Comparison of SEM-EDX and ICP-MS for the analysis of gunshot residues after burial: An experimental study

Gunshot residues (GSR) analysis can be valuable in a forensic context for distinguishing entry wounds from exit wounds, especially in cases when body alterations prevent macroscopic analysis. Several studies have demonstrated its usefulness in various contexts. However, few studies have examined the retention of GSR under environmental conditions particularly after burial. The primary objective of our experimental study is to investigate the retention of GSR after burial and decomposition by using two techniques: SEM-EDX and ICP-MS. Our secondary objective is to determine whether it is still possible to distinguish the entry wounds from the exit ones after 2 months of burial. For this study, we used a bovine model (cow feet), and fired with 7 mm semi-jacketed bullets. We formed several groups, including 3 control groups that hadn't been shot (buried for 2 days and 60 days and one unburied group), 3 test groups that had been shot (one unburied and two buried that were exhumed after 2 days and 60 days of burial). The results of our study show that both SEM-EDX and ICP-MS were suitable for detecting particles characteristic of GSR, after 60 days of burial. However, only SEM-EDX could differentiate easily the entry wounds from the exit ones. Our experimental study demonstrates that SEM-EDX analysis is suitable in cases where the discovery of a buried body doesn't allow the macroscopic determination of the ballistic trajectory.