Writer's Centre: CSI Dictionary: G

Gunshot residue (GSR)
Material propelled from the muzzle of a firearm when it has been shot. Most GSRs consist of lead, soot (graphite dust), barium, and antimony. When GSR is found on a person's palm, it generally indicates that that peron has handled a fired weapon. When it is found on the back of the hand, it generally indicates that the person has fired the weapon.