CHAPTER 10

Firearms Identification
Introduction
Identification is one of the principal objectives of crime investigation, to establish the
identity and location of the suspect. The prober is aided by different forensic sciences. Pieces of
physical evidence are always left in the crime scene that will provide valuable clues or
information. Studies have shown that no twe firearms, even those of the same make and model,
will produce the same unique marks on fired bullets and cartridge cases.
Manufacturing processes, use and abuse leave surface characteristics within the firearm
that cannot be exactly reproduced in other firearms. Firearms do not normally change much over
time. This allows for firearms recovered months or even years after a shooting to be identified as
having fired a specific bullet or cartridge case.
Tests have been conducted that found that even after firing several hundred rounds
through a firearm the last bullet fired could still be identified to the first. It should be noted that
not all firearms leave consistently reproducible marks. Bull rearms produce nonmechanical
fingerprint" on the bullets and cartridge cases that pass through them.
Firearms Identification
It is a discipline of forensic science which primary concern is to determine whether or not
the submitted Collected fired cartridge cases, fired bullets or other ammunition components were
fired from a particular firearm.
This science is often referred to as "FORENSIC BALLISTICS". It is regarded as the
highest form of an uncontestable and conclusive piece of evidence with an outmost legal
significance.
In the investigation of crimes involving firearms and ammunition, the police authorities
are basically guided by this science. Today, firearms examiner is well-demanded and looked for
to assist the law enforcers in the solution of the criminal cases involving firearms. The science of
firearms identification has long been recognized and accepted as a potent aid in the civil and
military court many decided criminal cases, both on dispensing justice as proven in
One famous and controlling decided criminal case by the Supreme Court, recognizing the
testimony of a Forensic Firearm Expert was the case of the PP vs Timbol Bros et al. The case
fully established the relevance of this branch in police science in criminal identification and
investigation
Significance of Firearm Identification
The significance of firearms identification in crime detection and investigation is obvious
and should not be overemphasized. History shows uh and swiedge in this area of forensic science
greatly helps in facilitating the investigation of criminal cases. 10. Ejector port mark these are
marks caused by the contact between the cartridge case and the ejector port of the firearm.
Principles Involved in Shell Identification
1. The breechface and the firing pin of every firearm have microscopic individualities of their
own.
2. Every firearm leaves its fingerprint or thumb mark on every cartridge it fires.
3. The whole principle of identification of shells is predicated or based on the fact that since the
breech face of every weapon must be individually distinct, the cartridge cases which fires, are
imprinted with this individuality. The imprints of all cartridge cases fired from the same weapon
are similar, and those on cartridge cases fired from different weapons are different.
FIREARM CHARACTERISTICS RELATED TO IDENTIFICATION
1. Class Characteristics
These are characteristics that are determinable even prior to the manufacture of firearm's. They
are factory specifications and within the control of man. they serve as the basis for identifying a
certain group y class of firearms. These are:
1.Bore diameter/ caliber the diameter in which the bore was reamed. It is the distance measured
between two opposite lands inside the bore.
Different system of measurement of the caliber of firearm
a. American System - expressed in hundred on an inch. Ex. .38 special
b. English System - expressed in thousands of an inch. Ex. .357 magnum
c. Continental/European - expressed in millimeter. Ex. 9 mm
2. Number of lands and grooves - the number of lands is always equal with the number of
grooves.
3. Width of lands - it is dependent on the bore diameter, the bigger the caliber, the wider the
width of the lands and grooves. It is the remainder of the circumference after subtracting the
groove width.
4. Width of grooves - it 15 measured as the shortest distance between the two sides or edges of
grooves.
5. Direction of twist it is the twisting of the lands and grooves whether clockwise or
counterclockwise, for the bullet to have gyroscopic motion during its fight.
6. Depth of groove measured on the radius of the here as seen in the cross section. It is equal to
the height of the side of the lands.
7. Pitch of riflings - the twist of lands and grooves. It also refers to the distance advanced by the
riflings in a complete run.
General Type of Riflings
1. Steyr Type - 4RGL (four lands and grooves, the direction of twist is to the right and the width
of grooves is equal to the width of lands)
2. Carbine Type - 4RG2X (four lands and grooves, the direction of twist is to the right and the
width of grooves is twice to the width of lands)
3. Smith and Wesson Type - 5RGL (five lands and grooves, the direction of twist is to the right
and the width of grooves is equal to the width of lands)
4. Browning Type - 6RG2X (six lands and grooves, the direction of twist is to the right and the
width of grooves is twice the width of lands)
5. Colt Type - 6LG2X (six lands and grooves, the direction of twist is to the left and the width of
grooves is twice the width of lands
6. Webley Type - 7RG3X (seven lands and grooves, the direction of twist is to the right and the
width of grooves is thrice the width of lands)
7. Army type or 4RG 3X (four lands and grooves is thrice the width of lands)
8. Winchester Type - 6RG3X (six lands and grooves, the direction of twist is to the right and
the width of grooves is thrice the width of lands)

