It is a well-known fact that a wide variety of firearms like shotguns, rifles, revolvers, pistols, illegally manufactured firearms are being increasingly used in heinous crimes involving murders, dacoities, robberies, riots, and encounters. Convictions have been awarded and maintained in many cases when they were solely based on a firearm basis, hence it needs to be collected & interpreted properly.
Firearm evidence can help to:
1) Decide whether, the given incidence is a case of homicide, suicide, accident, or self-defense.
2) Verify various versions of the witnesses.
3) Establish the authenticity of the alleged case history.
4) Determine the sequence of events.
5) Establish the number of firearms used in an incidence.
There are several cases when victims of gunshot injuries survive for some time before their death. Survival periods have been recorded for a few minutes to a few years, depending upon the locations of the wound and the extent of the injury. When a victim survives, though it is of paramount importance to provide him medical attention and it is almost equally important to collect and document the used firearm and related evidence available either on the body of the victim or elsewhere.
Gunpowder is not only used in fireworks but also muzzle-loading guns in India and serves as evidence of great importance.
In a murder trial, the medical witness deposed that blackening around the wound was due to black powder and could not be caused due to smokeless powder. However, this deposition is not correct since both types of powder could cause blackening around the wound, of course with different shades of blackening.
The defense argument that gunfire injuries on the person of the victim were caused by a cartridge containing gunpowder as a propellant and the cartridge allegedly fired by the accused contained smokeless powder hence the accused could not be the murderer. This contention resulted in the acquittal of the accused.
On an appeal, the High Court withheld the acquittal based on the submission by the Ballistic expert that blackening may also be caused by the cartridges containing smokeless powder.
• Position of Firearm
In an interesting alleged suicide case, the firearm was found placed on the right-hand side of the victim whereas the victim was known to be left-handed. The obvious conclusion is that it could not be a case of suicide. Further investigation revealed this to be a case of homicide.
Normally a person who commits suicide selects a convenient site such as the temple, mouth, and under the chin. An entry wound on the back of a person would be indicative of a case of homicide as no one committing suicide will select such an unusual site which is not only inconvenient but impracticable also. It is very inconvenient to fire the self from the middle of the backside and almost impossible to do so in a horizontal direction while pressing the weapon uniformly against the back skin and firing the weapon by pressing the trigger.
• Range of Fire
The range of Fire is also an important factor deciding the nature of the case. A person killing himself will not shoot from a far distance. Number of Entry and Exit wounds.
Several entrance holes in the event of firing are usually an indication of the number of rounds that had hit the victim. There may be a situation when a soft nose bullet may get fragmented before entering the body on account of shrinkage porosity. In a homicide case, the deceased was having three entry wounds of sizes two centimeters. The claim of shooting the victim thrice was overruled as the postmortem doctor recovered only one lead core, one jacket, and three unevenly fragmented lead pieces. The total weight of these three pieces had been 11 gms approximately which was well within the weight of a .315 bullet.
In addition to this, this was no implication of any of the ingredients of the bullet. Therefore, it was concluded that injuries could have been caused as a result of the penetration of different fragments of the same bullet.
Evidence in case of non-recovery of weapons
Generally, the weapon used in the crime gets recovered but it may not happen in every case. In the case where the weapon is destroyed purposely or disposed – of, the recovery of the used firearm may be difficult or impossible. In a particular murder, the recovery of the firearm could not be made from the suspect. The house of the suspect was searched for recovery of the firearm which proved to be a fruitless exercise. However, some fired bullets lodged in a practice board were recovered luckily.
Experts could establish similarities between the two sets of bullets, i.e., one set consisting of bullets used in the crime and the other set recovered from the house of the suspect. The striation marks and firing pin marks could easily be helped in matching the bullets.
Penetration of Shots in different regions of the body
Inference regarding the number of shots fired is drawn usually from the number of areas of impact. Particular caution is required in case of an injury on the palm of a hand which is generally caused as a defense wound as illustrated by a case below. In one case a victim received an entrance wound of about 4 cms on the palm of his hand with a corresponding exit wound on the back of it.
