Development of ion beam analysis methods for the characterisation of gunshot residue

• Main Author: Christopher, Matthew E.
• Published: University of Surrey 2012
• Subjects: 363.259
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.581802

This thesis investigates the feasibility of using ion beam analysis (IBA) techniques for the characterisation of gunshot residue (GSR) in forensic casework. GSR-is an important type of trace evidence used to link suspects to shooting incidents. The current forensic procedure for GSR analysis utilises scanning electron microscopy with energy dispersive X -ray spectroscopy (SEM-EDS), but this lacks sensitivity to important trace elements when compared with IBA. In this thesis, the development of a new protocol for GSR analysis by IBA is described, including a robust particle relocation method, an efficient spectral fitting process and the implementation of a background subtraction procedure. Canonical discriminant function analysis (CDP A) is employed to demonstrate the ability of IBA to discriminate between different brands of ammunition in a way not currently possible using existing GSR casework methodologies. A database of results for GSR particles collected from cartridge cases and hands is presented along with a discussion as to how it would be best utilised in a casework scenario. An investigation into how IBA can be applied to lead-free ammunitions is also presented. These ammunitions are known to produce particles that are problematic for forensic examiners to positively identify as being GSR. IBA is shown to increase the evidential value of such particles due to the higher sensitivity of IBA when compared with SEM-EDS. IBA is shown to offer improved discrimination between all types of ammunition using methods that would not require any alteration to well- established sample collection and preparation procedures.