Gunshot Residues

Abstract

Gunshot residue (GSR) or firearm discharge residue (FDR) is the debris created during the discharge of a firearm. The residues may be associated with the primer, primer cup, propellant, projectile (slug/shot), projectile jacket and lubricant, cartridge case, and firearm barrel. GSR arises from the cooling and condensation of the materials produced by the combustion reactions within the firearm and can be deposited on the firer, bystanders, and surrounding surfaces in the event of a discharge. The presence of particles characteristic or consistent with GSR may be used to show recent contact with a source of GSR, such as being in the vicinity of a discharge. It can be used to identify bullet holes, yield useful information as to firing distance, allow the identification of a suspect as having recently been in contact with a GSR source, and in some circumstances, may help distinguish suicide from suspicious death. This article details the formation of GSR, its deposition and transfer, as well as the various analytical techniques used to detect and differentiate it from non-GSR.