ultraviolet & Infrared Photography
 Multispectral imaging can also be used to read & record faded or burnt manuscripts - even from
carbonized and damaged fragments. We can recover washing off the original ink & overwritten
with new text. These washed out inks can still be read using the appropriate wavelength of
light. The UV range (400-360nm) produces ultraviolet fluorescence images (UVF) and
ultraviolet reflected images (UVR). The infrared electromagnetic radiation most close to the
visible range (1100-780nm) can be detected by a special camera/attachment, which is used to
collect infrared CCD images (IRCCD) and infrared false color images (IRFC). More
sophisticated cameras can detect infrared light even further down the range (1100-1700nm),
producing infrared reflectography images (IRR).

There are two kinds of photography that should not be mixed up: Fluorescence and UV-reflected
photography.

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 LUMINESCENCE FLUORESCENCE PHOSPHORESCENCE

When certain materials If the luminescence ceases in a There are some substances
(solids, liquids or gases) are very short time (10-8 seconds) which continue to emit
subjected to short wave after the exciting radiation is luminescence for some time,
electromagnetic radiation, removed, the phenomenon is even hours after removal of
they will emit another called fluorescence. the exciting stimulus (e.g. TV
radiation of longer wavelength screen, Oscilloscope, certain
very often in the visible chemicals and living
spectrum. organisms.)
This phenomenon of induced
light emission is called
luminescence and there are
two distinct types –
fluorescence and
phosphorescence

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 The first, fluorescence photography, involves illuminating the subject with UV (―black‖) light
and the subject returns this radiation with lower wavelength, inside the visible spectrum, being
photographed with conventional photography.

UV Fluorescence imaging:
UV illumination stimulates fluorescence at a longer wavelength than the UV excitation source.
The resulting fluorescence is typically in the visible band. A color camera with a UV-blocking
filter is used to record the fluorescence image.

Photoluminescence –
SWUV excited LWUV fluorescence probably not a common form of fluorescence photography
as it requires a very controlled SWUV excitation source, typically narrow band. A barrier filter
that transmits LWUV and blocks SWUV is necessary for the lens. Unfortunately, most
photographic lenses will fluoresce to some degree resulting in a foggy image. Lenses specially
designed for reflected ultraviolet photography should fare much better. It is not possible to use a
readily available SWUV lamp in this application as they also emit some LWUV light.

Visible excited visible fluorescence –

This is very similar to visible excited infrared, except of course the fluorescence occurs in the
visible region of the spectrum. The excitation is typically blue or green light and the fluorescence
red. However, fluorescence can be green, yellow or orange as exhibited by many "fluorescent"
dyes and inks. Capturing visible fluorescence excited by visible light can be very challenging
and often requires narrow band excitation sources and sharp cut-off filters. It is also important to
exclude infrared from the excitation source or the environment.

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 4. UV Photography with Digital Cameras
Digital sensors are sensitive to a wide and undesirable spectrum of radiations, from near UV to
the IR. Camera manufacturers try to avoid these undesirable side-effects that affect the quality
and sharpness of the photographs.

Usually all cameras have built-in filters of the so-called ―Hot Mirror‖ type that eliminate totally
the UV from the photographs. CCD and CMOS image sensors of digital cameras incorporate
strong UV and IR filters to achieve good color accuracy with standard visible-light subjects.
Normal Digital-SLR cameras are not very sensitive in the UV, but very much to IR ranges.

5. Chemical Photography and Films

All photographic films (color negative and slides, black-and-white, infrared) are sensitive to
ultraviolet radiation (because silver halide crystals are sensitive to it). There is no significant
advantage to using color film for reflected ultraviolet photos because only the blue layer of the
tri-color pack will be exposed by the ultraviolet (the integral yellow filter of the film effectively
preventing exposure of the red and green layers). The typical film photography method starts
with a panchromatic film like Kodak T-Max 400 which has good response to UV. The
photographer has to use a special UV-pass filter that blocks visible light from reaching the film,
but this black glass filter also prevents the photographer from composing the shot or focusing it
properly while it is installed.

Some materials will absorb ultraviolet, while others will reflect these radiations. Some have
partial reflection. These effects can be recorded photographically using ultraviolet radiation.
Black-and-white films are sensitive to most wavelengths of ultraviolet. By using a filter that
absorbs all visible light but passes ultraviolet, it is possible to make a photographic exposure
with just ultraviolet.

6. Requirements for UV light Photography

UV Source:
Any Flash with UV Filter or any other UV light source. Instead of a UV source, flash can be
used. A high output studio flash will emit a fair bit of UV.

UV Sensitive Camera:
Specialist cameras converted to be sensitive only to UV, however the cheapest commercial
option is to simply use black and white film. Black and White Film has sensitivity to UV
however the images may undergo reduced contrast.

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 UV Transmission Filter:

A Filter such as the Kodak Wratten 18A (which leaks a little IR) or Baader Venus 1.25″
Ultraviolet Transmission Filter.

Tripod:
Exposure times can be long therefore a tripod is necessary.

Light Meter:
Although fairly useless, this might help sometime.

The lens we use may be good or bad for UV — lenses often contain coatings to block UV — so
a little experimentation is required. Alternatively, a quartz lens can be used (Nikon used to make
a UV-Nikkor but very costly).

7. Focusing and Exposure

Focusing has to be done for visible light and then shooting for maximum depth of field to get the
correct focus. Accurate focus and exposure for ultraviolet photography requires test exposure.
The ISO of film will be much different for ultraviolet photography. A film with a speed of ISO
400 for visible light may have an effective speed of ISO 10 for ultraviolet photography.

8. Uses in Forensic/Law Enforcement

• Ultraviolet photography has to be used after visible light techniques and infrared light
techniques fail (questioned documents, security documents etc.)
• Fingerprints on multicolored surfaces (dusting with fluorescent powder or ninhydrin is
necessary).
• Body secretions such as urine, semen and perspiration often glow when illuminated by
ultraviolet light.
• Money and other valuables can be dusted or marked to identify thieves.

9. Photographic Necessities for Reflected UV Radiation

i. In a situation when we are taking photograph of an object by illuminating it with a
radiation source that emits ultraviolet. The subject has to be illuminated
proportionately from at least two sides.
ii. All visible light has to be excluded from the camera by placing over the lens a filter
that transmits only UV.
iii. The image has to be recorded in the camera on the film.

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MODULE No.29: Ultraviolet & Infrared Photography
 iv. We have to take necessary precaution like increasing the contrast in the following
situation

Blood In situation where its Colour blends with surroundings

Documents Erasures, forgeries & faded documents
Inks & printer ribbons-since pigments vary in the absorption and
reflection of ultraviolet
Invisible stains Various body secretions such as: urine, semen, pus, perspirations etc.
as they often emit a particular fluorescence.
Clothing White clothing particularly may fluoresce an intense white blue
because dyes are used in laundry detergent makes them look brighter
& white. The use of UV light under water has been suggested as an
aid in locating human bodies because of these common fluorescence
in clothing.
Fingerprints On multicoated backgrounds, shiny or concave objects, organic
matter (all using fingerprint powder).

Result of Reflected UV Light Photography on human body

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MODULE No.29: Ultraviolet & Infrared Photography
 This baby was photographed in normal light and UV light. She had very minimal exposure to the
sun, and always with sunblock, thus there is no evidence of sun-induced hyper pigmentation. In
the UV reflected photograph on the right, the mark on her cheek is a scratch.
The burn on the subject’s thigh was caused by burning kerosene. The oil-producing cells in the
skin are damaged, so the skin appears lighter in the UV band, since skin oils absorb UV.
Severely sun-damaged skin will appear lighter as well.

100 Euro bill UV security features under UV light

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 10. Infrared Photography
Sir Frederick William Herschel, a German-born British astronomer, discovered infrared light on
11th February 1800. While using a variety of colored filters to view sunlight, he observed that
some colors passed more heat than others. Herschel hypothesized that the colors themselves may
have actually produced different temperatures and set out to test his theory.

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 Herschel conducted an experiment measuring the difference in temperature between the colors in
the visible spectrum. He placed thermometers within each color of the visible spectrum. The
results showed an increase in temperature from blue to red. When he noticed an even warmer
temperature measurement just beyond the red end of the visible spectrum, Herschel had
discovered infrared light!

A typical television remote control uses

infrared energy at a wavelength around
940 nanometers. While we cannot "see"
the light emitting from a remote, some
digital and cell phone cameras are
sensitive to that wavelength of radiation.

Infrared lamps heat lamps often emit

both visible and infrared energy at
wavelengths between 500nm to 3000nm
in length. Heat lamps can also keep small
animals and reptiles warm or even to
keep eggs warm so they can hatch.

The infrared range begins at wavelengths of 700 nm (at the red end of the visible spectrum) and
extends toward longer wavelengths. Both sunlight and incandescent light sources contain large
amounts of infrared. The sensors used in digital cameras are very sensitive to near-infrared (700-
1200 nm). Virtually all digital cameras use infrared-cut filters sandwiched on top of the sensor,
in order to reduce or eliminate IR light. Many of these filters let usable amounts of IR pass (up to
about 900 nm), and these cameras can be used for IR photography. The built-in IR-cut filters are
of varying construction and effectiveness, which makes different camera brands and models
more or less suitable for IR photography. Among Nikon DSLRs, the D70 and D70s are reported
to be particularly suitable for IR photography.

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 Radiation source for Infrared photography
Sun Light: Sun Light contains a high percentage of I.R. radiations and therefore a very useful
natural source of infrared radiations.

Hot Bodies: All sources which emit or generate heat also emit I.R. radiations in various
proportions. Even the human body emits I.R. radiations. This fact has been used in detecting
military installations, human beings and animal life in complete darkness with the help of I.R.
photographs and I.R. detecting devices.

Tungsten lamps: In laboratory, tungsten filament lamp is the most commonly used source
of I.R radiations. The various types of tungsten filament lamps are 500 or 1000 watts like the
photoflood lamps and halogen projection lamps. I.R lamps coated with graphite are available
which are specially made for I.R. photography since the visible light may be opaque to graphite
and only I.R radiations are emitted.

Photoflash Lamps: It is practical to coat a dark red, infrared transmitting envelop over
photoflash.

Electronic flash units: Electronic flash units have many advantages in the photography of living
subjects. Their benefits of coolness and short exposure time are extendable to infrared
photography. Another advantage of these units is that they are more readily obtainable with
compact reflectors than the tungsten photoflood equipment.

Infrared photography has found several applications in criminological investigations of faded,

erased, burnt, worn, dirty or altered documents, the differentiation between pigments, dyes and
inks which may appear indistinguishable to the eye. Infrared photography also helps in
examination and identification of cloth, fibers and hair, detection of secret writing and variety of
other applications. Infrared can decipher printings or writings underlying the obliterating ink
which although black to naked eye in visible light happens to be transparent to infrared.

Mechanical or chemical erasure can sometimes be determined even if over written, provided of
course the overwriting is an ink transparent to infrared.

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 In visible light the check
looks to be written for
$400 dollars.

In 830nm (Deep BW)

Infrared light you can
clearly see the original
amount was $100

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 The photograph at left depicts black cotton fabric with a bloodstain. The photograph at right was
taken using infrared reflected with the Fuji S3 UV/IR digital camera with Peca 900 (18A) filter.
The black cloth is rendered white and the bloodstain readily visible. ISO 400, F16, 1/750,
Tungsten cross lighting

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 The photograph at left depicts synthetic upholstery with a bloodstain. The photograph at right
was taken using infrared reflected with the Fuji S3 UV/IR digital camera with Peca 906 (87A)
filter. The fabric is rendered white with pattern neutralized and the bloodstain readily visible.
ISO 400, F16, 1/20, Tungsten cross lighting.

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 11. Summary
1. Ultraviolet radiation is more energetic than visible radiation and therefore has a
shorter wavelength.
2. A lens made of quartz however will transmit these rays and could therefore produce
an image using them. Quartz lenses however can also transmit longer ultraviolet.
3. There are some substances which continue to emit luminescence for some time, even
hours after removal of the exciting stimulus (e.g. TV screen, Oscilloscope, certain
chemicals and living organisms.)
4. All visible light has to be excluded from the camera by placing over the lens a filter
that transmits only UV.
5. The infrared range begins at wavelengths of 700 nm (at the red end of the visible
spectrum) and extends toward longer wavelengths.
6. Infrared photography has found several applications in criminological investigations
of faded, erased, burnt, worn, dirty or altered documents, the differentiation between
pigments, dyes and inks which may appear indistinguishable to the eye.

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MODULE No.29: Ultraviolet & Infrared Photography
 SUBJECT FORENSIC SCIENCE

Paper No. and Title PAPER No. 7: Criminalistics & Forensic Physics

Module No. and Title MODULE No. 30: Special Photographic Techniques used in
Forensic Application
Module Tag FSC_P7_M30

FORENSIC SCIENCE PAPER No. 7: Criminalistics & Forensic Physics

MODULE No. 30: Special Photographic Techniques used
in Forensic Application
 TABLE OF CONTENTS

1. Learning Outcomes
2. Introduction
3. Photomicrography
4. Close-up and Macro Photography
5. Sharp Images
6. Controlling Light’s Direction
7. Small Evidence
8. Various Lighting Arrangement
9. Summary

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MODULE No. 30: Special Photographic Techniques used
in Forensic Application
 1. Learning Outcomes
After studying this module, you will be able to know –
 What is Photomicrography , Close up and Macrophotography
 How to Control Light’s direction
 Various light arrangements available.

