When should gunshot residue be collected for the best results?

Gunshot residue (GSR) testing is crucial in forensic investigations, particularly in determining whether a person has discharged a firearm. The efficacy of GSR analysis is highly dependent on the timing of the collection of evidence. Collecting gunshot residue as soon as possible after the discharge increases the chances of obtaining a suitable sample, as the residue can dissipate or be cleaned off through various physical actions.

Choosing to collect GSR preferably within three hours of the discharge is based on studies indicating that the residues diminish in quantity and can even be removed by activities such as washing, rubbing, or simply by the passage of time. This time frame allows investigators to effectively gather and analyze samples that are more likely to yield conclusive results linking a suspect to a shooting incident.

This is why the timing of collection is emphasized. Gunshot residues can adhere to the skin, clothing, and surrounding surfaces, but these residues can degrade or be lost with time and activity. Therefore, the correct approach is to prioritize GSR collection as soon as feasible, ideally within a few hours after the event has occurred.