Micro-CT analysis of gunshot wounds for estimating the firing range

Background: Estimation of the firing range is often critical for reconstructing gunshot fatalities, where the main measurable evidence consists of gunshot residue (GSR). Aim of the study: The aim of the present study was to create an experimental protocol for the production of gunshot wounds on human skin sections subsequently examined by innovative radiological techniques (multi-slice spiral computed tomography- MSCT, and micro-CT) In order to determine the firing distance. Materials and methods: Human legs, surgically amputated, were cleaned of dried blood and any other contaminants and cut into sections of approximately 6 cm in length. Firing was carried out perpendicularly at distances of 5,15, 23,30, and 40 cm, using a 7.65-mm pistol loaded with jacketed bullets (10 replicates were performed for each distance). Uninjured skin sections were used as controls (n = 10). Each leg section was examined by both MSCT and micro-CT, and 3D-CT reconstructions were created. Reformations of each sample were analysed by means of a densitometric and imaging analysis software in order to identify and characterise the distribution of the GSR (expressed as percentage area). Results: Only in near-contact wounds (distance = 5 cm) a ring of radiopaque material was evident using MSCT, while at greater shot distances only smaller and individual particles were visible. At micro-CT analysis, the GSR particles were distributed on the skin around the entrance hole, inside the cavity and in the fatty tissue. Their radiological detection, which progressively decreased increasing the firing range, allowed a good discrimination of the firing distances tested in the present study. Conclusions: Micro-CT analysis proved to be an objective, reliable, rapid, and inexpensive tool for estimating the firing range