2. Introduction
Making photographic records or imaging for microanalysis of various kinds of evidential objects
through various techniques is a challenge in forensic science. Be it a small part of a human hair/
fiber or a cleverly forged document involves the use of photomicrography, macro-photography
and other techniques like using oblique light , transmitted light etc. Before going in depth of the
techniques, let us learn the definitions of Microphotography and Photomicrography
The Royal Microscopical Society states:
1) Microphotography - "Photography, particularly of papers, arranged to create small images
which will not be studied without enlargement. Not to be tangled with photomicrography." This
is generally not required in forensic imaging.
2) Photomicrography - "The recording by taking pictures of an image created by a microscope;
i.e. photography through a microscope. This should not to be confused with microphotography."
Forensic Documentation often needs to take pictures of objects like blood spatter on walls,
footwear impressions, or innumerable small objects on the ground. Sometimes it is the less
significant features of superior objects that assist as the evidence. The photographer must be
imaginative, impulsive and also prepared to properly capture the pictures of these kinds of
subjects with accuracy. Take pictures of all evidence at proper place or the situation as
discovered before the gathering and transference to the laboratory for documentation and
analysis . Photographing the location, orientation, situation, and relationship of an object within
the scene as a whole is just as critical as photographing close-ups of the evidence.

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 3. Photomicrography

Photomicrography is extensively used in forensic labs and other fields which require study of
minute particulars. In the 19th and 20th centuries, photomicrographs, also called micrographs,
were formed by linking or bring into line a film camera with a microscope, a complex procedure.
Digital technology had permitted the two devices to be by electronic means synched in order to
view live images in real time.

Photomicrography was pioneered in the 1800s and scientists rapidly appreciated that it will
enable the study of microscopic matter. When forensic science started using it in crime
investigation in 20th century, photomicrography turned out to be a vital tool for examining trace
evidence, tiny details that can connect a suspect to a crime scene.
Camera zoom lenses and microscopes based on the basic principle by using magnifying lenses,
and sometimes mirror, to expand a point while holding clear focus. Initial photomicrography
comprises complex settings of cameras and microscopes. Digital technology has eliminated and
eased the requirement for such painstaking device arrangement & alignments.
In Photomicrography, the variety of entire magnification is generally from 10x to 1000x. , total
magnification will depend on the magnification of the optical setup, on the size of the image
sensor and on the size of the paper print (or on the size of the image displayed on a computer
screen). The main aspect of photomicrography is the lighting, which comprises the kind of light
source, collector lenses, condenser, and correction filters.
There are various different settings used for the purpose of photomicrography. The important
center here is the arrangement of a digital camera and a compound microscope. Examples of
consumer grade digital cameras are the SONY Cyber-shot, Nikon Coolpix or Canon Power Shot
cameras and others. All given cameras have a serial link to a computer system and a non-
removable zoom-lens. There are essentially three different ways of using such a consumer grade
digital camera to take out pictures by a microscope.

The first one, a very basic and inexperienced way of taking pictures, is to use an eyepiece with a
rubber ring. It is recommended to grip the camera body with one hand and use manual focusing.
With some practice, it is likely to take quite reasonable images with this simple setup.

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in Forensic Application
 The second possibility is using an adapter that directly mounts the camera to a regular eyepiece.
This is chiefly suggested if the optical arrangement needs a compensating eyepiece to entirely
precise for lateral chromatic aberration.
The third setup is same like second one. Here the camera is fixed on a phototube. The use of a
phototube suggests the most even configuration and helps significantly to avoid vibration or
camera shake.

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 Viewing & Capturing image from the camera:
Instead of connecting the digital camera's video output to a TV monitor, we can also connect the
video signal to a video frame grabber card, which is part of a PC. With such a setup, a
microscope can be easily used as a video microscope and record or grab images from video
signal. We can also use a camera that connects a PC via FireWire (IEEE 1394) or USB port.

Using manual focus and aperture priority mode with the widest possible aperture or smallest f-
stop number, which depends on the zoom setting is beneficial along with manual exposure mode.
The brightness has to be adjusted in such a manner that the exposure time of the camera is
1/100 second or faster.

To confirm the correct color temperature, using gray filters and suitable blue filters is more
appropriate. The Nikon Eclipse microscopes support a nice feature that allows adjusting for the
correct color temperature more easily using a special photo-button on the left side of the frame.

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 Photomicrograph of Scissor-Cut Hair Photomicrograph of Pigment
Distribution in Human Hair

4. Close-up and Macro Photography

Macro-photography is the form of photography, known to be the photography of small objects.
The fine details noticed in a macro photograph can deliver extraordinary information. A close-
up of a blown fuse can give clues as to how the fuse blew. Alternatively, clean round ends on
the separated fusible link would specify a longer and less severe condition.

Close-up Photography can help provide

information about how a fuse blew, as well as
document the fact that it did blow.

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 Magnification is an important aspect of macro photography. Magnification explains the
association between the real size of the object and the size of its picture on the sensor of the
camera. Photographing a 3 cm (1.18 inch) long subject so that its image size is 1 cm (0.39 inch)
on the sensor means that the magnification is 1/3 (1:3) life-size. Dividing the size of the object’s
image on the sensor by the real size regulates the magnification. At 1:1 life-size, the size of the
object on the sensor is as higher as it is in actual life.

1:1 magnification 1:4 magnification 1:8 magnification

Macro photography is restricted to magnifications in the order of 1:10 to 1:1 life-size. More
enlargements are likely with a microscope.

Larger than Life-size

Most macro lenses are maximally able to capture a 1:1 life-size image of a subject on the
camera's sensor. It is a macro lens only if it can achieve this 1:1 magnification. A low-budget
method to decrease the minimum focusing distance is to extend the distance between the lens
and the sensor by inserting extension tubes or an adjustable bellows. Extension tubes and
bellows do not contain optical elements. The farther the lens is from the sensor, the closer the
minimum focusing distance, the greater the magnification. A small disadvantage is that the use
of extension tubes and bellows may not preserve autofocussing, auto exposure and auto aperture
operation. The maximally obtainable magnification can be calculated with the following simple
equation: D (length of the set of extension tubes or the bellows) + F (focal length of the macro
lens) ÷ F = magnification.

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 For Example: Adding a set of extension tubes with a total length 0f 60 mm to a 60 mm macro
lens will give maximally a magnification of (60+60) ÷ 60 = 2.
By adding a teleconverter, an even greater magnification can be achieved. Application of a 2x
teleconverter produces a maximum magnification of 4 and 2 stops loss in light intensity. Placing
an auxiliary close-up lens (or close-up "filter") in front of a macro lens is another option.
Inexpensive screw-in or slip-on attachments provide close-focusing at a very low cost. Most
close-up lenses are marked with a +d number in dioptre unit, the power of the lens. The dioptre
(or power) of a lens is defined as 1000 ÷ Fd, where Fd is the focal length of the lens measured in
mm. Thus, a lens with a focal length of 50mm has a dioptre of 1000 ÷ 50 = +20, and a +4
dioptre close-up lens has a focal length of 250mm = 1000 ÷ 4. The maximally obtainable
magnification can be calculated with the equation (2F + Fd) ÷ Fd.
For Example: coupling a +20 dioptre lens with a 60 mm macro lens produces maximally a
magnification of (2 × 60 + 50) ÷ 50 = 3.4.

5. Sharp Images
Working with large magnifications means that the subject is only a few centimeters in front of
the lens. As magnification increases, depth of field decreases rapidly. Due to loss of light and
depth of field considerations, a ring flash or twin lite flash can be used. It will allow us to shoot
at a smaller aperture for sufficient depth of field and a fast shutter speed (e.g. 1/200 sec). It is
critical to focus carefully in microphotography since the limited depth of field available isn’t
sufficient to mask minor focusing errors.

6. Controlling Light’s Direction

Controlling light for studio photography is placing the light in such a way so that the subject's
three-dimensionality can be emphasized: Lights should be always off to the side or slightly
above and never on axis.

i) Front- or axial lighting: Here the light originates at the camera. The best-known
example is on camera flash. Axial lighting, especially when it is the primary
photography lighting source, renders its subject flat and shadow less.

ii) Side lighting (45 degrees to axis): Moving the light source to a 45 degree angle to
the taking axis reveals shadows. This adds to the sense of depth in our subjects.

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 iii) Texture lighting (90 degrees to axis): Light that grazes a surface from a low angle,
it shows off the texture and structure of surfaces.

iv) Backlighting: Light that originates from behind the subject can be useful especially
with transparent or semitransparent subject. This is useful in document photography.

v) Specular lighting: Specular highlights are bright reflections off of shiny surfaces,
originating from point-source lighting. They show up in photographs as very bright
points. Specular highlights are a side-effect of the main lighting source. Here are
some examples:

vi) Front/axial lighting (left) shows no depth, whereas 45° degree side lighting (right)
begins to show some of the form of the orange.

vii) On the left, front-lighting casts a distracting shadow and creates reflections. On the
right, the same light was bounced off of a white card placed behind the glass,
achieving two effects i. pleasing back light, which causes the liquid to "glow" and ii.
a soft light, eliminating hard-edged shadows (note, the highlights on the rim).

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 7. Small Evidence

This image was exposed with a ring-flash on the

camera to reduce harsh shadows that could be
caused by the high ratio of subject relief to subject
size.

The distorted filament inside this car headlight

indicates that the low beam of the headlight was in
operation when the vehicle encountered an
obstruction. It was not possible to use a scale on the
image so the magnification had to be calculated.

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 Include scales and references in images to enable post-process sizing and placement.

1. Built- in camera flash

The built-in flash on a camera may be suitable for general photography but it is not appropriate
for macro or close up photography. The lighting from these flashes is generally too direct and
harsh. As such, the camera’s built in flash should be used as a last resort for macro or close up
photography.

2. Hot shoe flash

The hot shoe electronic flashes are external flash units that fit onto the top of DSLR camera.
These flashes can generally be used for all types of photography. It is possible to use a hot shoe
flash unit for macro photography however it may sometimes be difficult to achieve the right
lighting.

3. Macro ring light / flash

Macro ring light / flash units were originally made for dental photography however they are now
commonly used in macro photography. A macro ring flash is a circular flash unit that is mounted
to the end of the lens. They lit up the subject evenly and provide a shadow less image. As such,
these are suitable to be used in poor light condition.

4. Double / Dual / Twin macro flashes

The double / dual / twin macro flash units are the ultimate flash for all macro photographers.
Instead of a single circular flash unit, two flash units (very similar to mini hot shoe flashes) are
mounted around the lens and they can be moved around in a circular motion. Double macro flash
units can be controlled individually.

8. Various Lighting Arrangement

1. Direct Lighting
It uses normal copy lighting with one or more light sources at 45-degree angles.

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 2. Direct Reflective Lighting
In this, light is reflected from the object into the lens. Put the object at a 10-degree angle from
the lens to film plane and put the light source at 10-degree angle from the subject. The light
source reflects at a 20-degree angle into the lens. The light source may need to be diffused to
prevent hot spots. This method creates very high contrast.

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 Shadows caused by poor
flash placement in direct
lighting.

3. Oblique Lighting
It uses a light source at a low angle, usually to mark detail through shadows in the subject
surface. It is usually used when photographing impressions, tool marks and various kinds
of fingerprints.

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 Footwear impressions photographed
using oblique light

4. Bounce Lighting
Light is bounced off a white or reflective
surface. The bounce surface may be
positioned at different locations (above or to
one side of the subject) to create the desired
effect. This usually produces even non-glare
lighting with low contrast.

5. Diffused Lighting

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 An opaque material is put between the light source and the object to diffuse the light. This
generally results in uniform illumination with condensed reflections and hot spots.

Results of Diffused Lighting

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 Transmitted Lighting

With transparent subjects the light source

is transmitted through the subject toward
the lens. The angle of the transmitted
lighting is adjusted from 90 degrees to 45
degrees for the desired effect.

Result of Transmitted Lighting

Sometimes it is necessary to pass light through an article in manner to visualize certain details.
This process is called as transmitted illumination. In the above illustration the transmitted
illumination is used to demonstrate a physical match between the two torn edges of the note.

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 Front Directional or Axis Lighting
A piece of glass is put between the subject and lens at a 45-degree angle. The light source is
positioned parallel to the film place and 45-degrees to the glass. During light transmission from
the glass, some is reflected downward on the subject. This method is effective when
photographing fingerprints on mirrors and into glasses or cups.

9. Summary
1. Making photographic records or imaging for microanalysis of different types of
evidential objects through various techniques is a challenge in forensic science.
2. Forensic Documentation often requires photographing objects such as blood spatter on
walls; footwear impressions; or innumerable small objects on the ground,
3. Instead of linking the digital camera's video output to a TV monitor, we can also attach
the video signal to a video frame grabber card, which is part of a PC.
4. Oblique Lighting uses a light source at a low angle, generally to show details by forming
shadows in the subject surface.
5. The light source is positioned parallel to the film place and 45-degrees to the glass. While
the light is transferred by the glass and some of it is reflected downward on the subject.