II. Individual Characteristics

These are characteristics peculiar and not found in all other firearms. They serve as the
basis for the identification of a particular firearm and identifiable only after the manufacture of
the firearm. These characteristics are beyond the control of the man and have random
distribution beside the gun. Their existence made firearm is brought about by the tools used
manufacture in their normal operation resulting in tear, abuses, mutilations, corrosions, erosions
and other fortuitus causes. These characteristics are generally found in the interior surface of the
gun barrel and breech face.

9 Problems of Firearm Identification

1. Given a bullet; to determine the caliber and type of firearms used.
2. Given a cartridge case; to determine the caliber, name of the manufacturer and the type
of firearm used.
3. Given a bullet and firearm, to determine whether or not the bullet was fired from
suspected firearm submitted.
4. Given a fired cartridge cases and suspected firearm, to determine whether or not the
cartridge case was fired from the suspected firearms submitted.
 5. Given two or more bullets, to determine whether or not the bullets were fired from
only one weapon.
6. Given two or more fired cartridge cases, to determine whether or not the cartridge cases
were fired from only one weapon.
7. Given a firearms, to determine whether it is serviceable or not.

8. To determine whether or not the ammunition is serviceable.

9. To determine the shot sizes of the pellet or shots.

Fired Bullet Identification

a) A submitted firearm will be fired in the bullet recovery box several times to obtain
standards from the firearm.

b) Fired standards are examined first to determine if in fact the barrel is producing striated
marks in a unique and consistent pattern.

c) The comparison macroscope consist of two macroscopes mounted side by side and
connected by an optical bridge. There are two stages on the lower part of the macroscope
that the bullets to be compared are mounted on.

d) The stages that the bullets are attached to allow the bullets being examined to be rotated
on their axis and moved up, down, to the left, and to the right.

Result of Bullet Identification

When comparisons are made between firearms and fired ammunition, the results can read as
follow:
a. Exhibit 1 (bullet) was identified as having been fired from Exhibit 2 (firearm).
This conclusion is reached after all class characteristics agree and a sufficient
correlation between individual characteristics is found.
b. Exhibit 1 (bullet) could neither be identified nor eliminated as having been fired
from Exhibit 2 (firearm). All comparisons were inconclusive. This conclusion is
reached if class characteristics agree but there is an insufficient correlation
between individual characteristics.
c. Exhibit 1 (bullet) was not fired from Exhibit 2. This conclusion is reached if class
characteristics agree.
Principle in Firearm Identification
1. It is refined tool marks identification.
2. The natural wear and tear of the tools are involved.
3. When the soft surface comes in contact with the s no hard surface, it leaves with the
impressions or scratches from any irregularities on the hard surface.
4. The principle of individuality that is no two things is absolutely identical.

BULLET IDENTIFICATION
Bullets collected for comparison to a specific firearm are examined first to see if they are
of a caliber that could have been fired from the submitted firearm. They are then examined to
determine if the pattern of rifling impressions found on the bullet match the pattern of riming
contained in the barrel of the questioned firearm. If these class characteristics agree the next Step
is to try to make a positive match between the individual characteristics that may have
transferred to the bullet from the barrel. Imperfections in the surface of the interior of the barrel
leave striations on the projectiles. Striations have the potential to be consistently reproduced in a
unique Pattern on every bullet that passes down the barrel of a firearm.
Marks Found on Fired Bullets
a. Lands marks - depressed portion caused by lands that can be found in the fired bullet.
cylindrical surface of the
b. Groove marks raised or elevated portions caused by the grooves that can be found in the
cylindrical surface of the fired bullet.
c. Skid marks - found on the anterior portion of the fired bullets and caused by the forward
movement of a bullet from the chamber before it initially rotates due to the rifling inside the
barrel.
d. Stripping marks/ slippage marks - found on a bullet fired though loose fit barrels wherein
the riflings are already worn out. Shaving marks found on bullets fired from a revolver due to
poor alignment of the cylinder with the bore.

