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Embed code for: Ballistics
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Meaning, Purpose & Scope:
Ballistics is the study of projectiles in motion. The term ballistics is derived from the Latin word “ballista” which refers to a crossbow like device for throwing stones by means of twisted ropes.
Forensic Ballistics is the examination and identification of firearms, cartridges, fired cartridge cases, bullets, gun powder, wads, pellets, etc. Further ballistics section links the firearm with fired cartridge cases and bullets, determine the range of fire & angle of firing etc
In legal context it deals with the guns, revolvers, pistols, missiles, etc and the bullets, pellets and other fast moving objects hitting the targets that proves the period using the firearm etc…….
Physical evidence pertaining to Ballistics may be available in Murder, assault, suicide, attempt to murder, dacoity and in many other cases.
TYPES OF EXHIBIT REFERRED FOR EXAMINATION
The manual covers the following types of exhibit referred to Ballistics Laboratory for forensic analysis.
Firearms, ammunition and parts thereof
Victim’s/ accused’s apparel
Swabbing or lifting from body parts of suspect shooter/victim
Parts of skin, bones, hair and other body parts affected by shooting
Inanimate object(s) affected by shooting
Unburnt/partially burnt powder charge
Equipments required for examination
Comparison microscope with photomicrographic attachment and accessories.
Vernier Calipers, screw Gauge, Magnifying glass, Measuring tape
Velocity Measurement System
Ballistics can be broadly divided into three parts:
External Ballistics and
Internal Ballistics: Internal Ballistics deals with the motion of projectiles from the time the trigger mechanism is activated till it leaves the muzzle end of the barrel. The rate and manner of burning of the propellant, the nature of development of gas pressure on the gun, barrel and breech, etc., are studied under this read.
External Ballistics: External Ballistics deals with the motion of projectiles during the rest of its trajectory through the air. The stability of the projectile during the flight, wind deflection, gravitational pull, etc., can be studied under this branch.
Terminal Ballistics: Terminal Ballistics deals with the impact of projectiles upon the target. It includes the study of wound ballistics.
Firearm: A firearm is a device which can set off projectiles to a considerable distance with high velocity. The force to propel these projectiles comes from the propellant. When the propellant burns it builds up gaseous pressure which propels the projectiles out of the barrel of the weapon. A firearm is so called because a flame is generated, and it is this flame which is responsible for propelling the projectiles.
Classifications of Firearms:
The modern firearms are classified on the basis of several characteristics.
Handling Characteristics – Handguns, shoulder arms.
Bore Characteristics – Smooth bore and rifled bore firearms.
Loading Characteristics – Muzzle loading, breech loading, or magazine loading firearms.
Action Characteristics – Lever-action, bolt-action, self-loaders, automatics.
Firing Characteristics – Single shot, repeaters.
Use – Sporting firearms, service firearms.
Shotgun is an important firearm, which falls in the category of shoulder arms. All shotguns are smooth bore firearms, that is, the cross section of the barrel at any point makes a perfect circle. They are known as shot guns because they fire a single ball, slug or a charge consisting of a considerable number of lead pellets (shots). A shotgun may be single or double barreled. The barrels may be joined side by side or they may be one over the other. The double-barreled guns are either ‘hammer’ or ‘hammerless’ types, the latter being the more modern type. In hammer guns the hammers are cocked with the hand. In hammerless the hammer action is enclosed in the body of the gun and the hammers get cocked automatically when the breech is opened and closed. The shotguns barrels have varied bore diameters and are designated by a number and gauge or bore. Thus, in a 12-bore shotgun, the internal diameter of the barrel is equal to the diameter of a spherical lead ball made of pure lead and twelve such lead balls, which correspond to the diameter of the barrel together weigh a pound. A 12 bore shot gun will have 0.729 inches bore diameter. There are 10 gauge, 16 gauge, 20 gauge, and 28 gauge shot guns. Only exception is that when the diameter of a smooth bore barrel is less than 0.5 of an inch i.e., smaller than 32 gauge, the bore is designated in decimals of an inch e.g., 0.410 inch musket. Shotgun barrels are often narrowed down to reduce the diameter of the barrel near the muzzle, to control the dispersal of the shot charge and thus increase the effective range. This constriction is known as choke and varies from 1 to 0.25 mm. The two ends of the barrel of a shotgun are called the breech and the muzzle end. Breech end is also known as chamber end. The breech end of the barrel has a special cavity to house a cartridge. The chamber end carries extraction and ejection mechanisms. When the cartridge is loaded from the breech end it is known as breech loading firearm. All modern firearms, whether rifled or smooth bore are breech-loading weapons.
