Which of the following best describes gun shot residue?

• A. A brand name of a cleaning solvent.
• B. A type of soil contamination in a crime scene.
• C. The powder residue left from firing a gun, used to infer firearm involvement.
• D. A feature of violent crime scene.

Answer: (C)

Gunshot residue is the powder and primer residue expelled when a firearm is fired. It includes tiny metallic particles from the bullet’s powder—often containing lead, barium, and antimony—that can settle on the shooter’s hands, clothing, or nearby surfaces. Detecting and analyzing this residue helps investigators infer firearm involvement at the scene, especially when combined with other evidence. However, its presence isn’t absolute proof on its own due to factors like distance from the muzzle, transfer to other objects, and time elapsed since the shooting. The other descriptions don’t fit what GSR is, since it’s not a cleaning solvent, nor soil contamination, nor a vague crime scene feature.