Data interpretation in forensic sediment and soil geochemistry

Automated geochemical techniques enable reproducible elemental assays of small quantity samples and have been used in recent years in many forensic criminal investigations in England and Wales. Two case studies are presented that highlight the problems of testing the presence of pre-, syn-, or post-crime event sample mixing. The number of elements or compounds analyzed can have a bearing on statistical discriminant techniques that may provide false-positive or false-negative associations or exclusions. Chemical analyses of soils and sediments using both atomic absorption spectrometry and Dionex (DX500 Sunnyvale, CA, USA), and inductively coupled plasma mass spectrometry enabled the identification and classification of discrete groups by hierarchical cluster analysis and canonical discriminant function analysis. These groupings, however, prove fragile to small variations within samples of even the most common minerals. Copyright © Taylor & Francis Group, LLC

The use of grain size distribution analysis of sediments and soils in forensic enquiry

The use of grain size distribution analysis in forensic enquiry was investigated with reference to four forensic case studies which contained the type of sample restraints and limitations often encountered in criminal case work. The problems of the comparison of trace and bulk samples are outlined and the need for multiple sample analysis is highlighted. It was found that the problems of soil analysis, particularly when the soil was recovered from anthropogenic sources, focused on the lack of identification of pre-, syn- and post-forensic event mixing of materials, thus obscuring the recognition of false-negative or false-positive exclusions between samples. It was found that grain size distribution analysis was a useful descriptive tool but it was concluded that if it were to be used in any other manner the derived results should be treated with great caution. The statistical analyses of these data did not improve the quality of the interpretation of the results

The philosophy, nature and practice of forensic sediment analysis

The rapidly expanding field of forensic geoscience derives its roots from nineteenth-and early twentieth-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 inaccurate 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 'mixing' is prerequisite to the application of statistical tests which must be applied in the most careful manner. The realization of the limitations of the technique requires, wherever possible, conjunctive analysis by other truly independent techniques. While 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. © 2007 SAGE Publications

The forensic analysis of soils and sediment taken from the cast of a footprint

The routine production of a cast of a shoe-print taken in soil provides information other than shoe size and gait. Material adhering to the surface of the cast represents the preservation of the moment of footprint impression. The analysis of the interface between the cast and soil is therefore a potentially lucrative source of information for forensic reconstruction. These principles are demonstrated with reference to a murder case which took place in the English Midlands. The cast of a footprint provided evidence of a two-way transfer of material between the sole of a boot and the soil of a recently ploughed field. Lumps of soil, which had dried on a boot, were deposited on the field as the footprints were made. Pollen analysis of these lumps of soil indicated that the perpetrator of the imprint had been standing recently in a nearby stream. Fibre analysis together with physical and chemical characteristics of the soil suggested a provenance for contamination of this mud prior to deposition of the footprint. Carbon/nitrogen ratios of the water taken from the cast showed that distilled water had been used thus excluding the possibility of contamination of the boot–soil interface. It was possible to reconstruct three phases of previous activity of the wearer of the boot prior to leaving the footprint in the field after the murder had taken place. This analysis shows the power of integrating different independent techniques in the analysis of hitherto unrecognised forensic materials

Conceptualising forensic science and forensic reconstruction. Part II: The critical interaction between research, policy/law and practice

This paper builds on the FoRTE conceptual model presented in part I to address the forms of knowledge that are integral to the four components of the model. Articulating the different forms of knowledge within effective forensic reconstructions is valuable. It enables a nuanced approach to the development and use of evidence bases to underpin decision-making at every stage of a forensic reconstruction by enabling transparency in the reporting of inferences. It also enables appropriate methods to be developed to ensure quality and validity. It is recognised that the domains of practice, research, and policy/law intersect to form the nexus where forensic science is situated. Each domain has a distinctive infrastructure that influences the production and application of different forms of knowledge in forensic science. The channels that can enable the interaction between these domains, enhance the impact of research in theory and practice, increase access to research findings, and support quality are presented. The particular strengths within the different domains to deliver problem solving forensic reconstructions are thereby identified and articulated. It is argued that a conceptual understanding of forensic reconstruction that draws on the full range of both explicit and tacit forms of knowledge, and incorporates the strengths of the different domains pertinent to forensic science, offers a pathway to harness the full value of trace evidence for context sensitive, problem-solving forensic applications

Conceptualising forensic science and forensic reconstruction. Part I: A conceptual model

There has been a call for forensic science to actively return to the approach of scientific endeavour. The importance of incorporating an awareness of the requirements of the law in its broadest sense, and embedding research into both practice and policy within forensic science, is arguably critical to achieving such an endeavour. This paper presents a conceptual model (FoRTE) that outlines the holistic nature of trace evidence in the ‘endeavour’ of forensic reconstruction. This model offers insights into the different components intrinsic to transparent, reproducible and robust reconstructions in forensic science. The importance of situating evidence within the whole forensic science process (from crime scene to court), of developing evidence bases to underpin each stage, of frameworks that offer insights to the interaction of different lines of evidence, and the role of expertise in decision making are presented and their interactions identified. It is argued that such a conceptual model has value in identifying the future steps for harnessing the value of trace evidence in forensic reconstruction. It also highlights that there is a need to develop a nuanced approach to reconstructions that incorporates both empirical evidence bases and expertise. A conceptual understanding has the potential to ensure that the endeavour of forensic reconstruction has its roots in ‘problem-solving’ science, and can offer transparency and clarity in the conclusions and inferences drawn from trace evidence, thereby enabling the value of trace evidence to be realised in investigations and the courts

The role of forensic geoscience in wildlife crime detection

The increase in both automation and precision in the analysis of geological materials has had significant impact upon forensic investigations in the last 10 years. There is however, a fundamental philosophical difference between forensic and geological enquiry. This paper presents the results of forensic geoscientific investigations of three cases of wildlife crime. Two cases involve the analysis of soils recovered after incidents of illegal badger baiting in the United Kingdom. The third case involves the illegal importation of Eleonora's Falcon (Falco eleonorae) into the United Kingdom from the Mediterranean. All three cases utilise the analysis of soils by a variety of physical, chemical and biological techniques. These involve mineral and grain size analyses, cation and anion compositions, pH, organic content and pollen analysis.The independent analysis undertaken by specialists in each of these three main fields conclude firstly, that there is a significant similarity between sediments taken at the crime site at both badger setts and with sediments recovered from various spades, shovels and clothing belonging to suspects and secondly, that the soils analysed associated with the removal of the falcon eggs in the Mediterranean contained characteristics similar in many respects to the soils of the breeding areas of E eleonorae on the cliffs of Mallorca. The use of these independent techniques in wildlife crime detection has great potential given the ubiquitous nature of soils and sediments found in association with wildlife sites. (c) 2006 Elsevier Ireland Ltd. All rights reserved

Forensic science. The importance of identity in theory and practice

There is growing consensus that there is a crisis in forensic science at the global scale. Whilst restricted resources are clearly part of the root causes of the crisis, a contested identity of forensic science is also a significant factor. A consensus is needed on the identity of forensic science that encompasses what forensic science ‘is’, and critically, what it is ‘for’. A consistent and cogent identity that is developed collaboratively and accepted across the entire justice system is critical for establishing the different attributes of the crisis and being able to articulate effective solutions. The degree to which forensic science is considered to be a coherent, interdisciplinary yet unified discipline will determine how forensic science develops, the challenges it is able to address, and how successful it will be in overcoming the current crisis