Shotguns of muzzle loading type are also known. In this the cartridge components are loose and inserted from the muzzle end. A percussion cap, placed on the nipple, when struck by the external hammer sets the projectiles in motion in case of muzzle loaders.
Bore: “Bore” is the term associated with smooth bore fire arms. It is a number indicating the size of the internal diameter of the barrel, and represents the number of spherical balls of pure lead each exactly fitting the inside of the bore which together make up a pound. For example, the internal diameter of a 12 bore shotgun is equal to the diameter of a spherical ball of pure 1/12 pound of lead. The internal diameter of the 12 bore gun barrel is 0.729 inches.
All rifled arms fire a single bullet. They have a much longer barrel and can fire high-powered ammunition. Rifles are characterized by their calibers. The caliber is the actual measure of the bore diameter of the barrel between two opposite lands.
The caliber is measured in decimals of an inch e.g., 0.303”, 0.22”, 0.38” etc., or in millimeters, e.g., 7.65 mm, 9 mm etc.
The rifled barrels are grooved. The grooves are cut in the form of spirals from inside the bore. The raised parts between these are known as lands. The number of grooves in a rifle varies. The width of the grooves in the barrel is cut in various ways. The spiral groove is obtained by gradually and uniformly turning the cutter, while cutting the groove. This turning is called the twist and the angle of the turning is called the pitch. The rifling in the barrel gives gyratory motion (spinning) to the projectile, which continues even in flight. The gyratory motion maintains the bullet in stable nose-on flight, which reduces the air resistance and enhances the degree of accuracy.
Rifles are of different actions. Most common are bolt action and semi-automatic action. In bolt action loading and unloading operations are carried out through a bolt with a knob. The firing pin assembly remains inside the bolt. The bolt head is fitted with an extractor, 0.303, 0.22 are examples of rifles.
Hand guns: These firearms have short barrels and grips. These can be operated with one hand.
Pistols:- These are hand arms having short barrels which are usually not more than 10 inches long. Pistols have a magazine, which is enclosed in its grip and it can be held and fired with one hand. Pistols are normally semi-automatic or self-loader type, in which by the pull of trigger a cartridge is fired. Its effective range is 100 yards and muzzle velocity is 1200 ft/sec. E.g., 9 mm, 7.65 mm pistols.
Revolvers:- The revolver has a revolving cylinder arranged behind the breech end of the barrel, which can accommodate 4 to 7 cartridges. The size of the revolvers also vary e.g., 0.32”, 0.38”, 0.45”. For every trigger operation, the mechanism rotates the cylinder in such a way that the next chamber becomes aligned with the barrel of the revolver. The barrel length is about 7 inches and effective range is about 100 yards. In the single-action revolver, the hammer must be cocked by hand after each shot and the weapon is then fired in the usual way by pressing the trigger. In the double action type of revolver, the hammer can be cocked by hand, but it can also be cocked and fired by a prolonged pull of the trigger.
The differences between pistols and revolvers can be summarized as follows
Pistols Revolvers Magazine is arranged in the grip.
The magazine accommodates more than eight cartridges.
The trigger pull is less.
The weapon is light in weight.
A misfired cartridge cannot be easily remove A cylindrical magazine is arranged behind the breech end of the barrel.
Normally the cylinder accommodates less than eight cartridges.
The trigger pull is more.
It is somewhat heavy (due to its cylinder)
A misfired cartridge can easily be removed.
There are other types of firearms which do not fall into the above classification pattern. Country-made firearms or improvised firearms fall into this category. Other types are toy firearms, freak firearms, etc.
Improvised firearm or country made firearms: These are home made firearms usually manufactured by blacksmiths using water pipes and standard ammunition is used. Each of these firearms is unique in its mechanism and mostly smooth barreled.