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 SUBJECT FORENSIC SCIENCE

Paper No. and Title PAPER No. 7: Criminalistics & Forensic Physics

Module No. and Title MODULE No. 31: Black & White & Colour Film Processing
and Printing
Module Tag FSC_P7_M31

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MODULE No. 31: Black & White & Colour Film Processing
and Printing
 TABLE OF CONTENTS

1. Learning Outcomes
2. Introduction
3. Formation of Black and White Films
4. Black and White structure and forms
5. Film Identification
6. Steps in Black and White film processing
7. Basic Requirements for Black/White film processing
8. Constitute of Black/White film developer
9. Stop Bath after film processing
10. Colour Film
11. Summary

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 1. Learning Outcomes
After studying this module, you shall be able to know –
 How Black & White and Colour Film is processed
 Learn about Black and White film formats
 Constitute of Black and White film Developer

2. Introduction
• Light striking on film causes a reaction in light-sensitive layers. The extent of the reaction is
dependent upon the amount of light hitting the film.
• Too much light will over expose the film which will make it fully black (in the extreme
case).
• Too little light will under expose the film and leave little or no image.
• An exact amount of light needs to strike the film to get the best result.
• The amount of light required is not same for all films and depends on film speed.

3. Formation of Black & White Films

Cross-section of polyester
base black-and-white
photographic film
Anti-scratch Layer: This layer protects the emulsion from physical damage.
Emulsion: This layer contains the halides which form the photographic images.

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 Adhesive Layer: This layer bonds the anti-halation and anti curl layer to the base.
Film Base: It is transparent layer which supports the image.
Anti-Curl/ Anti-halation Coating: This layer prevents the film being exposed from the rear and
stabilizes the laminate to prevent curling.

4. Black/White Structure & Forms

i. A super coat of gelatine, a few micrometres (one micrometre is 0.001 millimetre) thick,
protects the emulsion from scratches and abrasion marks.
ii. The emulsion layer (silver halide suspended in gelatine) is usually nine to 12 micrometres
(up to1/2,000 inch) thick but may sometimes reach 25 micrometres.
iii. A substrate or subbing layer promotes adhesion of the emulsion to the film base.
iv. The film base is usually cellulose triacetate or a related polymer. The thickness may range
from 0.08 to 0.2 millimetres (0.003 to 0.008 inch). Films for graphic arts and scientific
purposes are often coated on a polyethylene or other polyester support of high dimensional
stability
v. A backing layer on the rear of the film base counteracts curling. Usually it contains a nearly
opaque dye to suppress light reflection on the rear support surface. Such reflection (halation)
reduces definition by causing halo like effects around very bright image points. Some film
bases are tinted grey to absorb light that has passed through the emulsion layer.

5. Film Identification

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 A cartoon of film contains information like the
a) Manufacturer b) Type of film c) Film Speed d) No. of Exposures e) Expiry Date f)
Processing Instructions g) Storage Instructions etc.

Black & White Film Formats

35 mm films

120 films

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 Spectral Sensitivity of Black & White Film

Orthochromatic – This emulsion is sensitive from violet to green region of the spectrum and hence
can be handled in deep orange light which is safe for the film.
Panchromatic -This type of film is all colour sensitive i.e. it responds to all the colour of the
spectrum even up to ultra violet rays. So, it should be handled in complete darkness.
Infra-Red Sensitive – This type of film is sensitive from Ultra Violet to Infra Red region of the
spectrum.

Black and White Film Latitude

The latitude of a film is the amount of exposure error the user can make before the picture degrades
noticeably. Black and White Print and Colour print film have quite a high latitude ie. at least a full
stop either side of the ideal exposure may be allowed. However slide film has latitude of about 1/3
stop either side of ideal.

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 6. Steps in Black & White Film Processing
1. Working solutions of developer, stop bath and fixer to be prepared.
2. Film from the canister to be loaded in the processing spool.
3. Working solutions to be brought to the required temperature (generally 20oC for B&W).
4. A pre-wash of the exposed film in plain water at the above temperature is good.
5. The developer has to be poured in the processing tank and agitated appropriately to begin
development.
6. The developer should be poured out about 10 seconds before the appropriate development
is over.
7. Pour in the stop bath. This is pretty quick and should only take about 30 seconds - 1
minute to do its work. Pour out after the required time.
8. Pour in the fixer solution and leave for the recommended time, commonly 2-5 minutes.
Pour out after the required time.
9. Wash the film. There are several methods of doing this, but probably the easiest and
quickest if you can't wait to see the results is to fill the processing tank up and invert 5
times. Pour out and re-fill. Invert 10 times. Pour out and refill. Invert 20 times. Pour out.
10. Remove film and place a film clip at either end of the film (one to hang up and the other to
weigh down).
11. Squeegee the film to remove surplus water. Leave to dry.

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 7. Basic requirements for Black & White Processing
• Rolls of exposed Black & White film.
• Daylight type developing tank.
• Film can opener.
• Beaker or measuring cups.
• Thermometer.
• Scissors.
• Containers (of mixed chemicals).
• Negative carrier.
• 3 Containers for mixing chemicals.

8. Constituents of Black/White film developer

1 Developing The main chemical which develops the film or paper viz. Metol –
Agent (C7H10NO)2SO4, Phenidone – (C9H10N2O)

2 Preservative This chemical saves the developer from being oxidized by atmospheric
oxygen. Viz. Sodium Sulphite – Na2SO3

3 Accelerator This chemical (alkali) helps quick completion of development. Viz.

Sodium Carbonate – Na2CO3

4 Restrained This chemical stops or controls the vigorous chemical reaction and thus
protects the unexposed silver from being attacked by the developing agent
and thus stops the fog formation. Viz. Potassium Bromide - KBr .

5 Solvent All the chemicals described above are of solid form. So for homogeneous
mixing a solvent is required which is generally water – H2O.

Standard formula of B/W film Developer

The standard formula of a Metol Hydroquinone is as follows. The chemicals should be added to
water as per the order.
Metol - 2 gm
Sodium Sulphite - 60 gm
Hydroquinone - 8 gm
Sodium Carbonate - 30 gm
Potassium Bromide - 1 gm
Water - 1000 cc

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 9. Stop Bath after Film Processing
• When the film development time is complete, either throw away the developing fluid or save
for further use.
• Some manufacturers tell us about how many films each quantity of developer can process,
the numbers of cycles affect the development time.
• When the developer has been removed from the tank, the development process is abruptly
stopped by use of a stop solution.
• The stop solution is mildly acidic and neutralizes the effect of the alkaline developer. It
should be left in the tank for around a minute and then poured out, back into the storage
bottle.
•
Fixing for Non permanent Image
Development of films gives us visible images, but this will decay with re-exposure to light. So we
must fix the image by dissolving the unexposed silver halide in Hypo by making a fixer solution as
follows:-
Sodium Thiosulphate - 300 gm
Sodium Meta bisulphate - 25 gm
Water - 1000 cc
The fixing time in a freshly prepared solution is approximately 5 minutes.
• Once the solution has been stopped, the film needs to be fixed.
• Fixing prevents the black and white film from being reactive to light and any more
development process.
• It also fixes the film emulsion into transparent material leaving only the black silver oxide.
Fixing should be for around 4-5 minutes depending on the strength and age of the fixer
solution.

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 Fully developed but unfixed film Same
film Film
10. Colour after fixing

Colour film has a similar sandwich construction but is more complex due to its sensitivity to the
three primary colours, individually.

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 Instead of one layer of light-sensitive particles, colour film has three light-sensitive layers.

Black-and-white film reacts to short wavelengths, mainly light perceived as blue. If we are taking a
picture of something blue, red, and orange, the blue part would be too light, and the red and orange
part would look very dark.
So, as photographers found out about this problem, they added dye sensitizers to the film to correct
the color. Film today, is sensitive to all colors in the spectrum. Today’s film is usually coated with
three emulsions, which are usually cyan, yellow, and magenta. Each one of the emulsions is
sensitive to only one of light’s colors. With the emulsion layers, there is also a dye layer, which
makes a color that is equivalent to what a human eye sees.

How negative colour film works

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 How positive colour film works

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 Color Positive Films actually use all the subtractive color method where instead of Red Green and
Blue, it uses Yellow, Magenta & Cyan. In the Cyan, Magenta, Yellow system, the top yellow layer
is actually recording the Blue information, the middle Magenta layer records the Green information
and the bottom Cyan layer is recording the Red information. But most people relate better to RGB
color. So I will describe it that way...

Colour Negative Film Processing

The most common chemical kit out there is the C-41 Kit. It will include four easy-to-mix powdered
chemicals and according to the box, should develop 12-15 rolls of 35mm film .

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 Mixing Colour Chemicals

A narrow neck will help in keeping air out and a wide base will not let them tipping over when
working

Start by placing the chemical bottles into the hot bath. Insert a thermometer into a developing bottle
and wait till it reaches 39.5°C. This is actually half a degree hotter but it was found that in pouring
the chemicals into the developing tank, the chemicals will get cool enough to place it right on target.

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 Black & White, Colour Printing on Photographic Paper
The main major equipments required for black & white printing are the

i. Enlarger
ii. Photographic Paper
iii. Easel
iv. Developing Trays
v. Safe Light
vi. Chemicals
vii. Print Drier.
The Enlarger is a major piece of equipment for printing by means of a projector. Basically
enlarging consists of projecting an illuminated negative through suitable lens on a light sensitive
paper. An enlarger is vertical type consisting of a light house, condenser, negative carrier and
extension bellow. An even distribution of light is important so that there should not be any hot-
spot of light. When a negative is projected through an enlarger, the light loss in the corner of the
negative is balanced by the light loss of the enlarger to produce an even distribution of light. The
enlarging lens is the most important piece of equipment since the clarity of the print depends on
the capability of the lens in producing sharp image. A faster lens, a f/2.8 rather than f/4 permits
shorter exposure times and provides a brighter image for focussing.

Black & White Photographic Paper

Paper Types
Chlorobromide Paper: Used both for contact printing and enlarging. By suitable lengths of
development, tones can be varies from reddish brown to warm black. Brown safe light must be used
while handling this paper. Speed of this paper is 50% higher than chloride paper. This type of paper
has more exposure latitude than chloride paper.
Bromide Paper: It is the most light-sensitive paper. The main emulsion ingredient is silver bromide
in gelatine. It must be handled in safe light of orange.

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 All black & white photographic papers are available in different paper base like Glossy, Matt, and
Velvet, Crystal and Semi Matt. and different types of base colour like White, Cream and Yellow.
Black & White photographic papers are available in two types of thickness namely 120 gm (single
weight) and 240 gm (double weight).

Paper Grades
Ultra Soft 8 or 9 tones
Soft 7 tones
For over negatives Special 6 tones
For normal negatives Normal 5 tones
For under negatives Hard 4 tones
Ultra Hard 2 tones (black & white)

An Easel Black & White Photographic Paper

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 Paper Developer
Normal standard paper developer consists of the following ingredients:
Metol------------------------- 02 gms Dilution 1:1
Sodium Sulphite------------- 35 gms Processing Temperature 80° F
Hydroquinone---------------- 06 gms Processing Time 3 minutes
Sodium Carbonate-----------45 gms
Potassium Bromide---------02 gms
Water ----------------------- 1000 cc

Soft standard paper developer consists of the following ingredients:

Metol------------------------- 1.5 gms Dilution 1:1

Sodium Sulphite------------- 25 gms Processing Temperature 80° F
Sodium Carbonate----------- 04 gms Processing Time 3 minutes
Potassium Bromide---------0.5 gms
Water ----------------------- 500 cc

Enlargement from high contrast negatives can be developed in double bath system for better result.
In double bath system 30% over exposure is required and development should be reduced to 30%
(soft and normal developer). First put in soft developer for 1½ min and then in second developer for
1 minute. No intermediate wash is required.

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 Stop bath
This is prepared with 2% Acetic Acid in 100cc of water. It neutralizes the alkalinity of developer in
the print.
Fixer
This is prepared by mixing 250 gms of Hypo, 2.5 gms of Sodium meta bisulphite in 1000 cc of
water. Fixing time is 15 minutes in fresh solution and 20 minutes in exhausted solution.

Developing | Processing Trays (left), Tongs (middle) and Timer (right)

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 Colour Printing
In colour printing the prints are made by exposing negatives on colour paper maintaining the same
steps with the help of a colour enlarger and colour chemicals.
The primary difference between color paper developing and B&W paper developing is the
chemicals, composition of paper and temperature. Black & white emulsions have a single layer or
two almost-identical layers in the case of variable-contrast paper. Development can be done in cold
developer (slow rate) as long as the time of development is increased proportionately.
The same is not true for color development. Color papers have three layers of emulsions, each layer
responding to and developing into a different color. The main rule in color development is constant
temperature and consistent times and a completely black darkroom.
Color papers respond to all colors of light. Black & white film does too, but not B&W paper. Any
light in a colour darkroom will expose the paper, so enlargement is done in complete darkness. Once
a trial print is made, assessment fir colour cast has to be done to evaluate the print’s color. For
example, the cast may be greenish, which can be corrected by increasing the magenta filter of the
colour enlarger. Similarly a cyan cast may be corrected by increasing red which is its complementary
colour.

