How Ballistic Identification Works

As shown in Figure 1, a firearm has a number of basic components. There is the barrel/firing chamber, where the cartridge will pass through when discharged. You also have barrel rifling, which are grooves inside the barrel. At the rear of the barrel/firing chamber is the breech face, along with a firing pin that strikes the cartridge through a hole in the breech face and causes the cartridge to discharge. The ejector removes the shell casing from the firearm.

Figure 1

Ballistic identification evaluates markings on bullets and/or cartridge casings made by a number of these components. The firing pin, barrel rifling, breech face, and ejector all leave unique markings on the projectile. Some can be seen with the naked eye, while others require more sophisticated viewing methods. By analyzing these markings, you can identify the bullet/cartridge casing/firearm "fingerprint" and match it to other information.

Current technology uses light angles and several variations of scanners and image capture techniques to take a digital image of the bullet or cartridge casing. The technology then searches a database for possible comparable matches, and a forensic examiner evaluates the potential matches.