The standard ammunition is made of the following basic components:
Primer and primer cap.
Powder or propellant.
It provides housing for various components of cartridge. It is usually made of brass for rifle, pistol and revolver. For shotgun it is made of card board\ the base of which is made of brass. Plastic cartridges are also manufactured.
Metallic cartridges have the following components:
Metallic cartridge case or shell
Percussion cap or primer
Propellant or gun powder
SCHMATIC DIAGRAM SHOWING THE COMPONENTS OF A METALLIC CARTRIDGE
Shot gun cartridges have the following components:
paper cartridge case or shell
propellant or gun powder
spherical balls or lead pellets (shot)
over shot wad, under shot wad, air cushion wad and over powder wad
FIGURE SHOWING THE COMPONENTS OF 12 BORE CARTRIDGE
The base of the cartridge case may be rimmed or rimless. Rimmed cartridge helps in positioning the cartridge correctly in the chamber and facilitates extraction. The rimless cartridges are used in pistols and other automatic and semi-automatic firearms. A cartridge case may be rim-fire or center-fire type. In the rim-fire cartridge, no separate primer cap is provided. The primer composition is located in the rim itself. Whereas, in the center-fire cartridge, the percussion cap containing the primer mixture is situated in the center of the base of the cartridge case.
This contains mercuric fulminate or lead azide, which is a very sensitive chemical mixture and when the firing pin strikes on it, it gives rise to a hot flame.
The powder charge gets ignited through primer and converts into gas at a very rapid rate. The generated gas, under compression, develops pressure in the cartridge and finally forces out of the barrel propelling the projectile. Three types of propellant charges are known:
Gun powder (black powder): This consists of potassium nitrate, charcoal and sulphur the ratio of 75:15:10.
Smokeless gun powder: The basic components of these powders are Nitroglycerine and Nitrocellulose (gun cotton).
Semi-smokeless powder: It is a mixture of Nitrocellulose and black powder in the ratio of 20:80.
Wads are essential components of shot gun cartridge. Wads are used in the cartridge primarily to keep the propellant and shot charge in their respective positions. In addition they seal the barrel to prevent escape of gases and, consequently, their respective reduction in velocity. In shotgun cartridges, a number of wads are used viz., over powder wad, cushion wad, undershot wad and overshot wad.
In shotgun cartridges the projectiles consists of small lead balls or pellets. These pellets are of different size, denoted by numbers and the larger pellets by letters e.g. number 1 and 4 contain 100 and 170 pellets respectively; LG and SG contain 6 and 8 pellets respectively.
In rifles, revolvers and pistols the projectile consists of a single bullet, which fits the bore size. Bullets are made of lead, alloyed with tin or antimony. High velocity bullets have a jacket made of copper, cupro-nickel alloy or steel. Core of such bullets is composed of lead alloy. The bullets are made in various shapes and forms. They may be streamlined, boat tailed or with a flat base. The nose may be flat, round or pencil nose, the size may be short, medium or long.
Mechanism of Firing:
When the trigger of a firearm is pressed, it releases the hammer or the striker with considerable force. The striker compresses a pressure sensitive material contained in the percussion cap. This generates a hot piercing flame, which ignites the propellant charge. The charge quickly transforms into gas. Due to limited space in the cartridge, the large volume of gas so produced develops a very high pressure. The pressure so developed forces out the bullet or the shot charge through the barrel towards the target.
While the bullet moves forward the cartridge case is pushed backward. The case, therefore, comes in contact with the firing pin and the breech face of the breechblock, and picks up marks from their surface.
The cartridge which also expands all round due to the tremendous pressure developed in it comes in intimate contact with the chamber and sometimes may carry chamber marks. The fired cartridge case is extracted out of the chamber by an extractor and then ejected out of the gun by an ejector. In the process both extractor and ejector are likely to leave marks on the cartridge case.
All these marks are very useful which can afford identity of the bullet or the cartridge case with the concerned firearm.
