introductory information related to the field of firearms identification; the evidences, the principles involeved in their examination and the categories of guns.
2. CONTENT
1. INTRODUCTION TO BALLISTICS
-forensic ballistics and its applications
- History of forensic ballistics
2. FIREARMS AND ITS BASIC PARTS
-Types of firearms
-Basic parts
3. AMMUNITION
4. PRINCIPLES IN FIREARMS IDENTIFICATION
- Class characteristics
-Individual characteristics
REFERENCES
3. 1. INTRODUCTION TO BALLISTICS
Man has always been fascinated with the use of weapons, including those which propel
any substance of any form towards the desired target.Earliest known projectiles were
arrows, stones or splints that may or may not have been propelled by a bow or a catapult.
This fascination and curiosity gradually lead to the field of ballistics.
Ballistics is a field in mechanics that deals with the study of the launching, flight behaviour
and effects of the projectile on the target. It is also deals with the design in the projectile
and its acceleration in order to achieve the desired performance.
Ballistics is divided into three types:
Internal ballistics- deals with the launching of the projectile, that is, upon ignition or
expansion of compressed air until the projectile reaches the muzzle.
External ballistics- it deals with the flight behaviour of the projectile that is, the effects of
air, wind or any other medium through which the projectile travels after its launching.
Terminal ballistics- it deals with the effects of the projectile upon impact on its
target(including intermediary targets).
4. FORENSIC BALLISTICS
AND ITS APPLICATION
Forensic ballistics is the application of the
principles of ballistics in legal situations so as
to maintain law and order. It includes:
-collection and examination of projectiles of
guns and guns
-toolmark analysis
-study of bullet wounds (here the forensic
pathologist incorporates terminal ballistics
while examining wounds on the corpse).
Forensic ballistic is also known as firearms
identification since it aids in determining the
weapon of offence through examination of the
projectile it supposedly fired.
5. Firearms identification aids investigators in criminal investigation relating to cases like
homicide, assault, robbery, burglary, mob violence and violence related to police
encounters. This field can help us determine:
-whether the crime that took place was accidental, suicidal, negligent or intentional
-the number of shootings during that event and if more than one person was involved.
-the sequence of occurrence of the events.
-the distance between the target and the shooter.
-the type of weapon used in the commission of the crime.
The field of ballistics in criminal investigation has been useful in solving varieties of
many cold blood cases as it also includes tool mark analysis in order to determine the
type of weapon used in the commission of the crime.
Also the condition of the wound can tell a lot about the nature of the weapon used.
6. HISTORY OF FORENSIC BALLISTICS
1493-1508- Emperor Maximilian of Germany proposed rifling of
guns in order to impart rotatory motion to the projectile during
firing. However the fact that rifling marks on the projectile could
aid in identification of the weapon that fired it was not
recognized until the 19th century.
1835- Henry Goddard of the Bow Street Runners examined the
bullet from the crime scene and noticed a defect on it. On
comparing the mold found in the suspect's home to the defect
on the bullet a positive comparison was made which lead to the
conviction of the suspect. Bullets those day were made by
pouring lead into a mold.
1860- In the Regina vs. Richardson case the evidence included a
newspaper wadding used to seal the bullet from the gunpowder.
The wadding was found on the victims wounds which contained
The London Times paper of March 27th 1854. The same material
of the same paper was found in the suspect's home. The
comparison of these two samples lead to conviction of the
suspect.
7. 1902- Oliver Wendell Holmes turned to magnification on account of
increased firearms manufacture which lead to standardization of
rifling.
1912- Professor Balthazar used photography to document
circumferences of the bullets found at the crime scenes and those
test fired.
1925- Charles E. Waite along with Calvin Goddard, Philippe Gravelle
and John Fischer founded the Bureau Forensic Ballistics in New York.
Gravelle developed comparison microscope and Fischer invented the
helixometer.
Calvin Goddard became known for his identification work in the
Sacco and Vanzetti case.
Fig: Calvin Goddard examining the barrel of
a revolver using a helixometer.
8. 2. FIREARMS
A firearm is a mechanical device adapted to hurl a
projectile into air or any other medium by the action of
explosive forces or any other forms of energy.
The earliest known firearm was a firelance used by the
Chinese during the 10th century A.D.(in the figure, a
Chinese firelance used to fire either an arrow or a group
of solid projectiles).
According to the Indian Arms Act 1959, a firearm is a
device of any description that is adapted to hurl
projectile or a group of projectiles of any form or design
by the action of explosions or any other form of energy.
The first drawing of the most primitive form of the gun
was made in the 14th century.
9. BASIC PARTS OF A FIREARM
Gun is a type of modern firearm made out of predominantly
steel. The basic parts of a gun are:
Stock
Action
Barrel
Stock is the part that holds other parts of the firearm on
place and is even used as support by the shooter during
firing. It is also a safety feature while handling guns. In
semiautomatic and automatic guns it is called as a magazine.
Action is the mechanism for loading, unloading, ejecting and
extracting the ammunition.
Barrel is a metallic tube through which the projectile travels
upon firing and it provides space for the expansion of gases. It
may be rifled or smooth on its inner surface.
10. CLASSIFICATION OF FIREARMS
Studying the classification of firearms is useful especially when it come to determining the type
of gun used in the commission of the crime.
Firearms are classified into:
Single shot- in these type of firearms the gun has to be loaded every single time after every
shot. Many shotguns come under this category.
Repeaters- in this type of firearm, manual loading or sometime extraction of the ammunition
has to be done after each shooting takes place. Examples are revolvers and some rifles.
