GSR deposition along the bullet path in contact shots to composite models

Abstract

In contact shots, all the materials emerging from the muzzle (combustion gases, soot, powder grains, and metals from the primer) will be driven into the depth of the entrance wound and the following sections of the bullet track. The so-called "pocket" ("powder cavity") under the skin containing soot and gunpowder particles is regarded as a significant indicator of a contact entrance wound since one would expect that the quantity of GSR deposited along the bullet's path rapidly declines towards the exit hole. Nevertheless, experience has shown that soot, powder particles, and carboxyhemoglobin may be found not only in the initial part of the wound channel, but also far away from the entrance and even at the exit. In order to investigate the propagation of GSRs under standardized conditions, contact test shots were fired against composite models of pig skin and 25-cm-long gelatin blocks using 9-mm Luger pistol cartridges with two different primers (Sinoxid® and Sintox®). Subsequently, 1-cm-thick layers of the gelatin blocks were examined as to their primer element contents (lead, barium, and antimony as discharge residues of Sinoxid® as well as zinc and titanium from Sintox®) by means of X-ray fluorescence spectroscopy. As expected, the highest element concentrations were found in the initial parts of the bullet tracks, but also the distal sections contained detectable amounts of the respective primer elements. The same was true for amorphous soot and unburned/partly burned powder particles, which could be demonstrated even at the exit site. With the help of a high-speed motion camera it was shown that for a short time the temporary cavitation extends from the entrance to the exit thus facilitating the unlimited spread of discharge residues along the whole bullet path.

MicroCT detection of gunshot residue in fresh and decomposed firearm wounds

“…In a recent paper, Groβe Perdekamp et al [20] have demonstrated that in contact shots fired against composite pig skin-gelatine models, GSR particles were detectable also in the distal sections of the missile track up to the exit hole, while in our study no GSR particles were visible within and around the exit holes. These apparent divergences might have been caused by the different experimental models used (composite pig skin-gelatine model vs. human calf sections) and by the longer muzzle-to-target distances tested in our study (5,15, and 30 cm), which probably avoided the massive invasion of combustion products along the wound track.…”

Wounding capacity of muzzle-gas pressure

“…A comparison of contact shots and shots from an intermediate range clearly showed that gelatine disruption was significantly more extended in contact shots. The five experiments with muzzle contact showed GSR along the bullet path, particularly in the first and last parts, which corresponds to findings by Lieske et al [17] and is systematically documented by quantification of GSR by Große Perdekamp 6 Mean values of the WP for diverse distances et al [18]. A distance of 2 or 4 m and also 10 cm to the model already changed the character of the gelatine destruction.…”

The secondary transfer of gunshot residue: an experimental investigation carried out with SEM‐EDX analysis

“…The forensic investigation of incidents involving firearms routinely involves attempts to detect gunshot residue (GSR) on samples taken from different surfaces. The results of GSR analyses are often used in crime reconstruction to determine a variety of details including the shooting distance/trajectory, the characteristics of the firearm/ammunition combination and the nature of wounds (entry or exit) . Meanwhile, the detection of GSR on a sample taken from the hands, face or clothing of an individual may indicate that an individual has been in the vicinity of a discharging firearm or has made contact with surface onto which GSR has previously been deposited.…”