SUBJECT FORENSIC SCIENCE
Paper No. and Title PAPER No.12: Forensic Biology and Serology
Module No. and Title MODULE No.3: Nature and Role of Forensic Biologist in
Crime Scene Investigation
Module Tag FSC_P12_M3
FORENSIC SCIENCE PAPER No.12: Forensic Biology and Serology
MODULE No.3: Nature and Role of Forensic Biologist in
Crime Scene Investigation
TABLE OF CONTENTS
1. Learning Outcomes
2. Introduction
3. Protection of Crime Scene
4. Recognition of Biological Evidence
5. Searches
6. Collection of Biological Evidence
7. Role of Forensic Biologist
8. Skills of Forensic Biologist
9. Summary
FORENSIC SCIENCE PAPER No.12: Forensic Biology and Serology
MODULE No.3: Nature and Role of Forensic Biologist in
Crime Scene Investigation
1. Learning Outcomes
After studying this module, you shall be able to know-
How to Protect, Recognize, Search & Secure the Biological Evidences in
Crime Scene Investigation
Nature and Role of forensic biologist in conducting investigation of the crime
scene
2. Introduction
Forensic biology is a sub-discipline of forensic science.
Forensic biology uses scientifically accepted protocols to analyse biological evidence.
Laboratory analysis utilizes scientific techniques for the examination of evidence, the
reconstruction of a crime scene, the identification of biological fluids, and the
comparison of individual characteristics of biological evidence.
Forensic investigation involving biological evidence usually begins at the crime scene.
The crime scene investigation process includes maintaining scene security, preparing
documentation, and collecting and preserving physical evidence. A crime scene
investigation requires teamwork and effort. Each team member should be assigned
specific tasks.
FORENSIC SCIENCE PAPER No.12: Forensic Biology and Serology
MODULE No.3: Nature and Role of Forensic Biologist in
Crime Scene Investigation
3. Protection of Crime Scene
A crime scene investigation begins with the initial response to a scene. Securing and
protecting the scene are important steps in a crime scene investigation and this task is
usually carried out by the first responding officer arriving on the scene. The entry of
authorized personnel admitted to the scene should be documented using a log sheet.
Suspects, witnesses, and living victims should be evacuated from the scene. If a victim
is wounded, medical attention should be sought.
Appropriate supplies and devices should be used to prevent the contamination of
evidence by investigators. Protective wear and devices including a face mask or shield,
safety eyeglasses, a disposable coverall bodysuit, gloves, shoe covers, and a hairnet
should be used.
Exposure to bodily fluids may occur during a crime scene investigation. An
investigator can be exposed to bodily fluids through the mucous membranes, skin
exposure, and needle-stick injuries (especially when investigating a clandestine drug
laboratory scene). Therefore, biosafety procedures must be followed for the protection
of personnel from infectious blood-borne pathogens such as the human
immunodeficiency virus (HIV), hepatitis B virus (HBV), and hepatitis C virus (HCV);
infectious aerosol tuberculosis pathogens; and other bio-hazardous materials.
4. Recognition of Biological Evidence
A preliminary survey should be carried out to evaluate potential evidence. In
particular, the recognition of evidence plays a critical role in solving or prosecuting
crimes. The priority of the potential evidence at crime scenes should be assessed based
on each item’s relevance to the solution of the case. Higher priority should be assigned
to evidence with probative value to the case.
FORENSIC SCIENCE PAPER No.12: Forensic Biology and Serology
MODULE No.3: Nature and Role of Forensic Biologist in
Crime Scene Investigation
For example, the evidence related to a corpus delicti is considered to be of the highest
priority. Corpus delicti is a Latin term meaning “body of crime.” In Western law, it
primarily refers to the principle that in order for an individual to be convicted, it is
necessary to prove the occurrence of the crime. In a forensic investigation, it also
refers to the physical evidence proving that a crime was committed. For example,
when an individual is missing, a missing person investigation is usually initiated.
If corpus delicti, such as a dead body or a victim’s blood at a crime scene, is
discovered during the investigation, a homicide case can be established and a suspect
can be charged with homicide. Higher priority should also be attached to evidence that
can establish connections such as victim-to-perpetrator linkage. For example, items
found in a perpetrator’s possession may be linked to a victim.
This also applies to transfer evidence based on the principles of transfer theory, also
known as the Locard exchange principle, which theorizes that the cross-transfer of
evidence occurs when a perpetrator has any physical contact with an object or another
person. Thus, trace evidence, such as hairs and fibers, may be transferred from a
perpetrator to a victim or vice versa. This explains why it is important to ensure that
perpetrators and their belongings are thoroughly searched for trace evidence.
