Antimony content of inorganic gunshot residue (IGSR) produced by 0.22 caliber rimfire ammunition having free-antimony primer.

In a recent paper published in Forensic Science International (FSI), Lucas et al. (2016) claimed that muzzle discharge of 0.22 caliber rimfire ammunition is more likely to incorporate particles from the bullet surface than those retained on the firearm and that characteristic particles containing Pb, Ba and Sb formed from known Sb-free primers are likely to be more prevalent in muzzle discharge. It seems that this claim is not based on sufficient experimental results.

Organic gunshot residues: Observations about sampling and transfer mechanisms.

This work aimed at studying the sampling, storage, transfer and persistence of organic gunshot residue (OGSR), mainly stabilizers, using liquid chromatography hyphenated to mass spectrometry. Collection using swabs and stubs was compared through sequential sampling in terms of amount of residues left on the hand of a shooter. While stubs collected nearly all residues, swabs left about 50% of the residues on the hands. Moreover, the study of storage conditions after sampling showed that stubs were more stable than swabs and could be held at room temperature without significant compound loss up to 2weeks. Then, shooting experiments were performed to evaluate transfer of OGSR. It was not possible to differentiate different brands of ammunition based on a single compound concentration. Moreover, a memory effect was identified when different ammunition was shot using the same firearm. Finally, various exposed skin surfaces and hair as well as clothing were sampled to estimate what surfaces might be the best targets for OGSR sampling by comparing results just after discharge and 2h after discharging a pistol. The results indicated that OGSR were more rapidly lost from hands than from clothing. Moreover, it was shown that the face and hair of a suspect might be contaminated through secondary transfer. Thus, OGSR might remain longer on other skin surfaces, hair and clothing than on the hands of a suspect. As a consequence, sampling should also include clothing, hair and face.

The influence of a possible contamination of the victim's clothing by gunpowder residue on the estimation of shooting distance.

A study was conducted to assess the influence of a possible contamination of the victim's clothing by gunpowder residue on the estimation of shooting distance. The study was focused on the scenario in which the contamination might be caused by the surface on which the shot victim could fall. Contamination of two types of textile was examined after contact with two types of surfaces. One round was fired above those surfaces (the line of firing parallel to the surface) prior to the contact. It was found that few gunpowder residue particles could be transferred to the clothing. These findings should be taken into account when interpreting results for shooting distance estimation in cases when a minute quantity of gunpowder residue particles is found around the bullet entrance hole.

A feasibility study on the use of double-sided adhesive coated stubs for sampling of explosive traces from hands.

A study was conducted to assess the applicability of double-sided adhesive coated stubs for sampling traces of TNT, RDX and PETN from suspects' hands. The double stage extraction method developed in the previous study for recovery of NG and 2,4 DNT in gunpowder residues sampled by double-sided adhesive coated stubs, was found to be applicable also for TNT, RDX and PETN. These explosives were analyzed using GC/TEA and IMS.

Application of lead isotope analysis in shooting incident investigations.

A study was conducted to examine the potential of the considerable variability of the lead isotope compositions in bullets (projectiles) and primers in shooting incident investigations. Multiple-collector inductively coupled plasma mass spectrometry (MC-ICP/MS) was used to analyze lead isotopic compositions in projectiles, cartridge cases, firearms discharge residues (FDR) in barrels of firearms and in the gunshot entries. .22 caliber plain lead and plated ammunition and 9 mm Luger full metal jacket (FMJ) ammunition were employed in shooting experiments using semiautomatic pistols. Cotton cloth served as the target material and two firing distances were tested; 1 cm (near contact) and 2 m distances. It was observed that various mechanical or chemical means of cleaning do not completely remove lead deposits ("lead memory") from barrels of firearms. Nonetheless, it was shown that analysis of lead isotopic composition may provide valuable evidence in investigating specific scenarios of shooting incidents. For instance in a shoot-out where several firearms and ammunition brands are involved, it may be feasible to point out which ammunition and/or firearm caused a particular gunshot entry if the ammunition brands involved (bullets and primers) differ considerably in their lead isotopic composition.

A novel method for extraction and analysis of gunpowder residues on double-side adhesive coated stubs.

A study was conducted to develop an efficient method for extraction and analysis of gunpowder (propellant) residues from double-side adhesive coated stubs, which are used for sampling suspects or their clothing for gunshot (primer) residues (GSR). Conductive and non-conductive double-side adhesives were examined, and the analysis was carried out by gas chromatography/thermal energy analyzer (GC/TEA) and ion mobility spectrometry (IMS). The optimal procedure for the extraction, as was developed in the present study, employs two stages: (1) extraction of the stubs with a mixture of 80% v/v aqueous solution of 0.1% w/v of sodium azide and 20% v/v of ethanol employing sonication at 80 degrees C for 15 min. and (2) residues from the obtained extract were further extracted with methylene chloride. The methylene chloride phase was concentrated by evaporation prior to analysis. Extraction efficiencies of 30-90% for nitroglycerine (NG) and for 2,4-dinitro toluene (2,4-DNT) were found. No significant interferences in the analysis were observed from the adhesives or skin. Interferences were observed in the analysis by the GC/TEA of the samples collected from hair. The method enables analysis of propellant residues on a double-side adhesive coated stub after it was examined for primer residues by scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX). Thus, the probative value of the evidence may be increased.

Vacuum collection of gunpowder residues from clothing worn by shooting suspects, and their analysis by GC/TEA, IMS, and GC/MS.

Experiments were conducted to collect gunpowder (propellant) residues from shooters' clothing by vacuum and to analyze them by gas chromatography/thermal energy analyzer (GC/TEA), ion mobility spectrometry (IMS), and gas chromatography/mass spectrometry (GC/MS). The residues were collected on fiberglass and Teflon filters using the portable vacuum sampler, all supplied with the IMS instrument. Several solvents were examined for the extraction of the propellant components from the filters. The extracts were centrifuged and/or filtered, concentrated by evaporation, and analyzed without any additional clean-up procedure. Based on the results of the study, an operational method for analysis of gunpowder residues was introduced into casework without changing the present operational technique for gunshot (primer) residue (GSR) analysis on clothing implemented by the Israel Police. In the modified method, the clothing is first sampled by double-side adhesive-coated aluminum stubs (the tape-lift method) for GSR analysis (the existing method), followed by vacuum collection for propellant residue examination. The issue of interpretation of the analytical results is discussed.

Recent developments in methods of chemical analysis in investigations of firearm-related events.

A review of recent (approximately the last ten years) developments in the methods used for chemical analysis in investigations of firearm-related events is provided. This review discusses:examination of gunshot (primer) residues (GSR) and gunpowder (propellant) residues on suspects and their clothing;detection of firearm imprints on the hands of suspects;identification of the bullet entry holes and estimation of shooting distance;linking weapons and/or fired ammunition to the gunshot entries, and estimation of the time since discharge.

Recent developments in the methods of estimating shooting distance.

A review of developments during the past 10 years in the methods of estimating shooting distance is provided. This review discusses the examination of clothing targets, cadavers, and exhibits that cannot be processed in the laboratory. The methods include visual/microscopic examinations, color tests, and instrumental analysis of the gunshot residue deposits around the bullet entrance holes. The review does not cover shooting distance estimation from shotguns that fired pellet loads.