Applications of Chemometrics to the Analysis and Interpretation of Forensic Physical Evidence

Faculty of Science and Engineering Department of Chemistry Applications of Chemometrics to the Analysis and Interpretation of Forensic Physical Evidence Georgina Yasmin Sauzier This thesis is presented for the Degree of Doctor of Philosophy of Curtin University July 2016 Declaration To the best of my knowledge and belief, this thesis contains no material previously published by any other person except where due acknowledgement has been made. This thesis contains no material which has been accepted for the award of any other degree or diploma in any university. Signature: Date: 13/07/2016 Page | i Abstract Forensic investigations often depend upon the recovery and analysis of physical evidence to reconstruct the events surrounding a crime. Though consensus standards have been established in this regard, these typically rely on the interpretation of complex data by an examiner, leading to apprehensions regarding human error or bias. Additionally, there are limited rigorous studies concerning the appropriate handling of forensic exhibits to maximise their evidential value. Recent decades have therefore seen an increased interest in developing more objective methods for assessing evidentiary significance, as well as statistically validated sampling and handling procedures. This may be achieved by employing multivariate statistics, or chemometrics, to provide objective measures of analytical data using well-established statistical protocols. This dissertation describes a series of investigations applying chemometrics to various aspects of forensic physical evidence examination, with a specific focus on textile fibres, writing inks and explosive residues. Microspectrophotometry (MSP) and chemometric pattern recognition were first used to conduct simulated “questioned versus known” comparisons on several blue-dyed acrylic fibre sets. Fisher’s Exact test was applied to the resultant data, providing a quantitative measure of sample similarity or dissimilarity. The majority of fibre sets formed distinct groupings on the basis of their overall dye composition, giving a true exclusion in 108 of 110 comparisons. Comparison of fibres within the same set resulted in a true inclusion in 10 out of 11 scenarios, with the one false exclusion attributed to a lack of spectral reproducibility. This methodology, whilst not infallible, could thus provide a more objective and statistical basis on which forensic examiners can support their conclusions in court. Chemometrics with diffuse reflectance visible spectroscopy was then investigated as an in situ characterisation method for inks on paper. Analysis of spectra from 35 blue ballpoint inks found several to be clearly distinguishable, though others exhibited overlap. A subsequent discriminant model resulted in 88.4 % of spectra being correctly assigned to the source pen or supplier. This model could be used to generate probative information from a questioned document, or could alternatively be utilised as a rapid, non-destructive screening method for document examination. Page | ii Analysis of six ballpoint inks stored under various office conditions found that they remained chemically stable for at least 14 months in the dark. Conversely, inks exposed to light could exhibit spectral changes within just one week, resulting in altered predictions using the chemometric model. This could prove beneficial when attempting to detect alterations made to a document using the same pen as the original entry at a later date. Multivariate calibration was employed in an attempt to model these changes for ink dating purposes, but the estimations afforded by these models proved unreliable. Artificial ageing experiments found that both heat and ultraviolet light play a role in the ageing process, and that accelerated ageing using these factors gives a reasonable depiction of short-term ageing under natural conditions. Further work in this area employed a video spectral comparator (VSC) as a means of obtaining visible spectra from handwritten ink entries, rather than the larger deposits employed previously. The VSC was found to give lower specificity between similar inks, with a classification accuracy of only 31.7 % achieved using an independent test set. Discriminant models based upon chromaticity values or fluorescence spectra were similarly unsuccessful. Fluorescence was then utilised as an initial binary classifier. Chemometric analysis was conducted on the visible spectra of fluorescent and non- fluorescent inks, giving improved separation. Further specificity could be achieved by categorising the fluorescent inks according to their observed fluorescence intensity. However, as this was done based on personal opinion, a level of human bias could be introduced to the