Fundamental Studies of Gunshot Residue Deposition by Glue-Lift

Abstract

The mechanism of gunshot residue (GSR) deposition and its probing characteristics have been studied by the Glue-Lift collection of GSR and its identification by scanning electron microscopy and energy-dispersive X-ray analysis (SEM-EDX). By blocking alternately muzzle-blast residues and trigger-blast residues of shotguns, it has been shown that, if the firearm is thoroughly cleaned before the firing, the muzzle-blast residues seldom settle from the air onto the shooter's hands. Whereas the trigger-blast residues are literally blasted onto the immediate surfaces of the firearm and on both of the shooter's hands that are on the weapon. Therefore, the hand deposits are mainly the breech deposits. If the firearm is not pre-cleaned the residues of previous firings lodged as fouling in the interior of the gun are blown off rather irregularly through the breeches and the muzzle in the subsequent firings. These residues occasionally overlap with the fresh breech deposits of the shooter's hands. Color tests for residue developed with sodium rhodizonate have confirmed the basic mechanism of GSR escape through the breeches and the ejection mechanism of the close-breech weapons. The forced deposition of the trigger-blast residues is an advantageous as well as limiting process. The contrast of residue deposits on the back of a hand versus the palm, is due to shadowing of the residue particles by the hand grasp on the firearm. But these particles may also be transferred to the nonfiring hand by contact with a fired gun. Whether it is a handgun or a longarm, if the gun is pre-cleaned and the ammunition and the hand grasps remain unchanged, a fixed amount of residues is deposited per firing on the back of the trigger hand. This deposition, which takes into account all deposited particles containing one, two, and three characteristic elements of GSR (e.g., Pb, Sb, Ba), is a fundamental piece of information helpful for the reconstruction of a shooting.

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

“…The results provide strong evidence that secondary transfer mechanisms can result in the transfer of GSR particles to an individual who was not present when the firearm was discharged (research question one). Particles may be transferred to the hands of a second individual via an interpersonal (hand‐to‐hand) contact and also via a contact with a recently discharged firearm, the latter finding corroborating Basu et al . Contrary to investigations of potential GSR secondary contamination (Gialamas et al .…”

Distribution of gunshot residues – The influence of weapon type

“…This ''memory effect'' may explain why heavy metal containing particles are often detected on hands in examinations when it is known that ''clean'', ''lead-free'', ''green'' or ''non-toxic'' ammunition was fired. Such particles would then be the result of previous shots with conventional rounds (compare [29]). …”

“…However, this may be the only place where it is highly probable that the GSR particles reaching the hands of the shooter are predominantly derived from the last shot [29]. Thus, the trigger finger would be the area of choice for meaningful GSR sampling with the highest probability of particles being derived from the relevant shot.…”

“…Various ''glove'' or replica methods have been proposed to distinguish leftor right-handedness and even to give indications on certain weapon types (e.g. [29][30][31][32]). These methods normally involve taking a replica from each hand with some liquid polymer thatafter solidification -encloses the GSR particles that are then visualized by a color reaction, usually rhodizonate.…”

Evaluation of gunshot residue (GSR) evidence: Surveys of prevalence of GSR on clothing and frequency of residue types

“…To assign P(E/Hp) the question asked is: What is expected in this situation if X is the person who fired the shot? There are quite a number of articles giving numbers of characteristic particles recovered from hands and clothing of shooters in various situations [10,[19][20][21][22][23][24]. The most recent and comprehensive study was carried out by Brozek-Mucha [19] who examined the deposition of characteristic particles on the hands and clothing of five persons who had each fired one shot from a semiautomatic pistol using Luger 9mm FMJ Sellier & Bellot ammunition, and the persistence of the particles over nine time intervals ranging from 30 to 240 minutes.…”