Likewise, victims and their belongings should be examined for the same reason.
Victim-to-scene and perpetrator-to-scene linkages can also be established. Blood
belonging to a perpetrator or a victim found at a crime scene can establish such a
linkage. Additionally, reciprocal transfers of trace evidence from crime scenes can be
used to link a suspect or a victim to a crime scene.
FORENSIC SCIENCE PAPER No.12: Forensic Biology and Serology
MODULE No.3: Nature and Role of Forensic Biologist in
Crime Scene Investigation
A perpetrator may present a unique modus operandi (MO). Modus operandi, a Latin
term commonly used in criminal investigations, refers to a particular pattern of
characteristics and the manner in which a crime is committed. For example, Richard
Cottingham, a serial killer known as “the torso killer,” dismembered his victims and
took their limbs and heads with him but left their torsos at the scene. He then set the
rooms on fire before fleeing the scenes. Evidence that provides information on the MO
is also vital to an investigation. A distinct MO can establish a case-to-case linkage for
serial offender cases.
5. Searches
Some investigations require a search for specific items of evidence such as biological
stains, human remains, and all relevant evidence. A search usually has a specific
purpose. Thus, the use of search patterns can be helpful, especially in cases involving
large outdoor crime scenes.
Search patterns may include a grid, line, or zone. The method that is ultimately used
depends on the type and size of the scene. Additionally, the points of entry and exit
and the paths followed by a perpetrator should also be searched. Searching for
biological stains usually utilizes devices such as an alternate light source (ALS). An
ALS either produces a single specific wavelength of light or a desired wavelength by
using specific filters. Biological materials such as blood, semen, and saliva emit
fluorescent light under an ALS, which can facilitate the locating of biological
materials. Additionally, field tests and enhancement reagents can be used to facilitate
crime scene searching. These reagents can detect and identify biological evidence. The
tests are very simple, rapid, and sensitive, and thus can be used at crime scenes. For
example, phenolphthalein and leucomalachite green tests can be used for detecting
blood evidence.
FORENSIC SCIENCE PAPER No.12: Forensic Biology and Serology
MODULE No.3: Nature and Role of Forensic Biologist in
Crime Scene Investigation
Sometimes, minute amounts of blood may be present at the scene as a result of
attempts to clean up blood prior to the investigation. These stains may not be visible
with the naked eye. Enhancement reagents such as luminol and fluorescein, which
emit chemiluminant and fluorescent light upon reacting with certain biological
materials, respectively, can be used. Additionally, the enhancement reagents can detect
faint blood-containing pattern evidence such as faint bloody fingerprints, footprints,
and other pattern evidence of physical contact such as drag marks in blood.
However, precaution should be taken since these reagents are not usually very specific
to blood. Certain substances such as bleach, various metals, and plants may also lead
to chemical reactions with the field tests and the enhancement reagents. In these cases,
the evidence collected is further tested with laboratory examination and analysis.
Recently, portable and field-deployable instruments have been developed that are
capable of processing buccal swabs and potentially other evidence to produce a DNA
profile on-site. It is a fully automated process, using the Rapid DNA technology that
can be completed within 2 h by a trained crime scene investigator or police officer.
These instruments may provide a new tool for expediting the identification of suspects
and developing investigative leads at the scene. Additionally, this technology can
enable law enforcement agents to rapidly determine whether the crimes were isolated
incidents or part of serial crimes committed by the same offender, such as in serial
burglary and arson cases. It can also be used in the identification of human remains in
mass disasters.
6. Documentation
The conditions at a crime scene, including both the individual items of evidence and
the overall scene, must be documented to provide vital information for investigators
and for the courts. The most common documentation methods are drawing sketches
and taking photographs and video-graphs. The sketch is to reflect the positions and the
spatial relationships of items and persons with measurements using a scale. An
investigator usually prepares a rough sketch first and later converts the rough sketch
into a finished sketch.
FORENSIC SCIENCE PAPER No.12: Forensic Biology and Serology
MODULE No.3: Nature and Role of Forensic Biologist in
Crime Scene Investigation
If bloodstains are present at the scene, the location of bloodstain patterns should be
emphasized. Prior to handling and moving evidence, photographs should be taken with
different views: an overall view of the entire scene, a medium-range view showing the
positions and the relationships of items, and a close-up view showing details of the
evidence. Photographs should also include a measuring device such as a scale to
accurately depict the sizes of items such as bloodstains or bite marks.
