Firearms Examinations

A firearms examination, sometimes called firearms identification, is the process of analyzing fired ammunition components (like bullets or cartridge cases) to determine whether or not they were fired in the same firearm, or if they were potentially fired from a submitted firearm (source determinations). The individual, microscopic markings a firearm leaves on ammunition when it's discharged make this possible.

Here's how those marks are created and analyzed:

• During the firing process, internal components of a firearm such as the breechface, firing pin, and barrel rifling can impart microscopic toolmarks on ammunition components.
• These microscopic markings (which can be both class and individual characteristics) can be created during the manufacturing process, along with resulting from wear, use, and abuse of the firearm.
• A comparison microscope is the primary tool firearms examiners use to compare these markings. By comparing the microscopic features on test-fired and evidence ammunition components, an examiner can reach source determination conclusions including identifications, eliminations, and inconclusives.