Abstract
Soil is a highly transferable source of trace physical material that is both persistent in the environment and varied in composition. This inherent variability can provide useful information to determine the geographical origin of a questioned sample or when comparing and excluding samples, since the composition of soil is dependent on geographical factors such as climate, bedrock geology and land use. Previous studies have limited forensic relevance due to the requirement for large sample amounts and unrealistic differences between the land use and geographical location of the sample sites. In addition the philosophical differences between the disciplines of earth sciences, for which most analytical techniques have been designed, and forensic sciences, particularly with regard to sample preparation and data interpretation have not been fully considered. This study presents an enhanced technique for the analysis of organic components of geoforensic samples by improving the sample preparation and data analysis strategies used in previous research into the analysis of soil samples by high performance liquid chromatography (HPLC). This study provides two alternative sets of marker peaks to generate HPLC profiles which allow both easy visual comparison of samples and the correct assignment of 100% of the samples to their location of origin when discriminating between locations of interest in multivariate statistical analyses. This technique thereby offers an independent form of analysis that is complementary to inorganic geoforensic techniques and offers an easily accessible method for discriminating between close proximity forensically relevant locations.
Highlights
Forensic geoscience is the scientific discipline that applies the techniques developed to study earth materials pertaining to the law and has applications in any legal context where earth materials may be able to help investigators, judges or jurors establish “what happened, where and when it occurred and how and why it took place” [1]
All four locations within Brockwell Park, London could be distinguished by the profiles of high performance liquid chromatography (HPLC) peak set A (Fig. 5)
It was not possible to discern any commonalities between similar location types at the different sites, for instance woodland soils were not shown to share similar profiles across all four parks, nor were any specific land use markers identified, suggesting that at this stage the HPLC technique is not yet able to provide intelligence related to the land use of the provenance location of an unknown sample
Summary
Forensic geoscience is the scientific discipline that applies the techniques developed to study earth materials pertaining to the law and has applications in any legal context where earth materials may be able to help investigators, judges or jurors establish “what happened, where and when it occurred and how and why it took place” [1]. Trace geoforensic materials recovered from a suspect, victim or crime scene can be analysed and interpreted in order to establish whether it is possible to discriminate between items or locations of forensic interest. The techniques used to do this are well established methods, developed in the earth science disciplines for the purpose of studying the geographical and geological phenomena, which have been retrospectively adapted to forensic work and typically test the physico-chemical characteristics of the inorganic fraction of geoforensic samples [3,4,5]. There are clear differences, both from a conceptual and pragmatic point of view, for instance in the sample size and the level of spatial and temporal precision required, between the problems and questions encountered in forensic casework and those encountered in earth science research, careful consideration must be given to these philosophical differences in order to properly interpret the data generated by these techniques. There is significant value in the development of analytical methods that incorporate the specific requirements of forensic casework [6,7,8,9,10,11]
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