Ballistics

Abstract

This paper will identify what ballistic examiners do when they look for when they exam ballistic evidence. Also the paper explains how bullets are not the only thing that is needed to match a weapon to its bullet, casing are used as well. New technology's are discussed as well and how they work.

Forensic Study of Ballistics

Firearm ballistics is a very astringent forensic science. The study of firearm ballistics is process that is ever-changing and most times crucial to the conviction of criminals that committed crimes with firearms. A bullet matching the rifling of a firearm and the firearm itself would usually suffice, but if the bullet can not be found the cartridge of the bullet would be just as effective. Firearm ballistics is an important part of the criminal investigation process when a firearm is used to commit a crime.

Once a bullet, cartridge case, and weapon are collected from a crime scene and delivered to the lab it begins the process of being compared together. The first thing that is examined is the caliber of the weapon and bullet (Doyle, 2005). If the two calibers do not match then that bullet was not fired from that weapon. The way that caliber is determined is through "rifling" of the barrel (Meyer, Ronald "personal communication," May 4, 2005). The rifling is the process in which firearm manufactures hollow out the barrel of their weapons and create spiral grooves in the barrel (Meyer, Ronald "personal communication," May 4, 2005). The surfaces of these grooves are called lands and the measuring of two opposite lands determine the caliber (Meyer, Ronald "personal communication," May 4, 2005). For example, if the distance of the lands were fifty millimeters apart the caliber of the weapon would be .50 caliber weapon. Also weapon manufactures use spiral grooves that impact a clockwise or a counter clockwise spin when they rifle out the barrel of the weapon (Meyer, Ronald "personal communication," May 4, 2005). The way forensic examiners compare the bullet to the rifle is to conduct an experiment which the examiners will fire bullets through the weapon in question into a water tank then compare the striations of the bullets to the striations of the bullet found at the crime scene (Doyle,2005). Striations are markings that are left on the bullet from the imperfections of the rifle impressions (Doyle, 2005). After examining the striations on the bullet from the crime scene and the test bullets a match will hopefully be made which would link the weapon to the crime scene or eliminate the weapon from the crime scene. If a bullet can not be found at a crime scene or the bullet that is found is far to damaged the bullet casings can be just as affective as "fingerprinting" a weapon to the crime scene.

When a bullet is loaded into the weapon the possibility of unique "fingerprinting" marks are left on the bullet cartridge known as chamber marks (Doyle, 2005). The chamber outer walls can leave marks on the cartridge when loaded and removed from the chamber due to the roughness of the chamber (Doyle, 2005). Usually, marks are left on the cartridge after the bullet has been fired (Doyle, 2005). The reason being is because the cartridge expands when fired and the imperfections of the chamber will leave unique marks on the cartridge (Doyle, 2005). Another unique feature that can be left on a cartridge is a firing pin drag mark (Doyle, 2005). A firing pin drag mark occurs when the pin strikes the primer of the