Browsing by Author "Sauzier, Georgina"

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    Improving the confidence of “questioned versus known” fiber comparisons using microspectrophotometry and chemometrics
    (Elsevier, 2016-11) Sauzier, Georgina; Reichard, Eric; van Bronswijk, Wilhelm; Lewis, Simon W.; Goodpaster, John V.; Department of Chemistry and Chemical Biology, School of Science
    Microspectrophotometry followed by chemometric data analysis was conducted on pairs of visually similar blue acrylic fibers, simulating the “questioned versus known” scenarios often encountered in forensic casework. The relative similarity or dissimilarity of each pair was determined by employing principal component analysis, discriminant analysis and Fisher’s exact test. Comparison of fibers from within each set resulted in a correct inclusion result in 10 out of 11 scenarios, with the one false exclusion attributed to a lack of reproducibility in the spectra. Comparison of fibers from different sets resulted in a correct exclusion result in 108 of 110 scenarios, with two sets that shared identical dye combinations being indistinguishable. Although the presented methods are not infallible, they may nonetheless provide a path forward for forensic fiber examiners that has a more scientifically rigorous basis on which to support their findings in a court of law.
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    Optimisation of recovery protocols for double-base smokeless powder residues analysed by total vaporisation (TV) SPME/GC-MS
    (Elsevier, 2016-09) Sauzier, Georgina; Bors, Dana; Ash, Jordan; Goodpaster, John V.; Lewis, Simon W.; Chemistry and Chemical Biology, School of Science
    The investigation of explosive events requires appropriate evidential protocols to recover and preserve residues from the scene. In this study, a central composite design was used to determine statistically validated optimum recovery parameters for double-base smokeless powder residues on steel, analysed using total vaporisation (TV) SPME/GC-MS. It was found that maximum recovery was obtained using isopropanol-wetted swabs stored under refrigerated conditions, then extracted for 15 min into acetone on the same day as sample collection. These parameters were applied to the recovery of post-blast residues deposited on steel witness surfaces following a PVC pipe bomb detonation, resulting in detection of all target components across the majority of samples. Higher overall recoveries were obtained from plates facing the sides of the device, consistent with the point of first failure occurring in the pipe body as observed in previous studies. The methodology employed here may be readily applied to a variety of other explosive compounds, and thus assist in establishing ‘best practice’ procedures for explosive investigations.