Methods for analysis of glass in glass-containing gunshot residue (gGSR) particles

© 2019 Elsevier B.V. This manuscript version is made available under the CC-BY-NC-ND 4.0 license: http://creativecommons.org/licenses/by-nc-nd/4.0/ This author accepted manuscript is made available following 12 month embargo from date of publication (March 2019) in accordance with the publisher’s archiving policyWhen lead, barium and antimony, or lead, barium, calcium, silicon and tin are found together in particles associated with a shooting investigation they are considered characteristic of gunshot residue (GSR). Antimony and tin are often absent from the primer of many low calibre rimfire ammunitions, which are the type most commonly used in Australia. Therefore, the likelihood of characteristic particles forming during the firing process of such rimfire ammunition is significantly less than the likelihood of these particles arising from higher calibre ammunition. The majority of rimfire ammunition examined in this research contains ground glass in the primer, which functions as a frictionator. These ammunitions produce a small number of gunshot residue particles containing glass coated with other primer components, which we refer to as glass-containing GSR (gGSR). If these particles are observed in an investigation, they have the potential to add a new dimension to gunshot residue analysis because they are not common in the environment. Furthermore, the composition of glass frictionator is stable during firing, which raises the possibility that chemical testing of the glass in gGSR may be used to identify the ammunition from which the residue was derived or to link deposits of GSR. This paper examines the application of scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDS), focussed ion beam (FIB) techniques and time of flight-secondary ion mass spectrometry (ToF-SIMS) to the semi-quantitative analysis and comparisons of gGSR and frictionator extracted from unfired cartridges. SEM-EDS is effective for comparing gGSR with unfired frictionator, but the use of FIB to expose clean glass from the centre of gGSR followed by ToF-SIMS, or ToF-SIMS using ion sputtering to expose clean glass, offers more power for comparisons due to their capability for higher discrimination between frictionators from different sources

Evaluation of the sub-surface morphology and composition of gunshot residue using focussed ion beam analysis

© 2019 Elsevier B.V. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ This author accepted manuscript is made available following 12 month embargo from date of publication (January 2019) in accordance with the publisher’s archiving policyRecent work in the forensic analysis of Gunshot residues (GSR) has suggested that the sub-surface or internal composition and morphology of these residues be explored. A particular area of interest is in heavy metal free, or non-toxic ammunition, which are becoming more frequently encountered in the marketplace. As the formulation of the primer compound changes the conditions of the firearm discharge, there is the possibility that different primer formulations may result in the formation of different GSR particles with distinct internal morphologies and compositions. To that end, the internal morphology and composition of GSR particles may provide additional information that could be useful in the investigation of firearms crime. This research investigated the internal morphology of GSR originating from a variety of different ammunition products. Both traditional three-component primed ammunition, and a selection of heavy metal free and non-toxic alternatives were considered. Particles were identified using SEM–EDS, before being cross-sectioned using a focussed ion beam (FIB) instrument. The FIB-sectioned particles were then re-acquired and mapped using SEM–EDS, to assess both internal morphology and composition. Particles observed in this study presented distinct morphological and compositional features at the sub-particle level that may provide an indication of the primer formulation from which they originated. That said, further investigation of a variety of samples should be undertaken to verify the consistency of these features, or any deviations that may be observed based on primer type. However, these results indicate that there may be promise in obtaining additional detail from sub-particle morphology and composition