A SEM image of a gunshot residue particle.
Gunshot residue kits are analyzed to determine if an individual was in the vicinity of a discharged firearm. The presence of GSR on a person's hands indicates that person discharged a firearm, was near a firearm when it was discharged or touched an object with gunshot residue on it. The gunshot residue kit contains two stubs with carbon tape adhesive that are used to tape lift the palm and back surfaces of a shooting suspect's hands. Since shooting victims are already connected to the discharging of a firearm, gunshot residue kits cannot usually provide any additional information to an investigation and are not routinely analyzed.
The stubs of the gunshot residue kits are analyzed for constituents of gunshot residue, namely the elements lead (Pb), antimony (Sb) and barium (Ba). These three elements originate from the primer of most firearm cartridges. Analysis is performed on a scanning electron microscope with x-ray detector (SEM/EDS).The Missouri State Highway Patrol Crime Lab can supply gunshot residue kits to law enforcement agencies in Missouri free of charge.