Image analysis of gunshot residue on entry wounds - II - A statistical estimation of firing range

A statistical investigation of the relationship between firing range and th e amount and distribution of gunshot residue (GSR), used automated image an alysis (IA) to quantify GSR deposit resulting from firings into pig skin, f rom distances ranging between contact and 45 cm. Overall, for a Ruger .22 s emi-automatic rifle using CCI solid point, high velocity ammunition, the to tal area of GSR deposit on the skin sections decreased in a non-linear fash ion with firing range. More specifically there were significant differences in the amount of GSR deposited from shots fired at contact compared with s hots fired from distances between 2.5 and 45 cm; and between shots fired fr om a distance of 20 cm or less, with shots fired at a distance of 30 cm or more. In addition, GSR particles were heavily concentrated in the wound tra ct only for contact and close range shots at 2.5 cm, while the particle dis tribution was more uniform between the wound tract and the skin surfaces fo r shots fired from distances greater than 2.5 cm. Consequently, for future scientific investigations of gunshot fatalities, once standards have been e stablished for the weapon and ammunition type in question, image analysis q uantification of GSR deposited in and around the gunshot wound may be capab le of providing a reliable, statistical basis for estimating firing range. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.