Illustration: Additive / Subtractive color wheel. Complementary colors (example: magenta and
green) are opposite one another.

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 At first it may be difficult to differenciate between colors, especially between red and magenta,
between cyan and blue or between yellow and green. Looking at a print (especially white areas of a
photograph or a corrected print) through colored viewing filters will help you to see what each color
looks like as a cast.

ENLARGER COLOR FILTRATION

Once we know the color and strength of the cast, it can be adjusted by filtration in the enlarger to
correct the imbalance. While it is possible to print color on a black and white enlarger by placing
individual CP or CC filters, enlargers with a dichroic head for color printing are more common.
Dichroic heads contain three filters: cyan, magenta, and yellow. Each can be adjusted separately.
Collectively, the filters are known as the colorpack.

The filtration of each color enlarger varies depending upon the type of enlarger, its age and the age
of the bulb. If we use a particular enlarger to print consistently, we can determine a good set of
values for that particular color pack and a particular brand of colour film when color correcting a
new print.

CHANGE THE ENLARGER COLOR FILTRATION

Once we have analysed the trial print’s colour cast (for example, green) adjustment through filtration
in the enlarger will neutralize that cast. The final correct print may come after two to three correction
processes.

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MODULE No. 31: Black & White & Colour Film Processing
and Printing
 REEVALUATING IMAGE DENSITY
Increasing filtration blocks light, decreasing filtration allows light to pass more easily to the print. As
a result the image density may change. As a general rule, for every 10 points of filtration you add,
add one second of time to the total exposure. For every 10 points of filtration you subtract, subtract
one second from the exposure.

11. Summary
1. Orthochromatic emulsion is sensitive from violet to green region of the spectrum and hence
can be handled in deep orange light which is safe for the film.
2. Black and White Print and Colour print film have quite a high latitude ie. at least a full stop
either side of the ideal exposure may be allowed. However slide film has latitude of about 1/3
stop either side of ideal.
3. Fixing prevents the black and white film from being reactive to light and any more
development process.
4. The primary difference between color paper developing and B&W paper developing is the
chemicals, composition of paper and temperature.

FORENSIC SCIENCE PAPER No. 7: Criminalistics & Forensic Physics

MODULE No. 31: Black & White & Colour Film Processing
and Printing
 SUBJECT FORENSIC SCIENCE

Paper No. and Title PAPER No. 7: Criminalistics & Forensic Physics

Module No. and Title MODULE No. 32: Use of CCTV for Forensic Evidence

Module Tag FSC_P7_M32

FORENSIC SCIENCE PAPER No.7: Criminalistics and Crime Scene Investigation

MODULE No. 32: Use of CCTV for Forensic Evidence
 TABLE OF CONTENTS

1. Learning Outcome
2. Introduction
3. Categories of CCTV cameras
4. Types of Cameras
5. Video Quality
6. Frames/Images Personal
7. Lens Selection
8. Surveillance Technology
9. Retrieving evidence from CCTV system
10. Video Analysis and Forensics
11. Comparing the Hash Values
12. Summary

FORENSIC SCIENCE PAPER No.7: Criminalistics and Crime Scene Investigation

MODULE No. 32: Use of CCTV for Forensic Evidence
 1. Learning Outcome
After studying this module, you shall be able to know –
 How CCTV cameras work
 Classification of CCTV cameras
 Learn about the Video analysis and Forensics

2. Introduction
Closed-circuit television, or CCTV, is a device used in home and business security systems for
electronic surveillance. CCTV cameras can help keep an eye on many different parts of a
property at the same time, and they can also help keep a record of activities or incidents. Now a
days, whenever there is an incident, whether it is an accident or a theft, police always ask or
search for CCTV footage from any nearby source that may have recorded the incident in full or
in part.
CCTV footage is one of the sources of Forensic Intelligence.

 It provides mental picture of the event for reconstruction.

 It can be used for Crime scene investigation
 Provides circumstantial evidence – clothing, bags, weapons etc.
 It can track the movement of the suspects and/or victims, both prior to and after the event.
 Trace identifiable items such as vehicle registration plates etc.
Before going for the use of CCTV footage as forensic evidence, we must understand the basics
of the CCTV camera & recording system.

3. Categories of CCTV Cameras

 INDOOR vs. OUTDOOR CAMERAS

Indoor and outdoor cameras are essentially the same in terms of style, size and shape. The
principal difference is that outdoor cameras contain some form of weather-proof housing or
case.

 NIGHTVISION AND DAY/NIGHT CAMERAS

There are two camera technology solutions in low light situation. In total darkness the only way
left is infra-red technology, which is known as night-vision.

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MODULE No. 32: Use of CCTV for Forensic Evidence
 4. Types of CCTV Cameras

i. Dome Camera
Dome cameras are a suitable choice because of their versatile dome shape. They can be placed
easily on most walls and surfaces and their round design has made it the most “fashionable” of
all security camera styles. Most dome cameras have 3 axis, hence they can be easily adjusted
once mounted. Outdoor dome cameras are available in HD and multi-megapixel resolution,
which offer day/night functionality with integrated IR illumination. Some models also feature
two-way audio and integrated memory card storage.

Features of Dome Camera:

 Dome Cameras can be installed easily– usually 2 screws are sufficient
 As Dome Cameras have an enclosed lens, the direction the camera is pointing to is
hidden
 Domes can provide infra-red for Night Vision

Simple Indoor type Dome Camera Outdoor type vandal proof

Dome Camera with IR LEDs.

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MODULE No. 32: Use of CCTV for Forensic Evidence
 ii. Box Camera

A fixed or a box camera is the most common choice for video surveillance, as they feature an
industry-standard C/CS-mount which allows them to use a variety of lenses. This makes these
cameras a fit choice for any video surveillance in commercial indoor environments. Enclosed in
a weatherproof housing, they are frequently used outdoors too.

iii. Infra-red Cameras

The distances that infra-red cameras have the capacity to see is based upon its illumination. These
cameras have LED‟s, which take out into the darkness. Realistically, a good rule of thumb is 1
foot for each LED. Therefore, if a camera has 30 LED‟s then it probably can see about 30 feet.

iv. Bullet Cameras

Bullet cameras are small. The category of internal boards and lens is limited. Accordingly, the
image excellence of the bullet cameras will not be compared with other outdated cameras, which
have double layer boards and camera function controls.
These features of outdoor bullet IR cameras are in analog format, they are the cost effective and
weatherproof, with self-contained LEDS that turn on at night, illuminating the field of view for the
camera; they are robust and self-contained, all in one. An outdoor bullet IR camera is contained in
a weatherproof case, and has built in infrared LEDs and lenses

v. Wireless Cameras
These are very popular cameras which do not need wires to connect the camera with the receiver,
and can be installed and moved from one location to the other easily. Without the wire, we can
save on installation by not worrying about lengthy or complex wire runs. Also, wireless cameras
give us the ability to incorporate video surveillance in discrete areas where other security cameras
would be difficult to place.

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MODULE No. 32: Use of CCTV for Forensic Evidence
 Since wireless is just for the video signal, we need to power the camera locally. For the most
part wireless cameras require a line-of-sight to function properly. The distance will differ
depending upon its strength i.e., transmitter and receiver. There are external wireless transmitters
and receivers that can attach to any standard camera and make them wireless, but the costs are
exceptionally high.

vi. Pan Tilt Zoom (PTZ) Cameras

Pan, Tilt, Zoom cameras cost anywhere between five – ten times the cost of a fixed camera. The
Pan, Tilt, Zoom camera will not cover or look. We cannot pan, tilt or zoom after it has been
recorded (this can only be done with a 360 degree camera). These cameras can execute many
functions which is not possible with a fixed camera. We can regulate it and also zoom in
optically up to 52x and after digitally up to 12x giving zoom abilities. The PTZ‟s have
intelligence and can be programmed to perform pre-defined tours and upon the event of an alarm
the camera can swing to a specified location before continuing its tour. An operator can dominate
and take control of the camera at any time.
These have built-in auto tracking features which makes the camera automatically track any
movement and it does so by panning, tilting, and zooming in on the subject.

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MODULE No. 32: Use of CCTV for Forensic Evidence
 vii. Hidden Cameras

They are also known as covert or spy cameras. These are security cameras which can be used for
discreet video surveillance anywhere, either indoor or outdoor as per the type and model used.
These devices can be made in the guise of common household items such as smoke detectors,
clocks, sunglasses, and baseball caps. Household items are rarely suspected of housing a video
recording device. Business houses also sometimes use hidden cameras, to keep an eye on the
employees or customers.

5. Video Quality

The producers of the CCD's mainly form 2 or 3 basic grades of products in terms of camera lines
of resolution. There is a standard resolution for color cameras (that are quoted as anywhere
between 330 TV Lines to 380 TV lines), a high resolution for color cameras (which are quoted as
anywhere between 450 TV Lines to 480 TV Lines) and a new standard some refer to as “high
definition” (which is not true high definition – that quotes of anywhere between 520 TV lines to
550 TV lines).

The more the lines of resolution in the picture, the higher the excellence of the image. Today‟s
Cameras:

High Definition (HD) – Digital/IP Camera

•720 or 1080 rows of Pixels

•Format: 16:9
•Works best with wide screens

Mega-Pixel –Digital/IP Camera

•720 or 1080 rows of Pixels

•Format: 4:3
•Allow to zoom in to small details while maintaining image integrity.

Standard Definition (SD) –Analog camera

•704 x 576 (PAL)

•704 x 408 (NTSC)
•4CIF –sufficient to meet many surveillance applications

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MODULE No. 32: Use of CCTV for Forensic Evidence
 6. Frames/ Images Per Second

Manufacturers use different expressions when identifying the speed capabilities of their products.
It will become increasingly apparent why this is misleading.

 Thirty “frames-per-second” is “real-time,” “real-motion” video in the NTSC video

standard.
 Twenty-five “frames-per-second is “real-time,” “real-motion” video in the PAL
(International) standard used in India.

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MODULE No. 32: Use of CCTV for Forensic Evidence
 This should not to be confused with “fields-per-second” (also abbreviated as “fps”).
Unfortunately, “two (2) fields” equal “one (1) frame”. So when a product states “30 fps” in its
text, is it referring to fields or frames? Is it referring to each channel of the video or the total
capability of the system? Is it referring to the system limitation or the operating capability?

7. Lens Selection

 Iris: The Iris or Aperture on the lens determines how the camera will adjust to light. It
comes in various varieties:
 Auto-Iris – It has the capability to adjust spontaneously according to lighting
conditions.
 Manual Iris - is one that you can adjust but as it states it is manual.
 Fixed Iris - means just that, it is fixed and cannot be adjusted.

8. Surveillance Technology

There are 4 type of surveillance technology to consider:

Analog type Systems PC Based DVR Stand Alone DVR IP Network

Systems System Cameras

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MODULE No. 32: Use of CCTV for Forensic Evidence
 Analog & Time Lapse (VCR based) Systems
Time lapse VCR's used for CCTV are different from the domestic machines as:
 Firstly, CCTV VCR is an industrial machine which is formed to a standard that will allow
it to run 24 hours a day.
 Secondly VCR used in CCTV systems are typically „Time-Lapse‟ machines that have the
function of stepping down or up the speed of the recording tape at slow rates.
 When using a VCR in CCTV time-lapse system it is important to realize that not all of
the frames from the camera are being recorded. For e.g. VCR in 24 hour mode only one
image in 8 images from the camera is recorded on the tape. The recording has a short
interval between each recorded image of around 1/3 sec. and this forms the jerky movie‟
type images on playback.
 24 Hour machines CCTV VCR are not famous in respect of DVR because of their
preservation that the tapes are required to be altered once a day.
 The only way we can view more than one camera on TV in a split screen mode, is by
using a multiplexer that will receive all the pictures from the cameras and split it on to the
monitor signal.

Benefits and advantages

 System is very cost effective and easy to maintain.
 Do not need any special functions.

Limitations:

 Low Video excellence in respect to the digital systems

 Highly Preserved tape should be changed every day.
 The VCR CCTV System does not have the ability for remote networking or remote
viewing.

