Firearms & Toolmarks

The Firearms and Toolmarks section is responsible for the examination of firearms, bullets, cartridge cases, ammunition components, tools, toolmarks, defaced serial numbers on firearms, and fabrics with bullet defects to determine approximate distance.

The manufacturing process of parts (e.g., firing pin, barrel, breech face), and subsequent finishing processes, will leave imperfections and irregularities at the microscopic level on the surfaces despite rigorous quality control measures. These microscopic dents, burrs, and blemishes are transferred to ammunition components in a repeating pattern and examined using specialized comparison stereomicroscopes. The results can establish a link between a particular firearm and the fired ammunition.

Firearms are examined to determine if they are functioning properly, and test fired into a large water tank. This provides exemplars (bullets and cartridge cases) from the firearm that may be compared to ammunition components from a crime scene. If a firearm has an obliterated serial number, a chemical restoration process can be utilized to potentially restore the serial number.

Cartridge cases from crime scenes and test fires are entered into the Bureau of Alcohol, Tobacco, Firearms, & Explosive’s (ATF) ballistic database, the National Integrated Ballistic Information Network (NIBIN). This 3D technology can provide investigative information and connections to violent crimes across jurisdictions.