Browsing by Author "Lewis, Simon W."
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Item 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 ScienceMicrospectrophotometry 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.Item 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 ScienceThe 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.Item Preparation, characterization, and application of a lipophilic coated exfoliated Egyptian blue for near-infrared luminescent latent fingermark detection(Forensic Chemistry, 2020-05-01) Shahbazi, Sorour; Goodpaster, John V.; Smith, Gregory D.; Becker, Thomas; Lewis, Simon W.A simple technique is described to create nanoscale near-infrared luminescent Egyptian blue pigment particles with lipophilic surfaces for latent fingermark detection. An exfoliated Egyptian blue powder coated with cetrimonium bromide was prepared using a simple, one-pot process. Particle size and surface coatings were characterized using scanning electron and atomic force microscopies, dynamic light scattering, and infrared and luminescence spectroscopies. This new fingermark dusting powder presents more contrast compared to uncoated Egyptian blue of comparable particle size as well as a commercial visible light fluorescent (Blitz Red) powder in the detection of aged fingermarks on model surfaces. The coated Egyptian blue pigment is a cost-effective fingermark dusting powder that reveals high contrast latent fingermarks with simple, inexpensive photography equipment.Item Studies into Exfoliation and Coating of Egyptian Blue for Application to the Detection of Latent Fingermarks(Chem Rxiv, 2020-09-23) Shahbazi, Sorour; Goodpaster, John V.; Smith, Gregory; Becker, Thomas; Lewis, Simon W.We have recently demonstrated that exfoliated Egyptian blue powder coated with cetrimonium bromide is effective for detecting latent fingermarks on a range of highly-patterned non-porous surfaces (see reference). In this extension of that work, we here present our preliminary studies into alternative approaches to preparing exfoliated Egyptian blue with a variety of different coatings. The various powders were then applied to the detection of latent fingermarks on non-porous surfaces. This proof of concept study demonstrated that there is potential improvement in performance compared to our previous work, however more comprehensive studies are required to compare the quality of the fingermarks developed with these powders against particles exfoliated in water.Item Studies into exfoliation and coating of Egyptian blue in methanol for application to the detection of latent fingermarks(Elsevier, 2022-07) Shahbazi, Sorour; Goodpaster, John V.; Smith, Gregory D.; Becker, Thomas; Lewis, Simon W.; Chemistry and Chemical Biology, School of ScienceWe have recently demonstrated that coated exfoliated Egyptian blue powder is effective for detecting latent fingermarks on a range of highly-patterned non-porous and semi-porous surfaces. In this extension of that work, we present our studies into an alternative approach to prepare exfoliated Egyptian blue coated with cetrimonium bromide and Tween® 20 using a simpler technique. The quality of the latent fingermarks developed with these exfoliated powders and the commercial powder were compared in a comprehensive study. Depletion series of natural fingermarks from a wide range of donors (12 males and females) deposited on non-porous (glass slides) and semi-porous (Australian banknotes) surfaces were used in this study. Enhancement in the performance of the coated exfoliated particles compared to the commercial powder was observed, particularly in the case of aged fingermarks and polymer banknotes as challenging substrates.