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MODULE No. 32: Use of CCTV for Forensic Evidence
  PC based DVR
PC-based DVR is a DVR Card built inside a computer. Inside we have the motherboard,
Network card, VGA Card, CPU, Hard Drive and memory. And inside is a PCI DVR Card. This
capture board have 4,8,16 video inputs. There is a conversion of the analog signal to digital
signal and then further compression into mp4 when it is received at PC Based system. Then it
stores the data on the hard drive for archiving and playback. The DVR software offers all the
essential video and recording features, for example Video compression, changing the video to a
file, camera controls and display, record and playback functions.
It offers good quality video recording over time gap and are easier to use and more flexible than
standalone DVR's. These units are available as kits which can be installed on a PC or as
complete factory built recorders and provides with all the functionality needed for a Surveillance
system. Some models can be extended as the needs grow, which is not possible with Time Lapse
or standalone (Hardware) DVR's.
PC Based DVR available in:
· 4 Channel DVR (up to 4 CCTV camera)
· 8 Channel DVR (up to 8 CCTV camera)
· 16 Channel DVR (up to 16 CCTV camera)
· 32 Channel DVR (up to 32 CCTV camera)

 Standalone, Surveillance DVR System

Standalone DVR System is a perfect DVR solution. All function on DVR are depended on push
button or through the IR remote. Stand-alone DVR has off-site viewing function that allows to
view from anywhere in the world. With two or more internal Hard Drives and two external hard-
drive connections, recording time can be extended later in a stand-alone DVR.
Standalone DVR are computer based machines which run on Linux, Unix or other proprietary
Operating systems that were designed to run on one application only, which makes the
standalone Device a reliable appliance and does one thing only.
Benefits:

 High Resolution Recordings (720x480) or better

 Easy to operate
 Very stable and very low maintenance
 Stores large amounts of video or recording days
 Easy network integration

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MODULE No. 32: Use of CCTV for Forensic Evidence
 Limitations:

 The system runs on a proprietary operation system, which make it not flexible to standard
changes or upgrades

 IP Network Camera

Network IP Camera, often referred to as IP-Surveillance, used for for specific applications within
security surveillance, remote monitoring and Security Camera, is a system which gives users the
ability to monitor and record video over an IP network (LAN/WAN/Internet).
Unlike analog video systems, network IP camera uses the network, rather than dedicated point-
to-point cabling. The term network video refers to both the video and audio sources available
throughout the system. In cable (Coax) a network IP camera (video application), digitized video
streams are transferred to any location in the world via an IP network, enabling IP video
monitoring and recording from anywhere.

9. Retrieving evidence from CCTV system

Guidelines for retrieving digital CCTV evidence:

 A documented chain of custody must be maintained for all digital CCTV evidence
 Details related to the retrieval should be recorded including:
a. The time, date and location of data retrieval
b. The name of the operator producing the original saved record
c. Details of the recorder should be recorded, including make and model
d. Any time errors (system displayed time versus actual current time).
 Other information to record may also include:
e. Serial number of the DVR device
f. Software name and version numbers
g. Number of cameras connected versus number being recorded
h. A diagram and/ or photographs
i. The layout and location of all cameras recording to the storage device
j. Identifying the cameras responsible for the retrieved CCTV data

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MODULE No. 32: Use of CCTV for Forensic Evidence
 k. Identification and recording of output file format options and recording of the
option chosen. (Output options - i.e. optical drive, USB, Flash media or network)
l. Any usernames and passwords required to gain access to the digital CCTV
m. For remote access systems, network information, such as IP addresses should be
considered
n. Data overwrite. The current recording may need to be stopped to prevent
overwriting of the relevant digital CCTV evidence before it has been recovered
from the CCTV system
o. Players / viewing software may also need to be copied from the system

Visual verification

 Verify that the digital CCTV evidence captured as the original record is playable and is a
fair representation of what was on the CCTV system.
 If there is any visible loss in quality from what was viewed on the system, it is likely that a
compressed format has been obtained and it may be necessary to obtain the higher quality
digital CCTV evidence.
 Where practical, the native format should be obtained. However, other versions may also
be exported from the DVR or CCTV system and may be suitable for use depending on the
intended use of the data or the type of analysis required.

Storage of original copies

The original copy of the digital CCTV evidence must be made at the first opportunity before any
further processing or analysis is undertaken.

The original copy must be stored securely with write protection. For example WORM media or
an appropriately protected and backed-up mass storage system should be stored as per the
Australasian Guidelines for Digital Imaging Processes 2012.

Processing Definition
Processing is any process applied to the digital CCTV evidence where the result is primarily
visual in nature and does not require further interpretation or reporting.

General Principles

i. All processes undertaken must be valid, reliable and repeatable.

ii. Acceptable processes will vary depending on the content of the CCTV evidence.
iii. Records should be kept detailing the processes undertaken.

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MODULE No. 32: Use of CCTV for Forensic Evidence
 Guidelines

 Write protection of the original copy of the digital CCTV evidence must be considered
before making a working copy: WORM media (CD, DVD) is suitable for an original
copy
 Secure server storage, where access and write privileges are enabled to prevent
modification of the original copy, is also suitable for storage.
 Write blockers should be considered where digital CCTV evidence is stored on USB or
Flash based media.
 All processing should be completed on a working copy. The original copy should remain
secure and unedited, not modified (copying / opening file can modify it in some
instances).
 Notes of all processes and/or process settings should be recorded to ensure the process is
repeatable.
It is a good practice to work on the native files or files of the highest resolution. If lower
resolution files are used, it should be clearly stated at the beginning of any output (video or any
report), that higher resolution digital CCTV evidence is available.
Suitable processes to carry out on digital CCTV evidence may include, but are not limited to:

Transcoding (compression, format conversion)

Brightness/ contrast/ gamma etc.
Cropping / resizing
Speed adjustments
Sharpening / de-blurring
Video stabilisation
Frame averaging

10. Video Analysis and Forensics

“Video analysis is the new DNA for law enforcement. It is the next generation of
investigation”
Principles of Forensic Video Analysis
To assist in an investigation, forensic experts can repair, recover, enhance and analyze video
recordings using an array of scientific tools and techniques.
Video analysis tools can be used for previewing surveillance videos, or as an advanced tool for
enhancing low quality videos, analyzing the events in videos and documenting analysis results.
Facts about Video Forgery

With the video editing technology currently available, professionals can easily remove an object
from a video sequence, insert an object from a different video source, or even insert an object
created by computer graphics software.

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MODULE No. 32: Use of CCTV for Forensic Evidence
 However, as these techniques become increasingly available to the general public, malicious
tampering with video recordings is emerging as a serious challenge.
Although tampering with video is relatively hard, in recent years we have begin to encounter
video forgeries.
Features of Video Analysis tools
The features that are expected from a video analysis tool include the following:-
 Project management. Each case has to be is handled as a separate project, helping to
organize each requirement separately.
 Video formats and codecs. The software should contain a built-in support for large
amount of different video formats and codecs with extended support through the
Microsoft DirectShow framework. If some videos are only playable with proprietary
players, the tool should be able to import such videos using screen recording.
 Video processing filters. The tool should be able of doing operations like blocking
artifact removal, de-interlacing, histogram enhancement, noise removal, resizing,
sharpening, etc with various processing filters
 Still-image editor. Functions such as arrows, shapes, text etc. can be added to the images
or effects such as blurring, pixilation or spotlighting can be applied.
 Documentation of analysis results. The most interesting frames of case videos can be
bookmarked and annotated to better understanding of the events of interest.
 Other options, such as scripting interface, video editing, Meta data viewing, hash
calculation etc. should be included.

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MODULE No. 32: Use of CCTV for Forensic Evidence
 The tool should be able to analyse the video and show us the media information as above so that
it may be compared for the whole footage.

11. Comparing Hash Values

Hash value can be used to verify that a video file has not changed (since the previous calculation
of the hash). It should be able to calculate the hash for a given video file and compare it with the
next video file. The Result must be able to tell us if the values match.

11. Summary
1. CCTV cameras help to monitor many different parts of a property at the same time, and
they are also used to keep a record of activities or incidents.
2. Cameras are well fitted with heaters as well as blowers to respond the environment , and
other elements that can be placed in outdoor enclosure.
3. The infrared part of the spectrum has a several o technological uses, comprising target
acquisition and following by the military; remote temperature detecting; short-ranged
wireless communication and for our purposes night-vision.
4. Processing is any method applied to the digital CCTV evidence in which the result is
chiefly graphic in nature and do not need further interpretation or reporting.

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MODULE No. 32: Use of CCTV for Forensic Evidence
 SUBJECT FORENSIC SCIENCE

Paper No. and Title PAPER No.7: Criminalistics and Forensic Physics

Module No. and Title MODULE No.33: Crime Scene Photography

Module Tag FSC_P7_M33

FORENSIC SCIENCE PAPER NO.7 : Criminalistics and Forensic Physics

MODULE NO.33: Crime Scene Photography
 TABLE OF CONTENTS
1. Learning Outcomes

2. Introduction

3. Reconstructing the Crime Scene

4. Equipments for Crime Scene Photography

5. Plan of Action in Crime Scene

6. Photographing Specific Crime Scenes

7. Approach to the actual Crime Scene

8. Summary

FORENSIC SCIENCE PAPER NO.7 : Criminalistics and Forensic Physics

MODULE NO.33: Crime Scene Photography
 1. Learning Outcomes
After studying this module, you shall be able to know-

 About how to reconstruct the crime scene

 The various equipments needed for crime scene photography and also about the plan
of action at the scene of crime
 We will also learn about photographing specific crime scene and how to approach
specific crime scene

2. Introduction
The Crime Scene is the area, where a crime namely theft, robbery, loot or murder has taken
place and from which majority of the physical evidence associated with the crime is obtained.
It is concerned with the photographic documentation of evidence, crime scenes and autopsies
for investigation and presentation of an argument in a court of law. It provides investigators
with an initial point for the enquiry to define the characteristics of the questionable and
victim. Primary scene and various sites have to be thoroughly examined for the purpose.

The main thrust will be finding of some trace evidence at each scene of crime that relates to
suspect with the victim. A Crime Scene Photographer must be able to identify the target areas
where probable evidence is located and suitably capture those areas by using various
photographic techniques so that they are presentable in the court of law.

3. Reconstructing the crime scene

After the initial walk-through or survey of the crime scene, the investigator should mentally
formulate a hypothesis of the crime, focusing on the likely sequence of events and the
locations and positions of everyone present during the crime. Information like the following
may be critical in determining the truthfulness of a suspect or the reliability of a witness:

 Shoeprints may reveal a perpetrator's every step.

 Fingerprints may indicate the things the perpetrator touched.

 Tool marks may signify points of entry/exit or where safes or locked cabinets are tried
open.

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MODULE NO.33: Crime Scene Photography
  Blood spatters, bullet trajectories, the angle and severity of blows and stabs, and the
nature of the victim's injuries can reveal the actual and relative positions of the
assailant, victim, and anyone else who was present during a crime.

 The physical changes that take place in a corpse may indicate whether the body was
moved several hours after death.

The investigator should look at each piece of physical evidence to find out whether it
supports this theory, considering information obtained not only at the scene but also from the
crime lab, medical reports of anyone who was injured, and the medical examiner's autopsy
examination. Anything that doesn't fit in with or justify the investigator's theory of the crime
must be reconciled; otherwise, the theory must change. As a result, the reconstruction of a
crime scene is constantly evolving as more evidence is uncovered.

The investigator or the team repeatedly tests the increasing crime theory in contradiction of
the evidence and do not makes any assumptions although they have relevancy. An
investigator may logically believe that a piece of evidence ended up where it did because of a
suspect's actions, but if the hard evidence doesn't support this belief, the theory must be held
suspect.

If a gun is found just outside the rear door of a house where a homicide took place, logic
suggests that the assailant dropped the gun while escaping. Although that's certainly a
possibility, without solid evidence, ruling out other possibilities may be difficult. For all
investigators know, the gun had been tossed there in an attempt to make a domestic homicide
look like a murder committed by a burglar whom the victim supposedly caught in the act.
Evidence like the spouse's fingerprints on the gun or the victim's blood on the spouse's shoes
may, of course, change the theory, but until all evidence in a reconstruction is considered and
explained, investigators can't reach any absolute conclusions.

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MODULE NO.33: Crime Scene Photography
 4. Equipments for Crime Scene Photography

Crime Scene Photography Kit

The following items should be available to the crime scene photographer in order to
photograph most scenes and evidence:

 Camera
Crime scene photographers should use a high quality digital camera preferably a SLR
camera. It has at least ten megapixel and manual exposure sites (and various custom settings
in the field of ISO or sensitivity, focusing zone, exposure modes, bracketing modes, white
balance, delay timer, mirror lock, radio trigger, step aperture & shutter speed etc. are usually
suitable for crime scene and evidence photography. The body of the camera should be sturdy
and water resistant since the field of crime scene is always vulnerable to variable situation
and needs immediate action for collection of evidence.

 Normal lens
A normal lens provides the best perspective for most photographs. A 50mm lens is
considered a normal lens for a 35mm format SLR camera.

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MODULE NO.33: Crime Scene Photography
  Wide–angle lens
A wide-angle lens is required for taking pictures in small rooms or other compact areas. A 28
to 35 mm lens is considered a wide–angle lens for a 35mm camera. Recent practice is to use a
wide angle zoom from 18 to 35 mm.

 Close–up lens or close–up accessories

Most normal lenses do not focus closer than about three feet. A macro lens or a close–up
accessory for the normal lens is needed to photograph small items of evidence. Close–up
accessories include 1:1 adapters, extension tubes, bellows, reversing rings, or close–up filters.
Although scale is used, sometimes real size images of small size evidence are required.

 Filters
A polarizing filter is often really required for photographing through glass and into water.
Colored filters (red, orange, yellow, blue, and green) are used for taking pictures of several
evidences by black–and–white film.

 Electronic flash

Electronic flash, especially with TTL exposure measurement provides additional light that is
often needed when photographing indoors, outdoors at night, filling in shadows in bright
daylight scenes and for lighting evidence.

 Remote sync cord for electronic flash/ Radio Trigger

A remote sync cord allows the electronic flash to be operated when it is not mounted on
camera. Many photographs, especially photographs of certain types of evidence, cannot be
photographed with the flash mounted on the camera. Now it is possible to operate remotely
located of unconnected flash through the camera with the help of a radio trigger which are
required to illuminate a large area at night.