Identification of Firearms:
In order to link the weapons recovered from the suspect, it has to be established that from the crime weapon the cartridge cases and bullets recovered at the crime scene were fired / discharged. The crime weapon will be test fired loading it with the cartridge of the same make by firing into a bullet recovery box filled with cotton to obtain bullet bearing marks characteristic of the barrel. The test cartridge case and test bullet are thus obtained.
The following aspects are to be noted before one can arrive at an identification of a firearm
Whenever a hard object acts on a soft object, the hard object leaves its own individual characteristics on the soft object.
All objects acquire some peculiar characteristics due to usage, wear and tear, maintenance and user’s peculiarities and so on. No two firearms will leave identical individual characteristics on the cartridge cases.
Therefore the bullets fired and discharged from firearms invariably possess the characteristics marks of the firearms used to fire the ammunition.
The crime cartridge case and test cartridge case are examined and compared under comparison microscope and the following marks are examined.
Breech Face Marks: At the moment of the firing the base of cartridge case strikes with a tremendous force on the breech block there by the impressions on the breech block will be registered on the base of the cartridge case. These breech face marks in test and crime cartridge cases are compared.
Firing Pin Impressions: Because the firing pin strikes the primer cap with force, there will be marks of firing pin on its surface. These firing pin marks are different for different firearms and are rarely or never duplicated.
Extractor and Ejector Marks: Most of the firearms possess extractor or ejector or extractor cum ejector. These impress on the rim of the cartridge case in definite and recognizable marks like size, shape and location.
Chamber Marks: At the time of firing, the cartridge case expands and may take up marks or certain irregularities of the chamber.
Bullets fired through rifled firearms receive both the class as well as individual characteristics of the barrel from which they are fired. The bullet will show not only the primary markings left by the lands and grooves of the rifled barrel but will also reveal the fine striations in all the marks. These are the imprint of the small irregularities in the barrel, and are never duplicated by different weapons. To determine whether or not a particular firearm has fired the questioned bullet, a detailed comparison is made of markings on the question bullet with corresponding markings on the test bullets fired through the suspected weapon. A comparison microscope is used for this determination.
Direction of Fire:
The direction of fire can be of great help in the reconstruction of the events in the firearm offences. It may help to find out whether the incident is suicidal or accidental firing. The direction of fire can be ascertained by the shape and nature of entry wound. The systematic study of the bullet hole at the point of entry, its path and the point of its location in the body or the exit wound may help establish the direction of fire.
Range of Fire:
Range is the distance between the muzzle end of the barrel and target and can be estimated by studying the following:
Close Range Firing Effects:
a. Burning / Scorching: When a projectile leaves the fire arm, the gases also come out at very high temperatures. When the gases combine with oxygen of the atmosphere a flame is produced which extends up to a few inches. If the weapon is close to the target, this flame produces burning or scorching or charring of the target. Burning may occur up to a distance of 6” in case of service rifle or 12-bore shot gun, whereas in hand guns it is up to 2 to 3” only.
b. Blackening: the propellant gases consisting of carbon particles are deposited around the wound and produce blackening. This blackening can be easily wiped off because it is merely the deposition of carbon particles around the wound. However, the blackening due to burning cannot be wiped out. In case of service rifles or shot guns blackening may occur up to a distance of 12”, and up to 6” in case of hand guns.
C. Tattooing: Deposition of un-burnt and partially burnt propellant around the projectile hole is called tattooing. If the entry wound is not covered by clothes, these particles may produce contusion. In case of service rifles or shot guns tattooing may be observed up to a distance of 4 feet. In case of hand guns it is up to one foot. Beyond this range it is not possible to estimate the range in case of rifled fire arms. But it is possible to estimate the range up to 2 meters in case of 12 bore shot guns with 12 bore KF special cartridges. The shot charge discharged from 12 bore shot guns makes a single hole, up to a distance of (range) 2 meters.
2 meters Diameter of the Single hole
At a distance of two meters the individual pellets start separating from the main charge. This is called cookie cutter etching. At 2 to 5 meters distance a rat hole is formed, i.e., a central hole surrounded by several holes caused by the penetration of the individual pellets. The diameter of the central hole varies from about 2 to 6 cms.
