Fingerprint Development Techniques

Theory and Application

Stephen M. Bleay, Ruth S. Croxton, Marcel De Puit

• Publisher: Wiley
• Year: 2018
• ISBN:
  9781119187448
• Edition: 1
• Topic: Medicine
• Subtopic: Forensic Medicine

A comprehensive review of the latest fingerprint development and imaging techniques

With contributions from leading experts in the field, Fingerprint Development Techniques offers a comprehensive review of the key techniques used in the development and imaging of fingerprints. It includes a review of the properties of fingerprints, the surfaces that fingerprints are deposited on, and the interactions that can occur between fingerprints, surfaces and environments. Comprehensive in scope, the text explores the history of each process, the theory behind the way fingerprints are either developed or imaged, and information about the role of each of the chemical constituents in recommended formulations.

The authors explain the methodology employed for carrying out comparisons of effectiveness of various development techniques that clearly demonstrate how to select the most effective approaches. The text also explores how techniques can be used in sequence and with techniques for recovering other forms of forensic evidence. In addition, the book offers a guide for the selection of fingerprint development techniques and includes information on the influence of surface contamination and exposure conditions.

This important resource:

• Provides clear methodologies for conducting comparisons of fingerprint development technique effectiveness
• Contains in-depth assessment of fingerprint constituents and how they are utilized by development and imaging processes
• Includes background information on fingerprint chemistry
• Offers a comprehensive history, the theory, and the applications for a broader range of processes, including the roles of each constituent in reagent formulations

Fingerprint Development Techniques offers a comprehensive guide to fingerprint development and imaging, building on much of the previously unpublished research of the Home Office Centre for Applied Science and Technology.

1
Introduction

Stephen M. Bleay¹ and Marcel de Puit²

¹ Home Office Centre for Applied Science and Technology, Sandridge, UK

² Ministerie van Veiligheid en Justitie, Nederlands Forensisch Instituut, Digitale Technologie en Biometrie, The Hague, The Netherlands

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Key points

• The traces left by contact between the hands and other surfaces are an essential tool in forensic investigations.
• Such traces can be used in several ways: to provide contextual information about the contact event and to identify individuals.
• All potential forensic applications of such contact traces rely on them being visualised by some means.

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There are several books that deal with how latent fingermarks, and to some level the visualisation thereof, are used for identification purposes. To a great extent, the comparison and identification of latent fingermarks in criminal investigations remains their principal application.

In this book we will describe the chemistry (and other properties) of fingermarks in more depth and describe how fingermarks can be used for more than just identification purposes. We will describe how fingermarks may be deposited, the chemical and biological composition of the fingermark and its physical properties, the chemical and physical techniques used to visualise latent fingermarks and the importance of combining fingermark visualisation with recovery of other forensic evidence. Consideration is also given to the importance of communication between individuals visualising fingermarks and those responsible for their comparison and identification.

The traces that may be left by the contact between the palmar regions of hands and a surface are potentially the most informative forms of evidence available to the forensic scientist. The skin on the inside of the hands can flex and adapt to perform a wide range of manipulative tasks, and there are few actions (legal or illegal) that can be carried out without holding objects and/or touching surfaces. The nature of each of these contacts will be different, but in all cases Locard’s exchange principle (Locard, 1934) applies, and there is the potential for the transfer of material between the hand and the surface.

In the context of crime investigation, there are many levels of information that can potentially be extracted from these areas of contact if it is possible for a forensic scientist to first locate and then enhance and analyse them.

At the coarsest level, the configuration of the palm and fingers during the contact with the surface and their position on it can provide useful contextual information about how the surface was touched or gripped. This can be particularly useful in corroborating or disproving particular accounts of events. Figure 1.1 illustrates a situation where the one individual claimed that an assailant had grasped his shirt, whilst the other individual claimed that he had merely pushed the wearer of the shirt away.

Figure 1.1 A contact (grab) mark on a black cotton shirt developed using vacuum metal deposition.

Reproduced courtesy of the Home Office.

The mark that has been revealed suggests that the fabric of the shirt has been gathered together by the hand, and therefore the account of the shirt being grasped by an assailant is more likely than a push with an open hand. Figure 1.2 shows two different orientations of fingermarks on a glass bottle.

Figure 1.2 The orientation of fingermarks on a glass bottle originating from different actions. (a) Bottle being held to drink from. (b) Fingermarks developed using aluminium powder after drinking. (c) Bottle being held as if to strike. (d) Fingermarks developed using aluminium powder after use as a weapon.

In the first case, the bottle has been held whilst drinking from the neck of the bottle. In the second case, the bottle has been gripped as if the bottle has been picked up for use as a weapon. Again, by examination of the configuration of the marks, it may be possible to infer how an item was handled, and this may become evidentially important.

Obviously, there are many more possible scenarios than the two examples presented here, and it should be noted that these are merely illustrative examples. In real casework the propositions (hypotheses) and subsequent examinations are likely to be more complex.

Revealing the distribution of a contaminant (an exogenous material) on the hand may also provide useful information that can be indicative of certain actions. In another example, the firing of a gun will result in the transfer of gunshot residue onto the hands (Figure 1.3). Although the hands can be swabbed to reveal the presence of gunshot residue, if its distribution across the hand can be shown, this may be far more useful in showing that it was much more likely that the gun was held and fired rather than the residue coming from accidental contact. This distribution of contaminant may also be subsequently reproduced in any marks left by the hand.

Figure 1.3 A white gelatin lift taken from the back of the hand taken after firing a gun and enhanced using a chemical selectively targeting traces of lead.

Reproduced courtesy of the Home Office.

At a slightly finer level, a closer analysis of the areas of palm and finger contact can also reveal information about the events during the time of contact. Although many of these events may consist of single, light contacts, others may be of longer duration and may include movement of the hand or multiple contacts, for example, as a grip on an object is readjusted. By analysis of the traces left by the contacts, it is possible to ob...