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MODULE NO.33: Crime Scene Photography
  Additional camera and electric flash series
Batteries can pass away deprived of cautioning at the time of documentation of a scene. For
both the camera and electronic flash, additional batteries should be carried.

 Tripod
Sturdy and lightweight tripods are necessary to make the camera rest on a stationary location
for long exposures and for positioning the camera during certain types of evidence
photography.

 Digital Storage Card

Adequate memory cards of suitable formats for the camera used with faster reading and
writing capability. Mirror copy of cards to be kept before giving it to someone without
disturbing the original card. It is important to make redundant copy of images without
disturbing the metadata.

 Photo log, notebook and pen

A photo log is necessary for recording information about each photograph taken at a crime
scene. The notebook should be carried for recording various notes regarding crime scene.

 Scales and tape measure

Different scales, containing 6 inch and 36 inch sizes should be taken for snapping diverse
kinds of objects. Long tape measures with large numbers are occasionally needed when
taking pictures of large objects of evidence or large spaces in a crime scene.

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MODULE NO.33: Crime Scene Photography
  ABFO #2 scale
The ABFO #2 scale is the preferred scale for photographing injuries. This is an extremely
essential item which judges the actual size of the evidence by seeing the image/ photograph.

 Angle–finder
An angle finder is used to help position a camera for photographing certain types of evidence
at the crime scene.

 Color chart or color control patches

Color chart or color control coverings are valuable for color mentioning the injury
photography.

 18% gray card

A 18% gray card is used as an aid in getting accurate exposures.

 Index cards and felt pen

An identifier is essential in a picture; we can give a number or identifier on an index card and
place it in the photograph.

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MODULE NO.33: Crime Scene Photography
  Flashlight
A flashlight is helpful to observe in dark areas. By shining the light on evidence from
different angles you can see where it is best to position the electronic flash for a photograph.

5. Plan of Action in Crime Scene

The main course of action includes:-

Managing a crime scene includes careful examination of the area, note taking, sketching,
photography and collection of physical evidence. The crime scene must be approached in a
methodical way and certain steps must be performed before others

There are basically 12 steps involved with the organization in a crime scene search operation-

1. Preparation
2. Approach
3. Secure and protect Scene of Crime
4. Initiate preliminary survey
5. Evaluate physical evidence possibilities
6. Prepare a narrative description

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MODULE NO.33: Crime Scene Photography
 7. Depict the Scene of Crime Photographically
8. Prepare Diagram/Sketch of Scene
9. Conduct a detailed search
10. Record and collect physical evidence
11. Conduct final survey
12. Release the Scene of Crime

SCENE OF CRIME PHOTOGRAPHY

 The well-known phrase “one picture is worth a thousand words” certainly holds true
with crime scene photography. Sciences in crime investigation could not be carried on
without Photography.

 Out of all the sciences used for Forensic investigation, photography plays a vital role
and is a visual means of communication.

Photographs constitute the single most important form of demonstrative evidence used in
Court of Law

 Before any items are moved or even touched, the crime scene should be
photographed.

 The photographs should be taken to clearly and accurately depict the scene as it was
found.

 The paths taken by the criminal to the scene, the point of entry, the exit, and the
escape route.

 Detailed photographs should be taken to show items of physical evidence in the

condition in which they were found by the investigator prior to their removal

Following items of Scene of Crime should be photographed

 The main site of the Scene.

 The route of approach of the Scene.

 The point of the entrance.

 The location and position of the Scene.

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  The evidence (injuries, weapon, hair/fibers)

 Evidence left by criminals (weapon, Bullets).

 The point of Exit and route of departure.

Admissibility of photographic evidence

1. Three major points of qualification of a photograph in court

a. Object pictured must be material or relevant to the point in issue

b. The photograph must not appeal to the emotions or tend to prejudice the court or jury

c. The photograph must be free from distortion and not misrepresent the scene or the

object it purports to reproduce

6. Photographing Specific Crime Scenes

Each crime scene has unique characteristics and the type of photographs needed will be
determined at the scene by the investigator familiar with the crime.

Specific Crimes
Each crime scene has its own particular features, and the type of photography required at
each scene will be determined by those features.

A. Homicide

Murder has been called the most heinous of crimes - the taking of another human life. It is a
curse to humanity and demands swift and satisfactory resolution. It will be important to
photograph any signs of activity prior to the murder; any evidence of a struggle, or of forced
entry if an indoor scene; and the views from the positions any witnesses had of the
crime. You will usually have to attend and photograph the ensuing autopsy, where as well as
taking photographs for your own information, you may be asked by the attending pathologist
to take photographs of anatomical significance for his information.

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 B. Suicide, other dead body calls

When attending a suicide or any other deceased for that matter, and there is some doubt as to
the circumstances of the death - treat it as a homicide. If the suicide should turn out to be a
murder you have covered it fully.

C. Burglaries

Photographs (residential or commercial burglaries)

a. Exterior of building

b. Point of entry

c. Entrance into scene

d. Interior views

e. Area from which valuable articles were removed

f. Damage to locks, safe, doors, toolmarks

g. Articles or tools left at the scene by the suspect

h. Trace evidence

i. Other physical evidence

D. Assaults, injuries

Assaults and other injury crimes firstly require a general, overall photograph of the victim
prior to detailed photographs of injuries. An assault victim can be photographed like a mini
crime scene, with general photographs, mid-range and close-up. When photographing
bruises, bites marks and other injuries close-up, use a scale to show the sizes of the injuries;
photograph at 90 degrees to the injury to avoid distortion; and use a small aperture especially
on curved surfaces such as an arm or finger to increase depth of field and so ensure the entire
injury image is sharp.

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MODULE NO.33: Crime Scene Photography
 E. TRACE EVIDENCE

Shoe and Tyre Impressions

The same principle applies as in general crime scene photography, with the photograph
showing where in the scene the impressions are located. This can be indicated with a marker
alongside the impression, which is left in position when the mid-range and close up
photographs are taken. Of course a scale is always included in the photograph as well as an
identifier with the date, location and initials thereon. It is important to keep the digital plane
of the camera parallel to the surface bearing the impression. It is equally important to use an
oblique light source to reveal the detail of the impression. When using flash in this way on
an impression which is outdoors and in sunlight, cast a shadow across the impression to
enable the flash to create a greater contrast and so reveal the detail in the impression. While a
shoe impression can be photographed in one frame, a tyre impression however needs
numerous frames which must overlap, and here it is important to have a measuring tape
alongside the impression to show the scale and to enable the photographs to be joined if
necessary.

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MODULE NO.33: Crime Scene Photography
 F. BLOOD SPLASH PATTERNS

Photographs of blood splash patterns, whether they be on a floor, on a vertical surface such as
a wall or even overhead on a ceiling, must be photographed with the film plane parallel to the
surface bearing the stain. A scale must be included on the same plane as the surface. Of
course, like any serious crime scene, general location photographs must be taken to show the
positions of the blood staining at the scene.

1. Use color film/ digital media

2. Orientation photographs to show locations of bloodstain evidence at the scene

3. Close-up photographs to show detail

a. Use a scale on the same plane as the bloodstain

b. Keep the film parallel to the plane of the bloodstain

c. Use a low oblique light angle

 MACRO/MICRO PHOTOGRAPHY

Close up of a bullet hit mark

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MODULE NO.33: Crime Scene Photography
 Foster & Freeman complete UV-Vis-IR fingerprint imaging workstation

Apart from 1:1 and 5:1 fingerprint photography other detailed photographs are often required
of tool marks, serial numbers, pieces of jewellery and the like. The focusing of a lens so close
to small objects, especially when an extension tube is used, requires the use of the smallest
possible aperture in the camera lens to ensure maximum depth of field and clarity of detail of
the item being photographed.

d. Specific types of fingerprint subjects

(1) Normal, dusted prints

(a) Usually can be photographed with no problem

(2) Impressions in soft substances (wax, putty, clay, adhesive tape, grease, etc.)

(a) Use cross lighting at an oblique angle

(b) Preview with flashlight lighting

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 (3) Porous surfaces

(a) May need to use close to a 90 degree lighting angle

(b) Preview with flashlight lighting

(4) Glass and mirrors

(a) Glass -- place white card or cloth behind glass, use low oblique angle of light

Normal Light Photograph Photograph after PolyCyano UV

one-stage chemical staining process.

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 Normal Light Photograph Photograph by Imaging Workstation

Using a combination of 3D enhancement techniques to improve the contrast and ridge

detail of a fingerprint in soft putty

ALTERNATE LIGHT SOURCES

Many lighting sources are available in forensic photography, apart from ambient daylight and
electronic flash. They include infra-red, ultra-violet, laser etc. Each has its own applications
and limitations. Their uses are mainly restricted to the crime laboratory, with the exception
of some brands which are portable and can be taken to and used at crime scenes to reveal and
enhance latent trace evidence such as fibres and body fluids. Photographing of such trace
evidence requires the use of barrier filters, and descriptions of techniques and applications
which are too detailed and comprehensive to report here.

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 Witness photograph

 Witness photographs are overall photos of the crime scene. They depict the scene as
observed by a witness.

 These photographs are designed to tell a story, to relate what the location looked like
to someone who was not present.

PHOTOGRAMMETRY

It is a science of producing 3D image from 2D object. Photography produces 2D image of 3D

object. As a result of that conversion depth of object is lost. The depth of loss cannot be
recovered from a single photograph.
However, we can compensate this depth value by taking two differently angled photograph of
the same object. By this process, a line of sight is developed. These lines, when
mathematically interpolated by triangulation process, a 3 dimensional image are produced.

The xyz data is named as .dxf data, drawing interchange file format. The .dxf data when
exported in user friendly CAD program, it produces a 3D image using i-witness &
crimezone software.

7. Approach to the actual crime scene

ROOM OF THE CRIME WITH THE OBJECTS FOUND THERE

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 ADMISSIBILITY OF PHOTOGRAPHS

 Negatives are also important if enlargements of certain areas are to be made for
comparison.

 Negatives demonstrate that the picture has not been altered.

VIDEOGRAPHY

 Videography has a great potential for the purpose and a video camcorder should be an
instrument of choice to record the Scene of Crime.

 Images should be captured in the highest quality setting of the camera with external
additional light source where the illumination is not enough.

 Large areas of the Scene can be covered showing the inter relation among the
locations and relative distance with elevation.

 Results can be played back immediately. Original video cassette or the memory cards
are to be submitted for evidence. Since no editing is accepted, the video suiting should
be made in such a way that only relevant portions are recorded crisply.

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 LABORATORY PHOTOGRAPHY

 In scientific crime detection, the camera plays a paramount importance among

laboratory instruments.

 Photographs provide a record of the initial appearance of evidence. A record of

observation made after subjecting the evidence to scientific examination.

SKETCHING

 Sketches are handy in depicting the scene of crime

 Along with Photograph, the sketches Provide idle presentation of the scene

8. Summary

1. The Crime Scene is the area, where a crime namely theft, robbery, loot or murder has
taken place and from which majority of the physical evidence associated with the
crime is obtained.
2. After the initial walk-through or survey of the crime scene, the investigator should
mentally formulate a hypothesis of the crime, focusing on the likely sequence of
events and the locations and positions of everyone present during the crime.
3. Crime scene photographers should use a high quality digital camera preferably a SLR
camera.
4. Out of all the sciences used for Forensic investigation, photography plays a vital role
and is a visual means of communication.

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MODULE NO.33: Crime Scene Photography
 SUBJECT FORENSIC SCIENCE

Paper No. and Title PAPER No.7: Criminalistics and Forensic Physics

Module No. and Title MODULE No.34: Digital Watermarking

Module Tag FSC_P7_M34

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.34: Digital Watermarking
 TABLE OF CONTENTS

1. Learning Outcomes
2. Introduction
3. Digital Watermarking
4. Incorporation of Watermarks in Digital Image
5. Significance of Watermarks in Digital Photography
6. Working of Digital Watermarks
7. Categories of Digital Watermarking
8. Image Authentication
9. Content Protection and Digital Watermarking
10. Forensics and Piracy Deterrence
11. Broadcast Monitoring
12. Summary

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MODULE No.34: Digital Watermarking
 1. Learning Outcomes
After studying this module, you shall be able to know about-

 The significance of digital watermarking

 The incorporation of watermarking to a digital image
 The various categories of digital watermarks

2. Introduction
The term “Digital Watermarking” follows the term watermarking which is believed to
have been incepted long back. Watermarks are distinguishing marks or designs or
patterns impressed on paper during manufacturing process, by making thinner (line
or wire watermarks) or thicker (shadow watermarks) on the layer of pulp when it is still
wet. Watermarks are visible when paper is held up to the light or in some cases, over a
black surface. (E.g. currency note, bond paper, stamps etc.). The objective of watermarks
in paper is, essentially identifying the paper as a signature of the manufacturer or as a
security measure to avoid forgery of important documents. The foundation of the water
part of watermark can be traced to a time when it was something which was only present
in paper. During those times, a watermark was formed by changing the paper thickness
and hence, forming a shadow or lightness in the watermarked paper. This was done while
the paper was still wet or watery and therefore the mark created by this process is called a
watermark. Undeniably, watermarks can be of help in studying the age old documents
because they can suggest their origin or date.

