Gunshot Residue

During the discharge of a firearm, escaping gases from the weapon deposit gunshot residue (GSR) on the skin of the shooter’s hands, on the clothing of the shooter, and on other objects located in close proximity to the shooter. Included in this gaseous cloud of residue are particles composed primarily of primer residue. Primer compositions may vary with different types of ammunition and different manufacturers, but the most common constituents of primers have been lead styphnate, barium nitrate, and antimony sulfide. Analysis and characterization of the residue for the trace elements (lead, barium, and antimony) are used to indicate if a suspect has fired, handled, or been in close proximity to a weapon when it was fired.