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FBI Laboratory seal

FBI Laboratory heading

Graphic for Firearms-Toolmarks Unit


The Firearms-Toolmarks Unit receives and examines evidence related to firearms, firearm components, ammunition, ammunition components, tools, and toolmarks. Evidence in a typical case may include a number of recovered rifles, pistols, shotguns, silencers and other muzzle attachments, magazines, holsters, and a variety of fired and unfired cartridges. Lead and other metal fragments, shot wads, shot cups, and bullets removed from bodies at autopsy are also frequently received items in firearms-related casework. Evidence submitted in toolmark cases may include screwdrivers, scissors, knives, pliers, wrenches, crowbars, hammers, saws, wire, sections of sheet metal, chains, safety-deposit boxes, human bone or cartilage, plates, locks, doorknobs, bolts, and screens.

Forensic firearms examinations are based on firearms identification, which involves the identification of a bullet, cartridge case, or other ammunition component as having been fired by or in a particular firearm. Firearms examiners microscopically compare bullets and ammunition components to each other as well as to any number of firearms to determine whether an association exists between or among items submitted as evidence and items whose origins are known. Similarly, forensic toolmark identifications involve the identification of a toolmark as having been produced by a particular tool to the exclusion of all others. Examiners compare the micro- and macroscopic features of toolmarked items with known and questioned tools that may have produced them.

Tests and examinations routinely performed by Unit personnel include

—trigger pull tests,

—function tests,

—full-auto conversion tests,

—accidental discharge tests,

—shot pattern examinations,

—gunshot residue examinations,

—ejection pattern testing,

—trajectory analysis examinations,

—silencer testing, and

—serial number restorations.

Graphic showing pistol muzzle flash

Muzzle flash during the discharge
of a firearm

Graphic showing miscellaneous ammunition

Assorted ammunition evidence

Graphic showing gunpowder


Graphic showing trigger pull testing system

Trigger pull testing system

Graphic showing trajectory analysis at a crime scene

Trajectory analysis of the bullet
holes in an automobile

In addition to the Reference Fired Specimen File, the Unit maintains the Reference Firearms Collection, which contains over 5,100 handguns and shoulder firearms, and the Standard Ammunition File, a collection of over 15,000 military and commercial ammunition specimens of foreign and domestic manufacture.

Firearms examiners provide field support in FBI investigative matters and administrative inquiries, directing or assisting with the collection, preservation, and processing of evidence at crime scenes. In addition, Unit field teams provide crime scene reconstructions and analyses as needed, stateside or internationally, with designated response teams on standby rotation in the event of disaster in the United States or overseas.

The Unit also serves as a liaison with national and international forensic laboratories. Examiners from this Unit provide extensive training services, both general and specialized, to members of law enforcement agencies as well as to crime scene personnel and investigators. Training schools in trajectory analysis, gunshot residue analysis, firearms identification, and the identification of stolen motor vehicles are sponsored by the Unit on a yearly basis.

For more information about firearms evidence or the Firearms-Toolmarks Unit, see the Firearms Examinations section of the Handbook of Forensic Services and the Firearms and Toolmarks article in Forensic Science Communications.


Graphic showing a revolver

Graphic showing a rifle
Hand and shoulder firearms

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Information revised October 2000