Analytical and quantitative concentration of gunshot residues (Pb, Sb, Ba) to estimate entrance hole and shooting-distance using confocal laser microscopy and inductively coupled plasma atomic emission spectrometer analysis: An experimental study

Abstract

The identification of gunshot residues (GSRs) on human body in firearm related fatalities may be essential for the evaluation of gunshot wounds and for the analysis of the shooting distance. The present study introduces the elemental analysis of the GSRs by inductively coupled plasma atomic emission spectrometer analysis (ICP-AES) performed on skin samples. ICP-AES was used to increase the accuracy of the analysis in gunshots fired from long and medium distance. In this experimental study, a series of 50 test shots have been performed in an open space with lateral wind protection. As target we used pig skin cut into 20cm×20cm squares. The firing distances were 0.2, 5, 50, 100 and 150cm. To exclude environmental contamination, each skin sample was carefully washed with deionized water and dried at room temperature in a closed box before the shooting test. We choose 9×21 and the 7.65mm calibers handguns, loaded with different ammunitions. At ICP-AES analysis a clearly decreasing trend in the quantity and the concentration of the different elements of GSR by increasing the firing distance for both the guns used in the test was evident for every portion of skin samples analyzed. The analytical results obtained by ICP-AES confirmed very high concentrations of Pb, Sb, and Ba in the close-range shots and low concentrations of these particles in the intermediate and distant shots. In particular, the concentration of Sb, Ba, and Pb was significantly different from loose values when the firing distance was 100–150cm for both the 9×21 and the 7.65mm calibers.