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 Cigarette Paper

Official Papers

Currency Notes

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 Initial application of watermarking was also information hiding for Passing Secret
messages. Information hiding started with Steganography is the art and science of
concealing messages into something innocuous in such a way that it is extremely difficult
for someone to suspect, let alone find, except intended recipient knows of the existence of
the hidden message.

3. Digital Watermarking

Digital watermarking is the process by which identifying data is woven into media
content such as images, movies, music or other multimedia data with a specific algorithm
imparting the objects with an exceptional, digital identity which can therefore be used in
various applications. Though a digital watermark is indiscernible to the human senses and
nevertheless simply documented by special software detectors, it remains constant even
after being recorded, manipulated and edited, being compressed or decompressed,
encrypted, decrypted and broadcasted, without the content quality being affected. A
digital watermark added to a photo, is more or less visible information in the form of a
text or some other photo/image that has been added to the original photo. The added
information can be more or less transparent to make it either easy or hard to notice the
watermark.

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MODULE No.34: Digital Watermarking
 So a digital watermark is a lot like the metadata that is invisible and attached to an image.
Unlike metadata, it is much more difficult to remove and it stays with an image even
through all types of manipulation like copying, cropping, editing, compression and
decompression, encryption and decryption without affecting the quality of the image.

4. Incorporation of Watermarks in Digital Image

In a photograph the addition of a transparent watermark is done by changing the image at

the level of pixel wherein a pixel represents one dot of an image. The pixels that will
make up the resulting watermark is changed more or less in the direction of the
watermarking image, if for example the watermark is 50% transparent, 50% of the RGB
(Red, Green & Blue) values are deducted from the original image, and 50% of the RGB
values from the watermark are added to the image.

5. Significance of Watermarks in Digital Photography

A watermark is added on a digital photograph with the intention that it should not be
copied or used without the consent of the author or the originator. Also if a highly visible
watermark is added along with an almost hidden one, it will be much more easy for the
thief to overlook the invisible and thereby adding more protection of the images.

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MODULE No.34: Digital Watermarking
 A lot of research has been carried out so that an invisible watermark can be added to the
image which is difficult to remove again; many of these programs do not work on JPEG
images since these are transformed in the compression of the image. Many companies are
working on the option of adding a hidden watermark to the image.

Digital watermarking algorithm is of three parts:

a. Watermark embedding algorithm

b. Watermark extraction algorithm
c. Watermark detection algorithm

Digital watermarking is a technology that opens new door for users, whether watermark
can be reliably detected after performing some media operations.

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 i. Perceptual transparency

This property describes that whether watermark is visible or invisible to human sensor
organ. Perceptible watermarks are defined as those watermarks which are visible to the
human sensory organ. The imperceptible watermarks are defined as those watermarks
which cannot be visualized and in these, the contents remain unchanged even after the
application of the technique of digital watermarking. Perceptible watermarks i.e. visible
one are extension of the concept of logos. They are applicable to images only. These
watermarks are embedded into image. They are applicable in maps, graphics and software
user interface. Imperceptible watermarks are useful for content or author authentication
and for detecting unauthorized copier.

ii. Security
Security property describes that how easy to remove a watermark. This is generally
referred to as “attack” on watermarking. Attack refers to detection or modification of
watermark.

iii. Complexity
This is an important property which is to be considered in Real time applications like
video. Complexity property is concerned with amount of effort needed to extract or
retrieve the watermark from content.

iv. Capacity

Capacity property of digital watermarks refers to amount of information that can be

embedded within the content. If more data is used in watermark, it will become less robust.

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 v. Robust watermarks and fragile watermarks

Robust or fragile is the degree wherein a watermark is able to withstand any sort of change
which is caused because of lossy or transmission compression. The imperceptible
watermarks are less robust as compared to the perceptible one. Robust watermarks are
defined as those watermarks which when embedded in an object are difficult to remove
whereas fragile watermarks can be defined as those which can easily be destroyed, if any
tampering is done with them. Also, once there is manipulation of data, the fragile
watermarks will get destroyed by it.

vi. Private watermarks and public watermarks

Private watermarks need at least unique data to improve watermark information. Public
watermarks require no real data and implanted watermarks to pull through watermark
information. Private watermarks are also known as secure watermarks. To read or retrieve
private watermark, it is essential to have secret key. Public watermark can be read or
retrieved by anyone using specialized algorithm.

6. Working of Digital Watermarks

Digital watermarks offer the way of escaping steganographic messages for many different
purposes.

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 • Data (D), Watermark (W), Stego Key (K), Watermarked Data (Dw)

Embed (D, W, K) = Dw

Extract (Dw) = W‟ and compare with W

(E.g. find the linear correlation and compare it to a threshold)

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  How do we make this system secure?

A. Stego Key or K is secret (Use cryptography to make information hidden more

secure)

Example – Embedding (DW = D + W)

• Matrix representation (12 blocks – 3 x 4 matrix)

(Algorithm Used: Random number generator RNG), Seed for RNG = K, D =

Matrix representation, W = Author’s name

Example – Extraction

• The Watermark can be identified by generating the random numbers using

the seed K

Data Domain Categorization

• Spatial Watermarking

Through application of data to implant and remove Watermark

E.g. voltage values for audio data

• Transform Based Watermarking

Conversion of data to another format to embed and extract.

E.g. Transformation to polar co-ordinate systems of 3D models, creates it forceful against
scaling

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 Extraction Categorization

• Informed (Private) : Extract using {D, K, W}

• Semi - Blind (Semi-Private) : Extract using {K, W}

• Blind (Public) : Extract using {K}

- Blind (requires less information storage)

- Informed techniques are more robust to tampering

Robustness Categorization

• Fragile (for tamper proofing e.g. losing watermark implies tampering)

• Semi-Fragile (tough in contradiction of operator level processes, e.g. image

compression)

• Robust (counter to challenger grounded attack, e.g. noise possession to images)

Categorization of Watermark

Eg1. Robust Private Spatial Watermarks

Eg2. Blind Fragile DCT based Watermarks
Eg3. Blind Semi-fragile Spatial Watermark

7. Categories of Digital Watermarking

Spatial Domain Method

The spatial domain is the normal image space, in which a change in position in I directly
projects to a change in location in space. Distances in I (in pixels) relate to actual
distances (e.g. in meters) in space. This notion is most often used while taking into
account the frequency at which the value of image changes, i.e. when does the repeating
intensity variations occur depending upon the pixels.

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MODULE No.34: Digital Watermarking
 Transform Domain Method

High quality watermarked image is produced by this method in which the original image
is first transformed by use of DCT or Discrete Cosine Function, DWT or Discrete
Wavelet Transform and Fourier into its frequency domain. Thus, in this method the
marks are added to the values of its transformed coefficients and not to the image
intensity. The watermarked image is formed by inversing the marked transformed
coefficient. The use of frequency based transforms allows the direct understanding of the
content of the image. Hence, HVS or features of the Human Visual System (HVS) can
then be consider when it is phase to select the concentration and location of the
watermarks to be made functional to a given image.

Least Significant Bit

The easiest method in digital watermarking is in spatial domain applying the two
dimensional display of pixels in the container image to hold hidden data using the Least
Significant Bits (LSB) method.

The stages to insert watermark image are given below.

Steps of Least Significant Bit

 Transform RGB image to gray scale image.
 Create twin exactness for image.
 Shift most significant bits to low significant bits of watermark image.
 Create less noteworthy bits of host image to zero
 Enhance cleaned version of watermarked image to altered host image.

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 Limitations of Spatial Domain Watermarking

In any watermarking application, this method lacks robustness and is relatively simple. In
addition to the noise factor, it can also survive simple operations like cropping but the
watermark is defeated by the lossy compression. To have negligible impact on the cover
object the LSB bits can then be set to „1‟ and moreover, the watermark can be altered by
an intermediate party once the algorithm is discovered.

Discrete Cosine Transform Watermarking

The DCT permits an image to be fragmented into dissimilar frequency bands, making it
very easier to insert watermarking information into the middle frequency bands of an
image. The middle frequency bands are selected so that they have diminished, they
escape the most graphic imperative portions of the image devoid of over-exposing
themselves to removal through firmness and clatter attacks.

Steps of DCT watermarking

The elementary notion in the DWT for a one dimensional signal is that a signal is divided
into two portions, generally high frequencies and low frequencies. This procedure is a
continuous chance of number of intervals, which is generally known by the applying at
instance.

Steps of DWT watermarking

i. The main measure of the watermarking process is, basically the encoder. The first
stage is to molder the image into 4 frequency bands by applying first purpose of
Haar wavelets at this state.

ii. In succeeding phase, molder image into 7 frequency bands by applying

subsequent resolutions of Haar wavelets. At next level, molder image in to 10
frequency bands by applying third resolutions of Haar wavelets and so on.

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MODULE No.34: Digital Watermarking
 iii. The afterward process is to give a pseudo arbitrary sequence N, Gaussian
distribution of mean zero and variance one, to the coefficients of the medium and
high frequency bands.

iv. The normal distribution is used because it has been proven to be quite robust to
collusive attacks.

Digital Watermarking Applications

 Copyright Protection: To prove the ownership of digital media.
 Hidden watermarks represent the copyright information.
 Tamper proofing: To find out if data was tampered. Eg. Change meaning of images.
 Hidden watermarks track changes in meaning.

8. Image Authentication

At first, a semi-fragile watermarking in embedded into the image for authentication and
reliability inspection resolutions by applying a QIM scheme assimilated in a JPEG2000
coder next, the image is JPEG compressed at default quality level (in order to simulate a
common unintentional attack) and then maliciously manipulated using the Gimp.

9. Content Protection and Digital Watermarking

It offers an additional sheet of safety to the content protection chain to deter unauthorized
use of content by inserting watermarks that recognize the acceptable application of the
content into the music or motion picture soundtrack prior to theatrical, packaged media
(Blu-ray Discs, DVDs) and online digital distribution.

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MODULE No.34: Digital Watermarking
 10. Forensics and Piracy Deterrence
Forensic watermark tool applied to improve a content possessor's capability to perceive
and reply to mismanagement of its possessions. Forensic watermarking is applied not
only to collect evidence for legitimate measures, but also to impose prescribed usage
contracts between a content owner and the individuals or corporations with which it
shares its content. It offers progressive, irrefutable evidence of misuse for leaked content
assets. Watermarking can also counterpart Digital Rights Management (DRM), by
harmonizing content proprietor patents with customer reasonable use allowances.

Working procedure

A forensic application embeds the identity of a recipient into an asset copy (Forensic
Report) at the time it is produced or transmitted. Sophisticated forensic advantage insert
situational metadata like as broadcast time, received format, and recipient IP address.
Some watermark applications embed a distinct forensic watermark at each stage of
content distribution, enabling pinpoint accuracy. When a leak is discovered or suspected,
the forensic watermark retrieved from the leaked copy identifies the intended recipient
and provides evidence in the form of situational metadata that the copy was delivered to
its intended destination. The evidence can be used to trigger contractual provisions or as
legal evidence in a criminal action.

Use of digital watermarking for forensics & piracy deterrence helps

companies

 Create a powerful deterrence from leaking content either maliciously or

unintentionally.
 Quickly and accurately identify the source of leaked content.
 Provide irrefutable evidence of content misuse in support of legal action.
 Gain visibility over where and how their content is being accessed without the need
of a complete DRM system to restrict access.

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MODULE No.34: Digital Watermarking
 Content Filtering (includes Blocking and Triggering of Actions)

The experience of watching television has radically changed over the last few years.
Today people want to watch content in their own time and place. Digital watermarks
offer new opportunity for content possessors, promoters and very commonly marketers
who are in search for innovative methods to engross customers with richer media
experiences from the STB and Television set.

Copyright Communication and Digital Watermarking

Watermarks stay with content as it is forwarded and travels across the internet and can be
detected at any point to determine the content's unique identity. Watermarks also persist
in various diverse file managements and conversions, contrasting usual metadata which is
frequently missing, making the content "orphaned."

Effective copyright communication helps content owners

 Ensure their ownership and contact information stays permanently attached to their
content wherever it may travel and be accessed on the web or packaged media.
 Monetize their content, with opportunities to add automated licensing to increase
revenues.
 Better managing of content through a range of automated remedies when
unauthorized use is discovered, including device enforcement messages of copyright
policies, take down notices or providing permission with proper attribution.
 Protect their content from being an "orphaned work" whose origin is unknown.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.34: Digital Watermarking
 Document and Image Security and Digital Watermarking

Digital watermarking enables corporations and brand owners to embed a unique digital
ID into confidential documents and digital images. For instance, a unique digital
watermark can be easily embedded into each copy of a confidential document as they are
being created and distributed. The data contained in the watermark can include who the
recipients are of each copy so that any information that is inadvertently or intentionally
leaked out is easily traced back to the source. Finally, watermark detectors can be
included in various printers, scanners and other devices to check for watermarks in
confidential documents that someone is attempting to copy.

Effective document and image security helps companies

 Identify each copy of a confidential document and/or image with a unique digital
identity.
 Trace back to the source of leaks if sensitive materials are distributed intentionally
or inadvertently.
 Filter documents being uploaded to the web or forwarded in email to quickly
identify confidential materials and stop distribution.
 Prevent the copying of confidential documents on copiers and/or scanners.

