What are the factors that go into the comparison of cartridge casings?

Comparison of bullets involves “class” and “individual” characteristics. These characteristics are based upon “striae” left on the bullet as it passes through the barrel. Class refers to the type of caliber and rifling. Rifling pattern may turn to the right or left, with a given rate of twist.

What is the biggest problem in making an identification in bullets?

One of the biggest problems in making an identification is that few evidence bullets are submitted intact. Most are badly distorted, wiped and/or fragmented.

What effect does the firing pin have on the cartridge case?

In all ammunition, a primer in the base of the cartridge is struck by the firing pin of the gun. The primer is ignited, which, in turn, ignites the gunpowder in the cartridge case. This action creates gases that push the projectile out of the cartridge case, along the barrel, and out of the weapon.

What are the limitations of microscopic firearms analysis?

The biggest limitation would be the condition of the evidence. If the evidence (bullets and cartridge cases) is too damaged or mutilated to reveal sufficient individual characteristics, then no comparison can be made. The lack of a suspected firearm also presents limitations for the examiner’s conclusions.

What are the two types of cartridges?

The ammunition used in a rifle or handgun is called a cartridge, and there are two general types of cartridges used by rifle and pistol shooters available today — centerfire and rimfire.

What is the difference between cartridge and case?

Cartridge: A unit of ammunition, made up of a cartridge case, primer, powder, and bullet. Sometimes incorrectly called a “bullet”. Cartridge case: The container for all the other components that comprise a cartridge. Sometimes incorrectly called a shell, shell casing, brass, or a hull.

Why is the cartridge case important in forensic science investigation?

If investigators recover bullets or cartridge cases from a crime scene, forensic examiners can test-fire a suspect’s gun to see if it produces ballistic fingerprints that match the evidence. A fired bullet with rifling impressions from the barrel of a gun (left). A fired cartridge case and fired bullet (right).

What is the purpose of firearms identification?

Firearm Identification is a sub-category of toolmark identification; which has as its primary concern to determine if a bullet, cartridge case, or other ammunition component was fired by a particular firearm.

What causes breech face marks in the cartridge head?

Breech face marks- These marks come from the area surrounding the firing pin of the gun. After the cartridge powder is ignited by the firing pin striking the primer cup, tremendous pressure is exerted in the chamber of the weapon, forcing the back of the cartridge case against the breech face of the weapon.