In addition, he had several perforations on the chest region which had spread over it. All these injuries were caused as a result of firing off one round as the man on seeing his adversary with a country-made pistol pointed towards him from a close range exposed his palm in defense which resulted in an entrance wound from a close range from to his palm and the shot which got spread after exiting through the back of it, made multiple wounds in the chest region while he was trying to get up from lying position.
Blank Cartridges and Fatal Firearm Cases
Bank cartridges are used only for making loud noises. It is generally believed that Blank Cartridges are incapable of inflicting fatal and grievous injuries because they do not contain projectiles. Blank cartridges, however, can cause fatal and grievous injuries from a close range.
Evidence Related to Firearms and their Examination
A firearm can be identified on its class and individual characteristics. It bears various markings by the manufacturer for identification of caliber, design, type, model, firing mechanism, number of lands and grooves, etc. these markings are known as class characteristics.
These markings can help in identifying the owner. In the case of cartridge case type, shape, design and other formation-related characteristics like substances of the cartridge case, printed description on the base of the cartridge case, etc. are its class characteristics.
Besides the class characteristics, there are several other marks, which form on the surface of the cartridge case as well as the bullet. These types of markings are known as individual characteristics of a particular firearm and are also termed accidental markings.
These markings are of different types:
• Firing pin marks
• Breech face marks
• Ejector and extractor marks
• Chamber marks
• Other marks
Firing Pin Marks
When we pull the trigger a pin-like structure hits the percussion cap of the cartridge. This pin-like structure is known as a firing pin. In revolvers it is present on the hammer, in shotgun and rifles it is on the breech block, or in semi-automatic and automatic guns it is on moving breech block.
When the firing pin hits the percussion cap of the cartridge case it forms a depressed creator-like structure which is known as firing pin marks. There are differences in the shape, size, and finishing marks of the firing pin.
Breech Face Marks
The surface opposite to the chamber and towards the firing pin is known as breech face whose main work is to maintain the cartridge at its position during firing. At the time of the firing, there is the burning of the propellant produce gases which help in the propulsion of the projectile at the muzzle end, and on the other hand, it also pushes the cartridge case towards the breech face. As a result, all imperfections are imprinted on the base of the cartridge case. These marks are known as breech face marks.
Extractor and Ejector Marks
In modern firearms, there is the system of extractor or ejector for the removal of empty cartridge cases from the chamber. With the help of the extractor, the cartridge case was removed by pulling it towards the backside. After removing the cartridge case from the chamber, there is the ejection of the cartridge case with the help of the ejector. Generally, the ejector system is absent in revolvers.
Impurities are also present on the surface of the extractor and ejector which imprint striation marks on the surface and rim of the cartridge case during removal of the case. Therefore in comparison microscope, these marks compare by their size, shape, position, and other individualized characteristics.
After firing the explosion of propellant materials make forceful contact between the side surfaces of the cartridge case and the internal surface of the chamber. Due to this, all the characteristic features of the internal surface of the chamber imprint in the form of indented marks on the sides of the cartridge case. These marks are known as chamber marks.
The comparison of these marks can also be done with the help of a comparison microscope by using questioned and standard samples.
These marks are generally considered magazine marks, slide drag marks, etc.
Examination of the Fired Bullet
In the case of a bullet, its shape, size, type, weight, and caliber are class characteristics whereas scratch and friction marks present on the surface of the bullet are its characteristics. Examination of the bullet is based on the determination of caliber, type, model, etc. of a particular firearm. By using the standard bullets obtain from controlled fire from a suspected firearm of a case bullet, we can compare it from a case bullet and done individualization of a bullet. In the case of the shotgun, determination of bore and if the slug is present then it can compare with the sample obtained from controlled fire from a suspected firearm.
When the bullet comes out of the barrel, the imperfections and roughness are present on the internal surface of the barrel from the impression marks on the surface of the bullet due to the friction. The nature of the indented marks is three-dimensional and under the microscope, these look like the striations that are why these marks are known as striation marks.
Land and groove containing barrels produce more clear marks. During the comparison of striation marks present on both the samples, there is the verification of corresponding and continuity. This type of matching is known as composite matching. In the state of a positive matching, it can be said that the case bullet is fired from a suspected firearm.