Effects of carbonization on gunshot residue detection in an animal model

Abstract

The detection of gunshot residue (GSR) can be useful to determine if the wound has been caused by a firearm and it could help to differentiate the entry wound from the exit one. Carbonization is a good method for altering crime scenes. However, there are few studies in this specific context. The first objective of our study was to examine the persistence of GSR in wounds after carbonization. The second aim was to differentiate entry wounds from exit ones.

For the experiment, bullets were fired with a 22LR on sheep limbs at contact range.

The specimens were divided into four groups: two that weren't shot at (fresh and carbonized limbs) and two of shot limbs (one with carbonization and one without). Carbonization was performed in the open air using an accelerant.

Wounds were analyzed using Scanning Electron Microscopy with Energy Dispersive X-ray spectrometry (SEM–EDX) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS).

Lead, Antimony and Barium were observed using SEM-EDX only in the entry wounds, while lead was found in the exit ones. ICP-MS enabled the detection of these elements in the entry and exit wounds but predominantly in the entry ones. After carbonization we observed a huge decrease of GSR. With SEM-EDX most of the particles detected were only consistent with GSR. Anyway, the identification of GSR and the differentiation between entry and exit wounds were still possible with both techniques. Therefore, they are suitable for detecting GSR in carbonized gunshot wounds under the specific conditions of our experiment.