Principles Involved in Bullet Identification

1. No two barrels are microscopically identical as to the internal surfaces is the hangs or their
Sees.
2. When the bullet is fired from a rifled barrel, it becomes engraved by the riflings and these
engravings will vary in its minute details with every individual firearm. Therefore, the
engravings on the bullet fired from one barrel will be different from another bullet fired from
another barrel. On the other hand, the engravings on bullets fired from the same barrel will be
the same.
3. Every barrel leaves its thumb mark or fingerprint on every bullet in it.

Marks Found on Fired Shells

General Types of Marks in Fired Shells
a. Striated Action Marks are common to cartridge cases that have passed through the action of
an auto loading or repeating firearm. Striated action marks can be produced on cartridge cases by
contact with a number of different areas within the firearm.
b. Impressed Action Marks, with a few exceptions, are produced when a cartridge case is fired
in a firearm. The two most common impressed action marks are firing pin impressions and
breechface marks.
1. Chamber mark - found in the body of the shell due to the irregular makings in the chamber.
It is a result of any or all the following
a. Chambering
b. Expanding during firing
c. Extraction

2. Firing pin mark found in the primer cup or the rim of the cartridge case caused when the
primer cup struck by the firing pin.
3. Firing pin drag marks - produced when a projecting firing pin comes into contact with a
cartridge case or shotshell during the extraction, ejection cycle.
4. Shearing marks -firing pin mark found near the firing pin mark and usually found in pistols.
5. Extractor mark extracting groove in automatic firearms produced when cartridge case comes
in contact with the extractor rod of a firearm in the withdrawal of an empty cartridge case after
firing.
6. Ejector marks located in the rim in automatic firearms produced when A cartridge case
comes in contact with the ejector of a firearm after firing.
7. Pivotal mark - found on the shell caused by turning of the cartridge.
8. Magazine lip markings - found at the low points of the rim of the base of the shell; caused by
the magazine lips during the loading of the eartridge into the magazine for firing.
9. Breech face marks - found on the base of the cartridge case as a result of the rearward
movement of cartridge case during firing. In this problem, marks found on the head stamp must
be obtained to identify the manufacturer, the year of manufacture and the possible firearm that
used such type of cartridge The specimen must be described and take note of the place of its
recovery (Physical Examination).
Cartridge Case Identification
 Like bullets, cartridge cases can be identified as having been fired by a specific firearm.
As soon as cartridges are loaded into a firearm the potential for the transfer of unique tool marks
exists. However, the cartridge does not have to be fired for these marks to be transferred. Simply
loading a cartridge into a firearm identified can cause unique identifiable marks that can be later.
Results of Cartridge Case Identification
a. Exhibit 1 (cartridge case) was identified as having been fired by Exhibit 2
(firearm). This conclusion reached if the action marks present on the questioned
cartridge case are determined to be because of the actual firing process.
b. Exhibit 1 (cartridge case) could neither be identified nor eliminated as having
been fired by Exhibit 2 (firearm). This conclusion reached if the cartridge case
lacks sufficient action marks to be identified as having been fired by the
questioned firearm or the firearm in question fails to produce reproducible
individual characteristics on standard. All general class characteristics
such as caliber and firing pin shape would have to agree.

c. c. Exhibit1 (cartridge case) was identified as having passed through the action of
Exhibit 2 (firearm). This conclusion can be reached if the cartridge case is found
to have action marks that result from simply loading and / or unloading a cartridge
case in a firearm.
Purpose of Three Standards
1. First is for preliminary
2. Second is for confirmation
3. The third is for the conclusion

Related laboratory examinations

1. Gunpowder residue Analysis – It is principally composed of burned and unburned parties
from explosive primer, the propellant, as well as components from the bullet, the cartridge case
and the firearm used.
2. Serology examination and autopsy – conducted by the Medico Legal Officer.
3. Developing of latent fingerprints – from the de avered ballistic exhibits through gas method
or using a funning box.
4. Macro etching examination – to verify altered firearms serial numbers by the Physical
Examination Division.

Thank you!