Semi automatic- in this type automatic extraction and ejection of the spent cartridges and
loading of live cartridges take place after each shooting as long as the trigger is pulled. For the
next shooting the trigger is released and again pulled to repeat the entire process.
Automatic- this type is similar to semi automatic guns except that as long as the trigger is
pulled automatic loading, extraction and ejection of the cartridges occurs repeatedly provided
that the magazine is not exhausted. Examples include machine submachine guns.
12. A SUB MACHINE GUN( AUTOMATIC) A SINGLE SHOT PISTOL(BREECH LOADING)
13. The firearms can also be classified based on the positions of where the ammunition is loaded. They
are:
Breech loaders
Muzzleloaders
Magazine loaders
Also rifles are classified into:
Pump action
Bolt action
Break action
Lever action
Automatic
Rifles are firearms with a long barrel length with a rifled bore.
Firearms are also classified into:
Handguns- example: revolvers, self loading pistols
Shoulder guns- example: rifles
Improvised firearms are those guns which do not resemble a typical gn but are made from the
available materials(in fig).
14. Classification of firearms based on their inner barrel surface or bore
RIFLED BORE
.These are characterized by the presence of
furrow portions that alternate each other.
These depressions or furrow like portions are
known as grooves and the raised portions
between them are called lands. They are
arranged in a spiral manner.
. The motion of the projectile that travels
through the bore and then
.in these type of firearms, bullets are used.
. The measurement for the bore is
caliber(distance between two diagonally
parallel grooves).
.Absence of choke
SMOOTH BORE
These are characterized by the absence of
lands or grooves. The cross section of the
bore is circular at any point.
The projectiles travel in a forward motion
and the range is very much less.
. In these type of firearms pellets, slugs or
shots are used.
.the measurement for the bore used is
gauge or bore diameter.
.presence of choke
16. 3. AMMUNITION
Ammunition means anything that contains a projectile and a propellant. In a
broad sense it can mean materials used for combat or war and these include
grenades, missiles, riot pistols, explosives etc.
Its short form is ammo. It is derived from the French word 'la munition which
means material used for war.
A single unit of ammunition for a gun is equivalent to a single live cartridge.
A cartridge is a metallic enclosure consisting of the projectile, primer and the
propellant.
It is made up of metal or plastic.
17. Components of a cartridge
A cartridge has basically four components:
Primer- it is a friction or impact sensitive material primarily
made up of a fulminate of mercury.
Propellant- it is of two types; gunpowder or smokeless
powder. Gunpowder is a primitive type of propellant. It
produces a lot of residues upon firing and this can corrode
the quality of the gun.it is made up sulphur, charcoal and
potassium nitrate in the ratio 10:5:85.
Smokeless powders are made out of nitrocellulose and
nitroglycerin.
(in fig. A rifled cartridge with a flat nosed bullet)
.
18. Projectile- it is located on the anterior end of the cartridge.it can be pellets, slug or shot(in case of
smooth bore guns) or a bullet in case of rifled guns.
Cartridge case- they are used to hold the
components in place. They have been made up of
steel, aluminum, copper and brass. Brass is the
most durable.
Wads- these are either made up of plastic or
cardboard. They are found in shotgun cartridges
where they ensure separation between the
pellets and the powder.
20. 4. PRINCIPLES IN FIREARMS IDENTIFICATION
The principle that no two firearms even of the same make and model made one after
can impart identical marks onto the bullet being fired from it is similar to the
thumbprint we apply for fingerprints.
When a bullet is fired from the gun, marks get imprinted not only on the bullet but
also onto the cartridge case. These marks are produced by the parts of the firearm. They
are:
Firing pin- the marks produced by the firing pin onto the cartridge case are very
significant in identification of the suspected weapon.
Breech face- the area surrounding the firing pin hole is the breech face. During firing
when the cartridge case is pushed onto the breech face where the marks get imprinted
onto the backside of the cartridge case.
21. Chamber- the area where the ammunition is inserted(in case of breech loading firearms).
Usually this part is insignificant in context to identification since the diameter of the chamber is
greater than those of the bullet and the cartridge case separately.
Extractor and ejector- these parts of the firearm
come in contact with the cartridge cases.
Leed- It provides slippage marks onto the bullet
when the bullet travels form the chamber to the
barrel during firing.
In fig- firing pin indentations on the base of a
rifled cartridge observed through microscopy.
22. Class characteristics include the bore diameter of the firearm, the angle of twist of the lands and
grooves, the direction of twist of the lands and grooves and the width of the grooves and lands.
These characteristics help us to narrow down to guns of the same make and model.
Individual characteristics are the finer
imperfections of the indentations produced by
the firearm. These help us find the specific
firearm. These imperfections are due to
manufacturing, use of the weapon and
corrosion of the weapon.
in fig. Striations produced on the cartridge case
due to chamber.
23. Marks on the test cartridge(left)
compared with those of the questioned
cartridge using a comparison microscope
of 20x.
24. References
Heard, B. (2008): Handbook of firearms and ballistics, Examining and
interpreting forensic evidence( 2nd edition, Wiley) ,416 pages.
Rao.M.S., Maithil.B.P., Kumar.S(2009): Crime Scene Management, A Forensic
Approach(1st edition, Selective and scientific books), 439 pages.1st edition.
Maithil.B.P. (2012): Physical evidence in crime scene investigation, The silent
witness(5th edition, Selective and scientific books), 432 pages.