Authentication of Content and Objects (includes Government IDs)

The impact of counterfeiting is significant, both in terms of lost revenue for businesses
and fraud to the consumer, which can even endanger citizens in the case of counterfeit
pharmaceuticals. When used as part of a linked and layered security approach, can
provide a strong and effective deterrence to counterfeiting and help to solve this costly
and challenging problem.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.34: Digital Watermarking
 Effective authentication of content, IDs and objects helps companies
 Reliably authenticate documents, objects and personal IDs at points of inspection.
 Ensure that shipments travel their intended route and arrive at the proper
destination.
 Immediately identify possible tampering or counterfeiting when the watermark is
absent.

11. Broadcast Monitoring

Over the last few years, the number of television and radio channels delivering content
has notably expanded. And the amount of content flowing through these media vehicles
continues to grow exponentially.

Digital watermarking helps content owners and copyright holders to-

 Estimate the accurate range of media effects.

 Approve and verify content transmission and application.
 Determine contractual compliance.
 Immediately identify new sales opportunities.
 Identify potential misappropriation of assets.
 Communicate content rights and intent.

Digital watermarking helps broadcasters and agencies to-

 Authenticate bonds and invoices for eventual exactness and responsibility.

 Diminish in-flight incongruities by refining media stewardship.

Digital watermarking helps key broadcasters and networks to-

 Electronically verify affidavits/invoices.

 Replace electronic or manual affidavits/invoices.
 Compare schedules versus detections for faster invoice development.
 Report or electronically transmit available affidavit/invoice databases.

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MODULE No.34: Digital Watermarking
 12. Summary
 The objective of watermarks in paper is, essentially identifying the paper as a
signature of the manufacturer or as a security measure to avoid forgery of important
documents.
 Physical steganography has been in use since ancient times and included invisible
ink, Morse code on knitting yarn which was then made into garments, microdots,
messages on the back of postage stamps and more.
 Digital watermarking enables corporations and brand owners to embed a unique
digital ID into confidential documents and digital images.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.34: Digital Watermarking
 SUBJECT FORENSIC SCIENCE

Paper No. and Title PAPER No.7: Criminalistics and Forensic Physics

Module No. and Title MODULE No.35: Legal Aspects of Visual Evidence

Module Tag FSC_P7_M35

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.35: Legal Aspects of Visual Evidence
 TABLE OF CONTENTS

1. Learning Outcomes
2. Introduction
3. Historical Foundation
4. Accuracy of Color
5. Computer Generated Images
6. Inflammatory Photographs
7. Marking Photographs
8. Misleading Photographs
9. Optical Illusion
10. Presentation Strategy
11. Summary

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.35: Legal Aspects of Visual Evidence
 1. Learning Outcomes
After studying this module, you shall be able to know about-

 Know about legal aspects of visual evidences

 Learn about computer generated images

2. Introduction

Because it is often impractical, if not impossible, to take the jury to the scene of the crime
or incident, the next best alternative is to bring the scene into the courtroom. For more
than a century, the best method has been photographic documentation of the scene.
Forensic photography is the accepted methodology, and because of its success, the legal
foundation for admissibility has been significantly simplified. There are two basic
requirements for the admissibility of photographs. First, someone must have personal
knowledge to testify as to the accuracy of the depiction of the subject in the photograph.
Second, someone must identify the equipment used as well as its capability of producing
a true and accurate representation. In recent years, it has been my experience that this
process has become less complex. Generally, all that is required is confirmation by a
witness that he saw the object or subject at the scene and, further, that the photographic
documentation is a fair and accurate representation.

3. Historical Foundation
For the most part, the requirement for accurate photographic representation includes
photographs, slides, videotapes, movies, and x-rays. The acceptance of this broad
medium as evidence in court has been well established. The first photographs
(Daguerreotypes) were used in a civil case by the Supreme Court in Lucy vs. United
States, 23 Howard 515 (1859), to decide the authenticity of photographs in comparing
signatures. The first recorded criminal case introducing photographs as identification
evidence was Udderzook vs. Commonwealth, 76 Pa. 340 (1874).

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.35: Legal Aspects of Visual Evidence
 Color photographs were introduced in civil litigation in Green vs. City and County of
Denver, 3 Colo. 390, 142 P.2d 277 (1943), involving color photographs of spoiled meat
in violation of the health ordinance prohibiting the sale of putrid meat to the public.
Criminal cases have shown the importance of color since the 1960s, in a case that
depicted the graphic wounds of the victim, State vs. Conte, 157 Conn. 209, 251 A.2d 81
(1968). Slides have been notable State vs. Sheppard case, 100 Ohio App. 34.1,.128 N.E.
2d 471 [‘1’ upheld in a rehearing, 352 U.S. 955 (1956)]. Color slides depicted the
victims. Motion pictures were accepted in 1916, Duncan vs. Kieger 6 Ohio App. 57. The
use of videotapes as evidence of defendants statements and confessions has been upheld
as early as 1969, Parramore vs. State, 229’s 855 (Fla., 1969).

4. Accuracy of Color
The true color reproduction may be a point of contention if the color is a critical issue.
Questions may be directed at the lighting, filters, and processing, any or all of which can
alter color balance. Use of a standard color balance bar in the corner of the photograph
allows comparison with the original bar used to produce the photograph. Alterations of
Negatives and Prints any deliberate attempt to alter the photographic evidence is
inexcusable and) to the untrained eye, difficult to detect. Usually the deception is one of
two types. One is eliminating evidence such as scars, cracks, or defects from photographs
by filtering. The second is through the use of double exposure. Objects or people can be
added to a photograph with multiple negatives. Careful scrutiny of the highlights and
shadows in the photograph or negative can reveal these attempts at deception.

5. Computer Generated Images

Today’s computer technology brings with it new enhancement capabilities to apply

problems photographs. It also brings the chance of mis-understanding because of many
individuals fears of the unknown. It is imperative that supporting testimony from the
computer imaging expert provides the proper foundation for acceptance of this type of
evidence.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.35: Legal Aspects of Visual Evidence
 6. Inflammatory Photographs

Photographic documentation that shows graphic details of gruesome wounds, injuries, or

deceased victims may raise objections on the grounds that it may prejudice the jury. The
relevancy and factual content are important to the admissibility of graphic photographic
evidence. Nudity is another area where proper foundation will avoid unnecessary
objections. In a series of rape assaults on college women, the photographic
documentation of puncture wounds to the breasts was admissible based on the fact that
the weapon (a sharpened screwdriver) responsible for wounds inflicted on four different
women was a common modus operandi of the defendant.

7. Marking Photographs

The use of a particular photograph to emphasis a point with more than one witness is
often done by marking the photograph. Thus marks may consist of lines, arrow, numbers,
circles and so forth to draw attention to a particular point in the paragraph. To preserve
the integrity of the photograph, it may be helpful to use clear acetate overlays on which
the witness can make their marks. Another method would involve duplicate points of the
subject on to be used for marking by the witness.

Another type of mark that may be objectionable is a defect in the negative that produces
artifacts on the point. These marks can appear on light or dark spot on even clouded
images. If the photograph is critical, it will be necessary to produce the negative for
review by your adversaries. The computer their argument that it is not a true and accurate
representation you might point out that no photograph is an exact representation
considering that it is only two dimensional.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.35: Legal Aspects of Visual Evidence
 8. Misleading Photographs

In addition to objections that arise over color, optical distortions, markings or time lapse
are several other areas relevant to objectionable content of photographic documentation.
Some photographs may be confusing to a juror if necessary or irrelevant objects are
crowding the photograph. Like-wise, if the photograph is taken too close, segregating the
object from the rest of the scene, it can be just as misleading. Therefore, it is suggested
that additional overall photographs be taken for orientation to the overall picture.

A single photograph portraying one point of view, particularly when related to subject
material over a period of time, could be misinterpreted by jurors. For example, an
intersection where a pedestrian vehicle accident occurred as shown in a photograph as
having relatively high pedestrian traffic. The correct photographic series shows that
actual time frame when the incident occurred some three to four hours later than the
single photograph of the same intersection.

Photocopies (sometime referred to as laser copies) produced on color photocopying

machines appear as very good likenesses at first glance. However, the limited quality of
color shading is most noticeable and the paper (typically bond) cannot compare with
photographic paper.

9. Optical Illusion

Avoid using excessively wide-angle lenses (greater than 28 mm), which create fishbowl
distortions at the edges of photographs. Telephoto/zoom lenses are useful in many
instances, for example, in surveillance, where close-up identification is desirable, but
subjects in the foreground must be avoided, as they can detract from the objective by
appearing closer in the photograph than they actually were. Also, consider the
composition of your photograph in relation to accuracy. Vertical lines will appear longer
than horizontal lines of the same length. Lighter-shade objects will appear larger than
dark objects. If the photo-graph is to fall within the guidelines of a true and accurate
representation, do not let distortion detract from your objective to present the truth.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.35: Legal Aspects of Visual Evidence
 Scale of Reference

When the photographic evidence portrays size or distance, it is suggested that two
photographs of the same subject be taken — one as it is found and a second with a scale
of reference. The scale can be a standard ruler, yardstick, tape measure, or specifically
designed rule, usually six to seven inches in length, marked in both inches and
millimeters and blue or gray in color. A scale of reference photographed with bloodstain
evidence is far more effective in differentiating between high-velocity (diameter less than
1 mm) and cast-off blood spatter.

Sight Perspective

If the photograph depicts an observation made by a particular witness, be sure the

photograph was taken from that person's perspective. It is important to take the
photograph as near as possible to the same angle and eyesight level as the witness. This is
particularly important in motor vehicle accidents, in which the sight perspective of a
driver or pedestrian can be very important because of any obstructions.

Time Frame

The lapse of time between the event and when the photographs were taken is subject to
objection based on time of day, weather conditions, time of year or changes of
appearance in the scene caused by actions of individuals (moving furniture in a room,
construction or demolition of buildings, etc.).

If a substantial period has elapsed, additional care may be required to lay the foundation
for admission of the photographs as relevant. The witness must show that the photograph
is fair and accurate in aiding his testimony.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.35: Legal Aspects of Visual Evidence
 10. Presentation Strategy

The primary purpose of photographic evidence is to aid the jury in relating witness
testimony to other forms of physical evidence. The objective in preparing demonstrative
evidence for court is to have it viewed by jurors while testimony is given. All too often
the photographic evidence is taken for granted, and the normal 3 X 5 prints are passed
among the jurors during testimony. Not only is this confusing to the jurors, but it can be
very distracting to the witness. There are several alternative techniques to maximize the
effectiveness of photographic evidence.

Enlargements are routinely accepted. Occasionally, a juror will stop for a moment or ask
to point out the subject addressed. Such evidence stays with them long after you have left
the court-room and they have retired to deliberate. The original print (and sometimes
negatives) should also be available for comparison of content and accuracy.

An alternate technique with enlargements is to mount poster-size photographs on a stiff

backing material (form-core board, illustration board) and display them on an easel near
the jury. The witness can then direct juror’s attention to points of interest during
testimony. The disadvantage is the lack of personal contact with the jury developed with
the previous technique.

Presentation of slide transparencies in court has become widely accepted. The advantage
of a large photograph directing everyone’s attention to one visual display at a time may
be outweighed only by problems with courtroom dynamics. Older courtrooms may not
allow adequate darkening for proper viewing of slides. More recent courtroom design,
however, has provided for proper room darkening as well as strategically mounted
screens for optimum viewing. An important footnote to proper preparation is always have
a backup projector and spare bulbs for the unexpected failure. One additional suggestion
for the convenience of the jurors, have a set of prints made from the slides that can be
passed around later during deliberation.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.35: Legal Aspects of Visual Evidence
 Modern photographic documentation brings the technology of video tape into the
courtroom with ever-increasing frequency and great success. When properly prepared
and introduced, nothing is closer to the truth than a moving documentation, particularly
with audio backup. It is as close to lifelike as our technology has come, keeping
everyone's attention directed to one subject at the same time.

The latest introduction to the field of demonstrative evidence is computer graphic

enhancement of photographic images. This technique, while relatively new in its
application to the area of forensic photography, has been accepted in several judicial
proceedings. It is important to lay proper foundation for the accuracy of the work and the
expertise of the individual who produced the work. The three-dimensional capabilities of
this medium hold tremendous promise for the areas of accident and crime scene
reconstruction.

11. Summary

1. The technology of modern photographic equipment has significantly reduced the

margin of error in producing court-acceptable photographs.
2. If you read the owner’s manual provided with camera, use the suggested film speed
(ISO), and practice, you should encounter little concern about the acceptability of your
work in court.
3. There are time and situations where special techniques for photographing evidence
may require additional testimony to lay the foundation for its admissibility. The need
may arise for additional explanation of methodology, equipment, and technician’s
experience. This is often the case with techniques such as microscopy,
macrophotography, ultraviolet photography, photogrammetry and videography.
4. When properly prepared and introduced, nothing is closer to the truth than a moving
documentation, particularly with audio backup. It is as close to lifelike as our
technology has come, keeping everyone's attention directed to one subject at the same
time.

FORENSIC SCIENCE PAPER No.7: Criminalistics and Forensic Physics

MODULE No.35: Legal Aspects of Visual Evidence