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Unusual sources of Sn in GSR. An experimental study by SEM and IBA

Romolo, Francesco Saverio, Bailey, Melanie J., De Jesus, Janella, Manna, Luigi and Donghi, Matteo (2019) Unusual sources of Sn in GSR. An experimental study by SEM and IBA Science & Justice, 59 (2). pp. 181-189.

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Abstract

Gunshot Residue (GSR) produced by the discharge of a firearm often provides very useful information in criminal investigations in cases involving the use of firearms. Scanning Electron Microscopy equipped with an Energy Dispersive X-ray Spectrometer (SEM-EDS) is typically used worldwide to visualize micrometric particles constituting GSR and to analyse their elemental composition. The 2017 ASTM Standard guide for gunshot residue analysis by scanning electron microscopy/energy dispersive X-ray spectroscopy specifies that “Particles classified as characteristic of GSR will have one of the following elemental compositions: Lead, antimony, barium; Lead, barium, calcium, silicon, tin”. For the first time, the presence of an additional element, such as Sn, plays a key role in ASTM particle classification. It is known that some ammunitions, used for pistols, revolvers and rifles, contain tin foil discs for sealing the primer mixture into the cup, resulting in GSR particles containing Sn. The authors faced some cases in which Sn was unexpectedly found in GSR particles from a 0.22 Long Rifle derringer and from some 12 gauge shotguns. No tin foil discs are used in rimfire ammunitions and there is no published evidence of tin foil discs in shotshell ammunitions. Following a “case by case” approach, experimental research has been carried out to explain how Sn can be present in GSR particles when the last discharged cartridge also does not contain any Sn either in components and in the explosive charges.

Moreover, the use of Particle Induced X-ray Emission (PIXE) showed the capability to overcome overlap ambiguity of Sb and Sn peaks in the X-ray spectra, being a possible key issue in real shooting cases if Sn quantities are below the lower limit of SEM detection, especially when Sb is also present.

Item Type: Article
Divisions : Faculty of Engineering and Physical Sciences > Chemistry
Authors :
NameEmailORCID
Romolo, Francesco Saverio
Bailey, Melanie J.M.Bailey@surrey.ac.uk
De Jesus, Janellaj.dejesus@surrey.ac.uk
Manna, Luigi
Donghi, Matteo
Date : March 2019
Funders : Engineering and Physical Sciences Research Council (EPSRC)
DOI : 10.1016/j.scijus.2018.10.009
Copyright Disclaimer : © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
Uncontrolled Keywords : Gunshot Residue (GSR); Firearms Discharge Residue (FDR); Scanning Electron Microscope (SEM); Ion Beam Analysis (IBA); Tin
Depositing User : Clive Harris
Date Deposited : 30 Jan 2019 15:01
Last Modified : 26 Jul 2019 07:32
URI: http://epubs.surrey.ac.uk/id/eprint/850324

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