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Forensic geoscience: introduction and overview

KENNETH PYE 1,2 & DEBRA J. CROFT 1,3

Kenneth Pye Associates Ltd, Crowthorne Enterprise Centre, Crowthorne Business Estate, Crowthorne RG45 6AW, UK (e-mail: [email protected]) 2 Department of , Royal Holloway, University of London, Egham Hill, Egham TW20 OEX, UK 3 Croft Scientific & Technical, Blaen-y-Waun, Llanafan, Ceredigion SY23 4BD, UK

The nature of forensic geoscience Contribution of geoscience to forensic investigations Forensic geoscience may be defined as a subdisci- pline of geoscience that is concerned with the appli- The potential contribution of studies of rocks, min- cation of geological and wider environmental erals and sediments to criminal investigations was science information and methods to investigations recognized more than a century ago by the American which may come before a court of law. The scien- criminologist Professor Hans Gross, and other early tific boundaries of forensic geoscience are not advocates in the early part of this century included clearly defined, and there are significant overlaps the German forensic scientist Georg Popp and the with other, related subdisciplines such as forensic French pioneer archaeology (Hunter et al. 1987), forensic anthro- (see Murray 2004). However, it was not until 1975 pology, forensic botany (Hall 2002; Horrocks & that the first textbook on forensic geology was pub- Walsh 1998), (Shuirman & lished (Murray & Tedrow 1975), and there is still Slosson 1992) and even forensic medicine and only a very limited dedicated literature in the field. (Knight 1997; DiMaio & Many general texts on investigation and DiMaio 2001). Forensic geoscience is concerned criminalistics make little or no mention of forensic with all aspects of materials, including rocks, geology or soil evidence (e.g. Fisher 2000; sediments, soil, air and water, and with a wide range Saferstein 2001), and there is widespread ignorance of natural phenomena and processes. Since modern among the legal profession and police forces about sediments and soil also often contain objects and its potential (e.g. White 1998; Townley & Ede 2004). particles of human origin, man-made materials such Even among forensic practitioners, there are still as brick, concrete, ceramics, glass and various other many who believe that 'soil is soil, sand is sand, and industrial products and raw materials are also some- mud is mud'. times of interest. These may be of relatively modern In actual fact, there is an enormous diversity origin or of archaeological importance (e.g. among earth surface materials, and the fact that Henderson 2002). modern techniques are capable of very detailed char- Forensic geology (Murray & Tedrow 1975, 1992) acterization and discrimination makes such material may be regarded as a subset of forensic geoscience potentially highly useful in a forensic context. and is principally concerned with studies of rocks, Forensic geoscience techniques and information can sediments, minerals, soils and dusts. Environmental be applied to a wide range of civil law and criminal forensics (Morrison 2000; Murphy & Morrison law issues, relating to such problems as environmen- 2002), on the other hand, has somewhat wider scope tal accidents, construction failures, pollution and, of than forensic geoscience, with much stronger links course, serious crimes such as murder, terrorism, to disciplines such as chemical engineering, and genocide, arson, drug smuggling and rape. with a greater concern with such issues as ground- Forensic geoscience information may be used water contamination and air pollution modelling. simply for 'intelligence' purposes within the frame- Forensic geoscience is by nature an integrative work of an ongoing police investigation or as evi- subdiscipline that draws directly on other subdisci- dence for presentation in court, depending on the plines in earth science such as , geochem- quality of data and strength of the conclusions which istry, , and can be drawn. By combining geological information geoarchaeology. These, in turn, draw on the funda- with data obtained from related subdisciplines, such mental sciences (physics, chemistry and biology) as forensic botany, useful information about prove- and other derivative disciplines such as engineering, nance and geographical location can be provided. medicine, archaeology and anthropology (Fig 1). This type of approach is sometimes referred to as 'environmental profiling' and is analogous to the

From: PYE, K. & CROFT, D. J. (eds) 2004. Forensic Geoscience: Principles, Techniques and Applications. Geological Society, London, Special Publications, 232, 1-5. 9 The Geological Societyof London, 2004. Downloaded from http://sp.lyellcollection.org/ by guest on September 27, 2021

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Fig. 1. The relationship of forensic geoscience to some other disciplines and subdisciplines.

geographical profiling and psychological profiling suspect, including footwear, clothing, digging undertaken by behavioural scientists. Geoscientists implements or car, are routinely examined for traces can also assist in tasks such as body location through of blood, DNA, fibres or hair that might link the the application of and other suspect to the victim or the scene, but increasingly remote-sensing techniques (Fenning & Donnelly they are also being examined for traces of soil, mud, 2004; Watters & Hunter 2004; Scott & Hunter dust or pollen that might also indicate a link. 2004). Increasing forensic awareness among criminals, In recent years, soil and geological evidence has many of whom now take precautions not to leave been increasingly used in investigations and both DNA or similar traces, means that new types of criminal and civil law trials in the UK, but world- potential evidence need to be found. wide its acceptance in the courts varies from country In such a case, the investigator may well be pre- to country. This partly reflects the different legal tra- sented initially with an exhibit such as that shown in ditions, the greatly varying degree of sophistication Figure 2, a pair of shoes with relatively small displayed in the investigation and analysis methods amounts of mud on the soles. In view of the rela- between different countries. However, professional tively small amount of material available for analy- and public awareness of the potential power of sis, the investigator needs to draw up an examination forensic geoscience evidence is increasing, and there and analysis strategy in order to maximize the can be little doubt that it will become increasingly amount of information that can be obtained from the used on a global scale over the coming decades. removed material and to obtain the maximum evi- dential value possible. This requires selection of the most appropriate analytical techniques, as well as Key questions and approaches the collection of appropriate background data against which the analytical data can be compared. In serious crime cases, one of the most common Two key questions are typically asked by investi- tasks is to determine whether a suspect (or his means gating police officers: (1) is there a 'match' between of transport, such as a car or motorcycle) was present the mud on the shoes and the crime scene, and, if so, at the scene of a crime. Items seized from the (2) what is the evidential value of such a 'match' ? In Downloaded from http://sp.lyellcollection.org/ by guest on September 27, 2021

