The Long Range Deposition of Gunshot Residue and the Mechanism of Its Transportation

Abstract

Tests were performed in an indoor firing range to establish the distance gunshot residue can travel following the discharge of a firearm. Sample collection devices were positioned at the firearm's ejection port and horizontally positioned down range up to a distance of 18 m. The collection devices were analyzed for gunshot residue (GSR) using scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDX). The area of highest GSR particle deposition was observed to be 13.5 m downrange of the firearm, however small numbers of particles were also found at a distance of 18 m. A target cube at a distance of 18 m was used to separate GSR particles travelling on the bullet from those travelling diffusely in the broad plume of gases emitted from the firearm. It was found that GSR particles travel in close association with the projectile as it was observed that the concentration of GSR particles on the rear target was an order of magnitude higher than the concentration on the forward target. GSR particle numbers cannot be used to distinguish between a shooter, an individual near the path of the projectile, or a shooting victim.