An Investigation into inorganic gunshot residue (IGSR) using Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray (EDX)

Harrington, Georgia (2021) An Investigation into inorganic gunshot residue (IGSR) using Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray (EDX). (MSc(R) thesis), Kingston University, .


Gunshot residue (GSR) is the debris that is expressed from a firearm when it has been discharged. A series of experiments were carried out following a range of shooting and transfer studies using SEM/EDX to detect inorganic gunshot residue.The initial investigation focused on the transfer of GSR particles on clothing from the firer of a Ruger semi-automatic rifle, using CCI standard velocity .22” long rifle round nose cartridges. Following discharge of the firearm, person to person contact was initiated with a non-firearm user not present in the vicinity at the time of the shooting. This resulted in the transfer of GSR from the shooter to the test subject, but with a reduced likelihood of three component particles (barium, antimony, lead) being detected. The total number of particles consistent with GSR transferred ranged from 112 to 302. Out of those particles, only 2 to 14 were three component GSR particles.Further experiments carried out at the ballistics and forensics investigation unit at An Garda Siochana, investigated the composition of GSR in a firearm that discharged combinations of Wolf and Fiocchi 9 mm ammunition. From the particle compositions found it was possible to identify which ammunition had been fired last due to the percentage of SbBa particles present. The distance GSR travelled from several different calibre firearms was assessed by examining targets over ranges of 2-10 metres. These experiments suggest that particles consistent with GSR can travel up to 10 metres from the firearm but characteristic three component particles only travelled 10 metres from a 12-gauge shotgun. Conversely, most three-component GSR particles from the other firearms only travelled up to 3-4 metres. All ammunition types had at least one three component particle at 4 metres, but the highest levels were detected at 2 metres The analysis of evidence from the three studies provides useful information forwhich observation should be considered. Study one highlighted how important the transfer of GSR can be, the evidence suggests that significant one and two component particles can be transferred directly from a firer to a recipient. If largeamounts of GSR particles are directly transferred, then it can be assumed indirect contact or presence when a weapon was discharged would also lead to the recovery of GSR particles. Study two allows a link between ammunition and weapon to be established, by looking at the chemical composition of the particles from both cartridge case and gun barrel we can identify component elements within the particles. The analysis suggests that it’s possible to distinguish between types of ammunition, which would provide important evidential information when recovery of GSR has been carried out. Study three provides evidence that suggest GSR particles can travel up to 10 metres from a firearm though typically three-component GSR particles will only travel to around 3 metres. These results directly link to study one, and relate to the transfer of GSR, proving that being in the vicinity of the discharge of a weapon canlead to the presence of those particles. Together the results from these studies can assist with the interpretation of GSR evidence.

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