Firearm Identification is the procedure of examining the bullets and cartridge cases left at a crime scene to determine if they came from a particular firearm. The examination and microscopic comparison of fired bullets and fired cartridge cases to allow the expert to determine if a suspect firearm or firearms were or were not discharged in a shooting incident. Firearm examiners have attempted to determine the shorter position by the location of spent bullet casings. The use of ejection pattern studies we’re originally part of incident reconstruction and methods for determining shooter location. Continue to be explained in major crime scene examination books. Before firearms can be examined, Firearm evidence must be collected. When a crime is committed, crime scene investigation must look in and on floors, ceiling, walls, etc. To find fired Bullets and Cartridges cases. In inclusion, they must look for evidence that might contain gunpowder or other residues, such as clothing with bullet holes crime scene investigators begin a careful record of the individuals who handle or transport the evidence as it makes it’s way to the forensic laboratory, Where firearm identification occurs. Forensic scientists who analyze firearm evidence in the lab are typically called firearm examined.
The examination and microscopic comparison of fired bullets and fired cartridge cases allow the expert to determine if a suspect firearm or firearms were discharged or not. A list of potential firearms that could have discharged a bullet and a cartridge case can also be identified during the investigative stage in the absence of a suspect firearm. The distinctive of each firearm transfer to the cartridge case and bullet whenever the weapon is fired. This has been proven through physical sciences including physics, metallurgy, materials science, and metallography. The firearm examiner’s job begins when firearm evidence arrives at the lab from the scene of the crime. The forearm identification process consists of several steps. The examiner may need to remove trace evidence from a bullet or cartridge for analysis in another part of the job. Then the examiner evaluates the class characteristics of the evidence. The firearm examiner must take detailed notes during every step of the process. If the firearm evidence is used in a case that goes to trial, the firearm examiner may be required to testify in court about the work firearm evidence is among the most important evidence in many cases. Firearm evidence is usually encountered in crimes against persons such as assault, homicide and robbery but may also be found in other crimes such as rape, narcotics violations. While comparisons of bullets and cartridge cases to specific firearms are the most common examinations requested, other examinations are possible such as distance determination based on powder residue or shot spread examination of firearms for functioning or modification sequence of shots fired and trajectories list of possible weapons used, Serial number restoration and ownership tracing. Evidence of firing or handling a firearm may be detected through the analysis of gunshot residue collected from a person’s hands or other body surfaces.
A discipline of forensic science which has its primary concern to determine if a bullet, cartridge case or other ammunition component was fired in a particular firearm to the exclusion of all other.
A unit of armament made up of a cartridge case, primer powder and bullet.
The container for all other components that comprise a cartridge. Sometimes in correctly called a shell, shell c, using, brass, or a hull.
Purpose of Firearms Identification
Forensic scientists in the firearm and tool mark section practice firearms identification. They control if a bullet cartridge case or another shot component was fixed by a particular firearm. Firearm accessories benefit from knowledge and study of ballistics, the science of projectiles in motion in their work. The fingerprint recovery from the surface of firearms is done. Forearms are placed in a specially designed fume-hood designed to evenly distribute fumes instead of removing them.
Classifications of Firearms
On bullets, the class attribute is the rifling specifications of the barrel from which the bullet was fired. It includes the caliber number of lands and grooves, direction of twist of the lands and grooves, and widths of lands and grooves.
Principles of Firearms Examination
Firearm identification is founded on uniqueness. All objects can be from one another and the same is true for firearms legally for criminal investigators.
- Class Characteristics
- Firing impression
- Breech face marks
- Ejector marks
- Extractor marks
- Class Characteristics
These are the characteristics that remain constant for a class.
These are the exceptional characteristics that may establish the uniqueness of an object
Comparison of Firearms
Comparison of firearms cartridge cases and bullets can be done by following steps-
- Comparison of Microscope
- First, an exhibit is compared with a test sample or standard for class similarities and characteristics.
- If dissimilarities in class if characteristics are found or a general lack of good class characteristics are present no further comparisons may be necessary.
- When similar characteristics identified the examination progress to a final stage where an attempt is made to find a match in the individual characteristics.
- Test Bullets
These are the bullets fixed from the suspect firearm, in order to compare the test-fired bullet with the suspected bullet.
Steps of Conducting Test Firing
Water Bullet Recover Tank
The test bullet is fixed in closed container filled water. The muzzle of a firearm is placed on an open tube at the end of the container and a bullet is fired.
Bullet Catcher Collection Chamber
The chamber of the bullet catcher is filled with ballistic fibers of cotton, Which are usually used in bullet retrieval chambers. Ballistic fibers are non- flammable, so there is no risk of fire.
Types of Ballistics
There are three types of ballistics internal, external and terminal. Internal ballistics is the study of what happens within the barrel of a weapon from the moment the firing pin hits the primer to the time bullets exits from the barrel.
It’s a combination of two compound microscopes into a singular unit. The distinct feature of this microscope is the bridge that connects the two microscopes and made the visits of both the objective lens on a single eyepiece lens.
Classification of Rifles
All firearms, whether military assault rifles or civilian, pistols. These are classified into three broad categories- Simi automatic, fully automatic and other. The groupings are based on how the weapon loads and fires bullets into its chamber for the next firing.
Firearms are very commonly used by criminals in India. These Firearms include revolvers, pistols, shotguns, cabinets and machine guns of various types. The country made firearms are very frequently used in the criminal activities when a shooting incidence occurs, the investigating agencies collect the firearms-related exhibits from the scene of occurrence and send to the forensic science laboratory for further examination. An illustration of the field bullet in terms of its construction, caliber and the cartridge types possibly represented and it’s the manufacturer. A list of the brands and types of firearms that could have produced the general rifling characteristics observed in its surface. The interpretive potential of the fired bullet in terms of whether or not it bears sufficient microscopic marks for later comparison if as the suspect firearm is recovered. Firearms evidence can be recovered in a number of ways and areas. Firearms themselves can be recovered at shooting scenes by crime scene investigators and sent to the laboratory. Bullet evidence can also be obtained at autopsy or in an emergency room setting. In these cases, the sample should be marked as a biohazard and then sent to the laboratory.
Firearms Tool Mark Examination is a Forensic Science
This is achieved by using a combination of Class and Individual characteristics If no suspect firearms are imminent, the number of firearms discharged in an incident is usually able to be determined, along with how many times each was discharged.
Striation Marks on Bullets
Striations are the microscopic contour variations on the surface of the bullet. In firearms confirmation, the softer material is the bullet and the harder material is the gun barrel. Firearms examiners use the striations left on the fired bullet for their comparisons.
Striated Action Marks
These are common to cartridge cases that have passed through the action of an auto repeating firearm. Most chamber marks occur after the cartridge is fired. Cartridge cases expand when fired passing out against the walls of the chamber.
Q1. What is the identification of firearm with Cartridge Case and bullets?
Q2. What is used in the examination of bullets and guns?
Q3. What are the three materials from which cartridge cases are made up?
Q4.What is the principal of the firearm examination?
Q5. What is the purpose of firearm identification?