The philosophy, nature and practice of forensic sediment analysis

Abstract

The rapidly expanding field of forensic geoscience derives its roots from 19 th and early 20 th Century scientists who both influence and are influenced by literature and fictional writing. Forensic geoscience borrows much, but not all, of its precepts from geological and geomorphological analytical techniques.Fundamental differences exist between forensic geoscience and its sister disciplines, fundamental enough to make the unwary geoscientist succumb to philosophical and practical pitfalls which will not only endanger the outline of their report, but may well indeed provide false-negative or false-positive results leading to contrary or wrongful conclusions. In the law, such outcomes have devastating and untenable consequences.Forensic geoscience requires techniques of exclusion rather than inclusion and an acknowledgement that analytical techniques may be diagnostic only in very specific situations. Whether analysis of the ubiquitous or the exotic component is chosen, acknowledgement of the need for samples to be representative is required.The presentation of false-positive results or the lack of identification of sample 'contamination' is prerequisite to the application of statistical tests which must be applied in the most careful manner. The realisation of the limitations of the technique requires, wherever possible, conjunctive analysis by other truly independent techniques. Whilst personal opinion derives from experience, there is no place for assumption. Research papers in forensic geoscience are not submitted to be speculative or challenging as may be the case in many fields of geomorphology and geology. There is no place for conjecture in forensic geoscience.

High Performance Liquid Chromatography as a valuable tool for geoforensic soil analysis

“…This offers potential for false positive or false negative results since components acquired before, during and after a forensic event can become mixed 16−18,24−26 . Furthermore, many existing techniques require sample quantities in excess of the materials recovered from items of forensic interest, such as shoes, clothing or vehicles 5,[20][21][22]24,26 . It is, therefore, valuable to develop analytical methods that take into account these specific requirements of forensic casework 27 .…”

“…The re-developed method was intended to be appropriate for comparing trace soil samples for the purposes of excluding crime scene, alibi site and unknown samples. These contextual details are important, since the priorities in civil or environmental forensic cases, those involving bulk samples and those that aim to predict the geographic provenance of a sample are significantly different, as are the considerations required for the robust interpretation of the evidence 5,19,27 . Therefore, this paper seeks to address whether it is possible to distinguish groups of trace soil samples obtained from locations that are located in close proximity to one another (and thus forensically relevant to a crime reconstruction) using HPLC analysis for forensic applications.…”

“…It is, of course, recommended that forensic evidence is tested with techniques that analyse independent characteristics of the sample in order to provide significance to the conclusions drawn 5,16,17 . To complement this study into the discriminatory value of the organic components of the soil, analysis of the inorganic fraction of the samples was also undertaken.…”

The relevance of the evolution of experimental studies for the interpretation and evaluation of some trace physical evidence

“…By demonstrating that washed training shoes may retain geoforensic material and establishing which locations on and within the shoe are most likely to yield such evidence, it was possible to recover evidence from the shoes submitted for analysis in this case. It was possible to undertake a number of analytical tests on that trace evidence (mineralogy, colour, quartz grain surface texture analysis) with the result that it was not possible to exclude the sediment retained within the training shoes from having derived from the same provenance as the soil/sediment collected from the body deposition site and from within the vehicle (following the philosophical approach promoted by Walls [13] and later by Morgan and Bull [14]). The experimental work provided a context in which to couch the results of the analysis of the geoforensic material and again gave greater evidential weight to the findings.…”

Sediment fingerprints: A forensic technique using quartz sand grains — A response

“…It only attempts to exclude. This is the basic tenet of forensic geoscience that is so often ignored or overlooked by geoscientists [4][5][6][7]. Unfortunately some practitioners still attempt to match samples [8][9][10][11][12][13] and this classification system and database was not constructed to be used in this way.…”