results. Finally, experimental design was utilised with gas chromatography-mass spectrometry (GC-MS) to determine optimum sampling, storage and extraction procedures for the recovery of smokeless powder residues from steel surfaces. The optimised protocols were successfully applied to post-blast residues deposited on steel witness plates through detonation of a pipe bomb device, with a rate of detection exceeding 95 % for both nitroglycerin and diphenylamine. These results provide a high level of confidence that explosive events involving smokeless powder formulations will be readily identified using the suggested parameters. The methodology employed here may also be readily applied to a variety of other explosive compounds, and thus assist in establishing ‘best practice’ procedures for explosive investigations. Page | iii Acknowledgements I would like to acknowledge the many, many people who have made this project possible – and, on occasion, even fun. First and foremost, I must thank Professor Simon Lewis for his guidance and encouragement (however dubious) throughout this research. He deserves no small measure of respect for having tolerated me this long. Secondly, to Emeritus Professor Bill van Bronswijk for bestowing wise counsel, reviewing my manuscripts with only as much red ink as strictly necessary, and occasionally reminding me not to take things too seriously. I am also indebted to Associate Professor John Goodpaster at Indiana University-Purdue University, Indianapolis (IUPUI), for hosting me in his laboratory and providing me use of his vast expertise on trace evidence and chemometrics. I will forgive you for making me do all of those fibre statistics if you forgive me for using all of your SPME vials (twice). I would like to acknowledge Dr Stephen Morgan (University of South Carolina) for the provision of fibre samples, as well as Eric Reichard, Dana Bors, Wil Kranz and Marie Diez (IUPUI) for obtaining the MSP spectra. Additionally, thanks are due to both Dana and Jordan Ash (IUPUI) for their assistance with the explosives studies, and for not complaining about me hogging their GC. I would like to extend appreciation to the Indianapolis PD Bomb Squad (specifically Sergeant Leonard Langland and Officer Benjamin Cook) and the city of Martinsville, Indianapolis for facilitating the pipe bomb trial – without which this research project would have been considerably less interesting. I must also acknowledge the various students at IUPUI who assisted in the tedious preparation of witness plates or collection of post-blast samples. Thanks also to Geoff Day (Australian Federal Police) and Jasmina Clyburn (U.S. Bomb Data Centre) for providing statistics regarding reported explosive incidents, such that this work could be placed within the appropriate context. Page | iv I must thank John Coumbaros for allowing me to access the instrumentation at ChemCentre, as well as Rees Powell for providing training in Raman spectroscopy. Likewise, many thanks to Tonya Trubshoe and John McGinn (Document Examination Solutions, WA) for allowing me to regularly troop in and out of their office to use their VSC. I would like to acknowledge Peter Giles for conducting initial proof-of-concept tests regarding ink analysis, and Peter Chapman for his assistance with visible spectroscopy (as well as keeping me on my toes). On a personal note, much gratitude is due to Jay Siegel and Maggie Wilke for being the best hosts (and tour guides) I could have asked for. My time in Indianapolis would not have been nearly as enjoyable without them. I must also thank the ‘Goodpaster Group’ at IUPUI for helping me find my feet, saving the GC (and subsequently a large portion of my project), and introducing me to such wonders as Marco’s Pizza buffet. Your collective craziness truly made me feel at home. On that subject, I must also thank the Curtin Forensic & Analytical Chemistry Research Group for making this journey much more entertaining than I would have imagined. Our numerable shenanigans will serve to remind me that work and play are equally important, and that it’s sometimes easier to ask forgiveness than permission. I am also grateful to all of my friends, both in university and out, for giving me the occasional break from my PhD and only asking “are you done yet?” every few months or so. Last but by no means least; I would like to thank my family and Allan for their everlasting support. They might not have understood anything I’ve been doing for the past three and a half years, but even when I had my doubts, they have always believed that I would make it. Page | v Publications This dissertation contains work which has been submitted for publication in the following peer reviewed journals: G. Sauzier, P. Giles, S.W. Lewis and W. van Bronswijk. In situ studies into the

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