An experimental investigation of the indirect transfer and deposition of gunshot residue: Further studies carried out with SEM-EDX analysis

Experiments were undertaken in order to explore the potential for gunshot residue (GSR) particles to undergo tertiary transfer, and to be deposited on individuals in the vicinity of a firearm discharge. Samples were taken from hands following a series of test-firings. SEM-EDX with automated detection and analysis software was used to determine the presence of GSR on these samples. As many as 22 particles were found to have undergone tertiary transfer via a series of handshakes following a firearm discharge. In one run, a particle measuring 49.19 μm was recovered from a tertiary transfer recipient. Significant numbers of particles were also recovered from bystanders, with as many as 36 being detected on a sample taken from an individual who was in the proximity of a firearm discharge. The implications of these observations for forensic investigations are considered. In particular, the need to prevent unwanted transfer during the collection phase is highlighted, and the importance of acknowledging the possibility of secondary and tertiary transfers when reconstructing firearms incidents is also stressed. Experimental studies offer a means of improving our understanding of the dynamics of GSR transfer and deposition, and assisting the forensic reconstruction of firearms incidents.