Finding GSR evidence on used towels

Abstract

When a firearm is discharged, gunshot residue (GSR) is produced and may be deposited on a shooter’s body and his close vicinity. The tendency of GSR to drop off easily from the shooter may hinder forensic detection; this well-known phenomenon is accelerated by various common physical activities so that the number of particles detected on a suspect decreases over time. After shooting incidents, suspects will often try to cover their tracks by taking a shower. In these cases, it was assumed that no GSR will be detected upon examining the suspect's hand and hair. In the present study, we provide a way to overcome this loss of evidence by taking advantage of another occurrence, namely secondary transfer. Our participants were asked to take a shower after shooting a firearm. Samples were thereafter collected from the used bath towels and were found to contain up to a few dozen particles characteristic of GSR, including very large particles (>45 µm). The detection of GSR on a suspect's towel may provide significant forensic evidence aiding an investigation. When a shooter tries to remove evidence by taking a shower, sampling the towels that he may have used can preserve important evidence and connect a suspect to a shooting incident.