Determination of gunshot residues with image analysis: an experimental study

In firearm injuries, assessment of the firing range and determination of entrance and exit wounds are important. For this reason, evaluation of the amount and distribution of gunshot residues (GSRs) is necessary. Several methods and techniques for GSR analysis have been developed. Although these methods are relatively sensitive and specific, they may require expensive dedicated equipment. Therefore, a simple, easily applicable, more convenient method is needed. A total of 40 experimental shots were made to calf skin from distances of 0, 2.5, 5, 10, 20, 30, 45, and 60 cm. Eighty samples were taken from the right and left sides of the wounds, and Alizarin Red S dye staining was performed. The amounts of GSR particles were measured with image analysis. GSRs were detected in all shots. The mean size of the distribution area of barium and lead elements around the wound had a significant negative correlation with increasing shooting distance (r = -0.97, p < 0.001). As the distance increased, the amount of GSR decreased, and this decrease rate was nonlinear. Variance analysis suggested significant differences between data groups depending on range (p < 0.001). The image analysis method may solve some of the standardization problems for evaluation of GSRs. GSR detection with the image analysis method does not require experienced personnel and may be a suitable method for scientific studies and for routine purposes.