The role of the Firearm and Toolmark examiner is to examine evidence which otherwise would stand mute before the bar of justice.
By using a comparison microscope, a Firearm and Toolmark Examiner is able to compare bullets (from victims and crime scenes) and cartridge cases (from crime scenes) side-by-side against those test fired in guns submitted by various law enforcement agencies. The examiner can determine whether or not a bullet or cartridge case was fired from the gun in question by comparing the fine lines and markings on the surface. The examiner also does caliber determination on bullets, function and safe operation tests on firearms to determine if they are safe to shoot or could accidentally discharge.
By using a comparison microscope, an examiner compares the markings left at crime scenes by tools such as bolt cutters, screwdrivers, pry bars, knives, etc. to test markings made by the examiner using tools submitted by various police agencies.
Another duty of the examiner is to restore obliterated serial numbers on firearms or other items. After preparing the surface, the examiner applies different chemical solutions to restore the numbers.
The NIBIN database contains images of cartridge cases and bullets recovered at crime scenes, as well as cartridge cases and bullets from test fires of recovered firearms. As new images are entered, the system searches the existing database for possible matches. When the NIBIN system discovers a likely match, a firearms examiner must conduct a microscopic examination of the actual bullets and/or cartridge cases to make an identification.