Passive Exposure and Persistence of Gunshot Residue (GSR) on Bystanders to a Shooting: Comparison of Shooter and Bystander Exposure to GSR

Abstract Gunshot residue (GSR) particles released from a firearm at the time it is discharged may be deposited onto nearby surfaces including the hands and clothing of the shooter and any bystanders. This study measured the relative amount of GSR detected on the shooter and on three bystanders in close proximity. Test-firings were conducted in duplicate using five different handguns with ammunition containing conventional lead, barium, and antimony based primers. Samples were collected from the right hand of the shooter 15 minutes after discharge. Bystanders were sampled 15 minutes after discharge and 2 hours after the initial sampling. A scanning electron microscope with an energy dispersive X-ray detector was used to analyze the samples. A high variability of GSR deposition was observed between firearm/ammunition combinations and between replicate firings. In some instances bystanders had similar concentrations of GSR on their hands to the shooter, making it impossible to distinguish between the two on the basis of particle numbers. Furthermore, after an additional 2 hours, most of the bystanders who initially had GSR particles on their hands had lost them through routine activity. The loss was comparable to what was expected from the hands of shooters based on information published in the literature.