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possible to say with virtual certainty that the crime scene was the source. This normally arises where there is some form of physical fit, for example between two halves of a broken , or where soil is taken from a characteristic shoe impression in the ground. It may also be possible where one or, more commonly, several, highly unusual particle types (sometimes referred to as 'exotics') are found in common between the questioned soil sample and the crime scene control samples. In many cases, however, no such evidence is available, and assess- ment of degree of match and its significance must be based on comparison of several different bulk sample properties, which are evaluated using a com- bination of statistical, graphical and other methods. Assessment of evidential value involves both quan- tification of the degree of similarity between two samples and comparison with data in some form of database which can provide information about similar samples in other locations. The quality of database information varies from place to place, and in many investigations it is necessary to collect and analyse additional samples for comparison purposes Fig. 2. Footwear with mud deposits on the soles specifically in the context of the investigation in belonging to a murder suspect, later convicted. Attempts hand. It goes without saying that the better the data- had been made to scrape mud off the sole of the shoe on base and quality of contextual information available, the right. the greater the confidence that can be placed in any conclusions reached. Contextual information order to address the first question the material must includes such factors as the timing of the alleged be examined and analysed in as lnany ways as possi- offence and seizure of the exhibit (e.g. footwear), ble, in order to determine whether any significant method of storage and nature of any previous exami- differences exist between the questioned sample and nations, and whether the suspect lived close to the the known samples taken from the crime scene, the crime scene or had any legitimate reason to visit it. initial objective being to establish whether the possi- Investigating officers have a duty to provide the bility can be excluded that the questioned sample investigator with as much relevant information as originated from the crime scene. The examination possible without deliberately trying to influence and analysis techniques used should be as non- acquisition or interpretation of the results. destructive as possible, both to maximize the poten- It is always advantageous if the forensic geoscien- tial for as many tests as possible to be carried out and tist has an opportunity to examine critical exhibits to preserve evidence for possible later defence first hand and to undertake any sampling of soil and examination. A wide range of techniques is available mud that may be necessary. In this way, the sequence (as discussed by Jarvis et al. 2004; Blott et al. 2004; of mud acquisition may be identified and appropriate Pye 2004a, b; Edwards 2004; and others in later types of samples collected for analysis. Scenes of chapters in this volume) and considerable experi- crime officers and police often are not fully aware of ence is required in order to assess which techniques the requirements for geological sample collection, are likely to provide the most significant information storage and handling, although the situation is in any particular situation. improving. Similarly, it is of great benefit if the If test results show that the questioned mud cannot forensic geoscientist is able to visit the crime scene, be excluded as having come from the crime scene, preferably as soon as possible after the crime has the next question is one of the degree of similarity, or been discovered. By doing so, hypotheses for inves- 'match', and its evidential significance. No two tigation are generated and suitable 'control' samples natural soil or sediment samples are ever absolutely can be taken. identical, and the key issue is therefore to decide The fact that geoscience, like all natural sciences, how much similarity, and how much dis-similarity is not an exact science does not undermine its useful- exists, and with what degree of probability it can be ness in a court of law. Geological and soil trace evi- stated that the questioned sample did originate, in dence is in many respects similar to glass and fibre whole or in part, from the crime scene. evidence, where probabilities of occurrence and sig- In some, relatively rare, circumstances it may be nificance of findings are best considered within a Downloaded from http://sp.lyellcollection.org/ by guest on September 27, 2021

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Bayesian type framework rather than solely through DIMA:O, V. J. & D~MAIo, D. 2001. Forensic Pathology. 2nd attempts to apply conventional statistics (Small et al. edition. CRC Press, Boca Raton. 2004). Inevitably, however, there will be situations EDWARDS, H. G. M. 2004. Forensic applications of Raman when it is not possible for the geoscientific expert spectroscopy to the non-destructive analysis of bio- materials and their degradation. In: PYE, K. & CROFT, witness to offer anything more than an expert D. J. (eds) Forensic Geoscience: Principles, opinion. Guidance on the duties and responsibilities Techniques and Applications. Geological Society, of the expert witness, both in report writing and in London, Special Publications, 232, 159-170. presenting evidence in court, is now widely available EVANS, J. A. & TATHAM,S. 2004. Defining 'local signature' through publications and training programmes (e.g. in terms of Sr isotope composition using a tenth- to Rothwell 1998; Bond et al. 1999; Townley & Ede twelfth-century Anglo-Saxon population living on a 2004). Jurassic clay-carbonate terrain, Rutland, UK. In: PYE, K. & CROFT, D. J. (eds) Forensic Geoscience: Principles, Techniques and Applications. Geological Wider benefits and the way ahead Society, London, Special Publications, 232, 237-248. FENNING, P. J. & DONNELLY,L. J. 2004. Geophysical tech- Involvement in forensic casework often leads to niques for forensic investigation. In: PYE, K. & CROFT, wider benefits, both for the investigating forensic D. J. (eds) Forensic Geoscience: Principles, scientist and for wider geoscience as a whole. The Techniques and Applications. Geological Society, specific requirements of forensic work, relating to London, Special Publications, 232, 11-20. sample continuity, documentation and critical FISHER, B. A. J. 2000. 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