This review paper covers the forensic-relevant literature in gunshot residue analysis from 2016 to 2019 as a part of the 19th Interpol International Forensic Science Managers Symposium. The review ...papers are also available at the Interpol website at: https://www.interpol.int/content/download/14458/file/Interpol%20Review%20Papers%202019.pdf.
In shooting incident investigations where it is important to estimate the shooting distance, the sodium‐rhodizonate coloring method has been used for the visualization of GSR patterns extensively. ...This publication describes the optimization of this method by the use of a heated press for the transfer of GSR traces on garments, as well as variation of a number of other important process parameters. Our final aim for this project was to prepare a formal validation of the coloring method as prerequisite for its inclusion into the scope of ISO17025‐certified methods in the GSR Laboratory. A number of important factors and process parameters were identified, such as buffer composition and pH, type of textile used as a substrate and resolution of the documentation of the results. Results were tested using a synthetic proficiency test. Our optimized method has been found to be a very effective technique for visualization of macroscopic GSR traces.
Abstract The presence of gunshot residues (GSRs) on arrested suspects can help the Court to form an opinion regarding the possibility of utilization of firearms by these suspects. Since the presence ...of a few particles can in some cases already have a strong indicative value, the GSR experts have to evaluate in their daily work the risk of a potential contamination of these suspects during their arrest. A few studies conducted on police officers and police facilities concluded that the risk of secondary transfer on arrested suspects is quite negligible. However, the case of special force units of the police should be taken into account, since these units can be assumed to be highly contaminated by GSR due to their intensive training. The aim of this study is to evaluate this possibility of particle transfer by performing simulations of arrests by special force police units, according to both low and high contamination scenarios. The results show that secondary transfers of GSR during these simulations are in most cases not negligible, even for the low contamination scenario. This is especially apparent on the vests of the target persons, with an average of 7 GSR particles (2 PbBaSb and 5 TiZn) found on the stubs used on these materials. Of course, the major contamination levels were observed in the case of the high contamination scenario, due to the use of highly contaminated gloves by the police officers during the arrests. Some recommendations are proposed to take into account this risk of contamination and to try to minimize it, or at least to better identify it.
Abstract Collection efficiency of gunshot residues (GSR) as a function of the type of fabric was evaluated. For this set of experiments, fabrics with differences in their sheddability were exposed to ...shootings. The samples were then stubbed to collect GSR following a standard procedure for SEM/EDX analysis. The results show a strong relationship between sheddability and collection efficiency, since the collection efficiency is about five-fold higher for leather compared with wool. The main factor explaining this difference is probably the rate of saturation (for instance by fibres) of the carbon tapes used to stub the fabrics. An example originating from a real case supports this hypothesis.
Abstract Since 2008, our laboratory has adopted a systematic approach to the examination of gunshot residues (GSR) in casework by analysing, whenever possible, the inorganic composition present in ...ammunition (cartridge cases and unused ammunition). By compiling the results of these analyses in a database, it is possible to observe some trends during the period of interest: on the one hand, the prevalence of primers containing lead, barium and antimony is about 50%, and even as high as 70% when including lead–barium–antimony based primers also containing tin; on the other hand, the prevalence of non-toxic primers is for the time being very low. Still using the same approach, test firings were performed with recovered weapons and litigious ammunition whenever possible in order to estimate the influence of the well known “memory effect” of the weapons on the GSR analysis results. The first results show a quite strong memory effect for the .22 and the .32 caliber, unlike the .38 caliber. This is probably due to a high prevalence of lead–barium–antimony based primers for the latter caliber.
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