This can be achieved simply by placing a ruler adjacent to the evidence when it is
photographed. A photograph log sheet can be used to record the chronological order of
crime scene photographs and to note filming conditions and any additional relevant
information. Similar documentation should be prepared for video-graphs when
appropriate. Additionally, written or audio-recorded notes can be used. Notes should
include complete and accurate information of a crime scene investigation, such as the
case identifier number, the identities of the investigators, and a description of the
scene or items (e.g., location, size, and shape). Additionally, any disturbance of
evidence occurring during crime scene processing should be noted.
6. Collection of Biological Evidence
After the crime scene documentation is completed, the collection of evidence can be
initiated. Small or portable items, such as blood stained knives, can be collected and
submitted to a crime laboratory. Large or unmovable items of evidence can be
collected and submitted in sections, such as a section of wall where bloodstains are
located.
Specific care is required for the collection of biological evidence in the following
situations:
Bloodstain pattern evidence: It is especially important to thoroughly
document the bloodstain pattern evidence at a crime scene prior to collection.
Bloodstain patterns can be especially useful in crime scene reconstruction.
FORENSIC SCIENCE PAPER No.12: Forensic Biology and Serology
MODULE No.3: Nature and Role of Forensic Biologist in
Crime Scene Investigation
Multiple analysis of evidence: If multiple analyses are needed for a single
item of evidence, non-destructive analyses should be carried out first. For
example, a bloody fingerprint should be collected for ridge detail analysis prior
to collecting blood for DNA analysis.
Trace evidence: Trace evidence such as hairs and fibers can be present in
blood-stained evidence and should be identified and properly collected.
Control samples: Control (known or blank) samples should be collected from
a control area (e.g., unstained area near a collected stain).
Size of stain: Polymerase chain reaction (PCR)-based forensic DNA
techniques are highly sensitive and allow for the successful analysis of very
small bloodstains. All bloodstains, even if they are barely visible, should be
collected at a crime scene.
Wet evidence: Wet evidence should be air-dried (without heat) prior to
packaging to prevent the degradation of proteins and nucleic acids, which are
used for forensic serological and DNA analysis.
7. Role of Forensic Biologist
Forensic biologists examine blood and other bodily fluids, hair, bones, insects and
plant and animal remains to help identify victims and support criminal investigations.
Using technology in the lab and in the field, forensic biologists collect and analyse
biological evidence found on clothing, weapons and other surfaces to determine the
time and cause of death.
They keep detailed logs and write reports about what they find. Attention to detail is
critical, because a single mistake can cause the evidence to be thrown out of court.
Senior-level forensic biologists may testify in court about their findings.
FORENSIC SCIENCE PAPER No.12: Forensic Biology and Serology
MODULE No.3: Nature and Role of Forensic Biologist in
Crime Scene Investigation
Forensic biologists may become experts in:
• DNA analysis
• Forensic anthropology
• Forensic pathology
• Forensic entomology
• Forensic botany
• Biological chemistry
8. Skills of Forensic Biologist
A forensic biologist must be skilled in applying the principles and techniques of the
physical and natural sciences to the analysis of the many types of evidence that may be
recovered during a criminal investigation. A forensic biologist may also provide expert
court testimony.
An expert witness is an individual whom the court determines possesses knowledge
relevant to the trial that is not expected of the average person.
The expert witness is called on to evaluate evidence based on specialized training and
experience that the court lacks the expertise to do.
The expert will then express an opinion as to the significance of the findings.
Forensic biologists also participate in training law enforcement personnels in the
proper recognition, collection, and preservation of physical evidence.
FORENSIC SCIENCE PAPER No.12: Forensic Biology and Serology
MODULE No.3: Nature and Role of Forensic Biologist in
Crime Scene Investigation
9. Summary
Forensic biology uses scientifically accepted protocols to analyse biological
evidence.
The crime scene investigation process includes maintaining scene security,
preparing documentation, and collecting and preserving physical evidence.
A crime scene investigation begins with the initial response to a scene.
Securing and protecting the scene are important steps in a crime scene
investigation and this task is usually carried out by the first responding officer
arriving on the scene.
If corpus delicti, such as a dead body or a victim’s blood at a crime scene, is
discovered during the investigation, a homicide case can be established and a
suspect can be charged with homicide.
Biological materials such as blood, semen, and saliva emit fluorescent light
under an ALS, which can facilitate the locating of biological materials.
Forensic biologists examine blood and other bodily fluids, hair, bones, insects
and plant and animal remains to help identify victims and support criminal
investigations.
FORENSIC SCIENCE PAPER No.12: Forensic Biology and Serology
MODULE No.3: Nature and Role of Forensic Biologist in
Crime Scene Investigation
