Scott, KR; (2017) The application of freshwater diatom analysis in forensic geoscience: establishing an empirical evidence base for the exclusionary assessment of trace environmental materials. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Diatoms contribute valuable geoforensic trace evidence indicators due to their natural abundance, species diversity, and tenacity in various environments pertinent to forensic enquiry including freshwater, marine, and terrestrial sites. Although the exclusionary assessment of freshwater diatoms has been demonstrated in forensic casework, relatively little empirical research is currently documented within the field. This thesis addresses this research gap through the development of a systematic study, accounting for the spatial and temporal dynamics of diatom traces at different stages of the forensic investigation process. A series of experiments were performed to examine the pre-investigation transfer and persistence of freshwater diatoms on different clothing surfaces, and to develop the techniques and approaches available for the collection and analysis of evidential material. Additionally, two mock crime scenarios were designed to apply the empirical findings in casework contexts and to identify potential limitations during the exclusionary interpretation of evidence. A total of 1,236 diatom samples were collected and analysed using light (x1000 magnification) and scanning electron microscopy (SEM). The findings demonstrated that seasonality, the background prevalence of diatoms, clothing material characteristics, the site of initial contact (planktonic/benthic habitats), and diatom particulate morphology/ornamentation, all impact upon the total number of diatoms and the species diversity of an assemblage transferred and retained upon clothing over time. In addition, four new approaches for the rapid, comprehensive, and non-destructive collection and analysis of diatoms and other freshwater trace indicators adhered to clothing were also defined. This research presents the first systematic empirical assessment of freshwater diatom analysis for forensic reconstruction, and contributes important data to the evidence bases required to support forensic practice and underpin the exclusionary interpretation of diatom trace evidence in court. Furthermore, the findings from this research offer recommendations to inform, support, and extend the current applications of diatom analysis in forensic casework.

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