Shot Patterns: - At close ranges, the shots emerging from the barrel travel with considerable force in a closely held group. The wads also get associated with the shot group up to a few meters from the muzzle. The wads soon begin to loose their velocity and get dropped. The shots progressively separate and spread out. As the range increases, the shots may spread to cover a wider area but will have little force. Because of this progressive change in the shot and wadding pattern, it is possible to determine with considerable accuracy the distance of firing. The pattern, however, must be available for study and the concerned weapon and ammunition must be obtained for test firing. The same gun and the same kind of ammunition are used to test fire at different measured ranges to match with the pattern revealed in firearm offence under investigation.
Wad Distribution: - A number of wads are found in shotgun ammunition. They are propelled along with the other charge. They may enter the target up to about three meters. If they do not come across any obstruction they can travel up to the five meters. If the distance between the victim and the wads is known, the range of fire may be determined.
Muzzle Pattern: - When a firearm is fired in contact with the target, an imprint of the muzzle is left on the target. In such wounds the whole charge will enter into the target. No burning, blackening and tattooing are observed around the entrance hole. Often the entrance hole will bear a tear on the cloth or skin in the form of a cross.
Detection of GSR on Hand:
When a firearm is fired, especially a revolver, Gun Shot Residue (GSR) from the propellant and the primer may be blown through the cylinder. Traces of such residues are sometimes transferred on the hands of the shooter. Detection of such residues helps the investigator in identifying the fire.
A variety of methods have been in practice for sometime. Walker devised a test known as “Walker test”. It was developed to detect nitrite in the residue using desensitized photo bromide paper. Another spot test called “Paraffin test” was also developed to detect dermal nitrate on the hand of the firer.
The hand washings of the suspected firer is obtained by thoroughly washing his hands with warm water and subjected to the above tests.
Another modern method is by utilizing SEM-EDX. The suspected gunshot particles on the hands of the shooter are collected by means of a specialized GSR collection kits which contains stubs, gloves, plastic containers etc. The forefinger and its adjoining area, the palm are pressed with stubs after which the stubs are packed taking all the legal formalities. The stub is analyzed under SEM-EDX for gunshot residue.
Entrance wound is recognized by its inverted margins, the presence of scorching, blackening, tattooing, dirt ring, size and the number of wounds. The inversion of the edges at the entrance is caused by the projectile, which draws the skin inside. The dirt-collar and contusion ring are often noticed on the entrance side of the wound. The dirt ring is formed by the deposition of graphite, grease and dirt present on the bullet. The contusion ring is due to the impact of the projectile on the surface around the wound. When the muzzle of the gun is held in contact with the skin, the surface may be torn and lacerated, and powder marks on the surface may be entirely absent, due to their having entered the wound. Marks or imprint of wads may be found at the entry of a shotgun injury. The diameter of the entrance wound is usually smaller than the diameter of the bullet. This is due to the elasticity of the skin. The shape of the entrance wound may be round or oval. When the projectile enters the body at right angle to the surface, usually a round hole is formed. If it enters at an angle, an oval shaped hole is formed.
Exit wound is recognized by the absence of various marks found around the entrance wound such as presence of inverted edges of the skin and the shape and size of the wound, close range firing effects such as burning / scorching, blackening, tattooing around the wound. The edges of the wound are averted. The size of the exit wound is generally larger than the entrance wound or even size of the projectile. This is due to the deformation of the projectile and the tissues it gathers around it. There may be more than one exit holes for one entrance wound, especially when a bone has been struck, pieces of bone may be put into motion or the bullet may get fragmented. The bleeding is much more at the exit wound.
e pattern, however, must be available for study and the concerned weapon and ammunition must be obtained for test firing. The same gun and the same kind of ammunition are used to test fire at different measured ranges to match with the pattern revealed in firearm offence under investigation.
Exit wound is recognized by the absence of various marks found around the entrance wound such as presence of inverted edges of the skin and the shape and size of the wound, close range firing effects such as burning / scorching, blackening, tattooing around the wound. The edges of the wound are averted. The size of the exit wound is generally larger than the entrance wound or even size of the projectile. This is due to the deformation of the projectile and the tissues it gathers around it. There may be more than one exit holes for one entrance wound, especially when a bone has been struck, pieces of bone may be put into motion or the bullet may get fragmented. The