When a handgun is fired the detonation of the cartridge and gas leakage around moving gun parts, in addition to blow-back from the muzzle, carries small particles (gunshot residue: GSR) to the shooter's hand. Characteristic particles (originating from and depending on the type of cartridge primer) can contain elements like: lead, barium, antimony, copper, strontium, and mercury.
Sampling the hands of a person suspected of having recently discharged a firearm makes it possible to ascertain such traces later in a laboratory examination. In the cap of each tube in this gunshot residue set, an aluminum "stub" is fitted. This stub has a black, electrically conductive adhesive layer, protected with a cover. After removing the cover, the upper side of a person's hand is sampled all over (by dabbing) with the stub, the cap replaced on the tube, and the tube labeled.
In the laboratory, the stub is removed from the cap and placed directly into a scanning electron microscope with EDX facility. Due to the electrically conductive layer, no coating with carbon is necessary. The particles collected on the adhesive are then detected and their elemental composition is determined (by analysis of the X-ray radiation released by the particles when they are hit with a focused electron beam).