Foundations of Forensic Document Analysis

Theory and Practice

Michael J. Allen

• Verlag: Wiley-Blackwell
• Jahr: 2015
• ISBN:
  9781118729908
• Auflage: 1
• Thema: Medicine
• Thema: Forensic Medicine

Forensic document examination is a long established specialty and its practitioners have regularly been shown to have acquired skills that enable them to assist the judicial process. This book, aimed primarily at students studying forensic science and document examination in particular, introduces all of the essential ideas that are to be found in the work of the forensic document examiner in a concise and straightforward way. Each examination type is described not only in terms of its procedural basis but also the science and reasoning that underpins it. The reader will be able to relate the different kinds of interpretation skills used by the document examiner to those used in other forensic disciplines.

This book will be an invaluable text for all students taking courses in Forensic Science or related subjects. The book will also be a useful reference for researchers new to this field or practitioners looking for an accessible overview. The author will be adding new references that are relevant as they are published and some more worked examples from time to time. Please visit qdbook.blogspot.co.uk for more details.

Chapter 1
Introduction

Forensic document examination, like all forensic specialties, is first and foremost based on knowledge. However, there are many other important aspects to the job that should not be overlooked because knowledge on its own is not enough to ensure the competence of experts. In this chapter these other aspects are described to give the reader some idea about these issues, which are easily overlooked but which are vital if the quality of forensic procedures is to be fit to be put before the courts.

1.1 Historical background

Just when and where writing started is not certain, but it has been around for thousands of years and probably first appeared in the eastern Mediterranean, at least partly driven by the need to record trading transactions among seafaring nations such as the Phoenicians – who may have been the first to create an alphabet.

Whatever its historical origins, once people started to write it was inevitable that others would start to abuse the written form for fraudulent reasons. In the intervening years, the criminal motivations have probably changed very little but the means to achieve them have changed beyond all recognition.

Document examination, and in particular handwriting examination, has been a recognised specialty in the context of the judicial systems of many countries for well over 100 years. Part of the reason for its early inclusion centres on the importance of handwriting, and in particular signatures, as a mark of agreement and endorsement to authorise various business and other transactions. The need for a third (independent) party to give an opinion about the genuineness, or otherwise, of disputed signatures and handwriting can readily be appreciated.

As technology developed in the late nineteenth and throughout the twentieth century new problems for document examiners arose in tandem with the expansion of business and commerce across the world, and as a result much of the work of the expert is concerned with commercial transactions. Nonetheless, the domestic environment continues to produce its share of cases, from anonymous letters to ransom demands to murder and terrorist activities.

Other strands of document production have their own separate histories, such as the production of paper, the use of printing, advances in ink formulation and writing implements and the development of the typewriter and its eventual replacement by the computer printer. The many faceted work that faces the document examiner tasked with determining a document's authenticity has made the specialty a mainstream forensic discipline present in forensic science laboratories across the world.

In the early days of the specialty, textbooks on document examination were few and far between and they generally focused on handwriting and signature examination, but in 1910 in the USA the first book to draw the disparate examination types together into one place was written by Albert S. Osborn and entitled Questioned Documents. Since then a number of textbooks have been written, each one able to give more up-to-date information as methods have improved and developed.

While document examination is widely regarded as a mainstream forensic specialty, and certainly there is no disputing the need for experts in this discipline if cases involving documentation are to be prosecuted, one question that needs answering is: Are the underpinning foundations of document examination robust? Or put another way, can the courts rely on the evidence that forensic document examination provides (and that individual practitioners present in a given case)?

1.2 Is document examination a science at all?

Forensic science, by its high profile nature and the considerable public interest in the subject – both in the real world and in fiction, is perhaps one of the most scrutinised of scientific endeavours. Given the consequences that arise from it (fines, imprisonment and more depending on the country) it is of course quite right that all areas of forensic science should be able to justify themselves so that the public can be as sure as is humanly possible that the evidence presented to the courts is the best available.

And there is the first (and most intractable) problem – forensic science is a human endeavour – it does not exist in a world where uncertainty and error are somehow suspended in striving for absolute perfection and reliability. The possibility of error should be the single biggest factor influencing practitioners as they endeavour to maintain as high a standard as possible in all that they do, as they determine the evidence in a case, and especially when assessing the weight of their evidence. Most of forensic science ultimately comes down to interpreting evidence, and that is a cerebral process conducted by the expert, whatever the specialty, based on whatever evidence has been discovered and evaluated. Thus, using technology to detect, analyse and measure amounts of material (be it drugs in the body or DNA on clothing) is often just the foundation upon which the expert's opinion is based. There are instances when the technology may effectively be providing the expert evidence – such as identifying what a suspicious white powder is (of course, using the technology correctly is itself an endeavour requiring expertise). But expert evidence is human opinion evidence, not machine-generated data. Indeed, one of the most important factors that defines expert witnesses is that they are allowed to, indeed are encouraged to, express an opinion about the significance of their findings. Opinion evidence is almost forbidden from other categories of witness in many legal jurisdictions.

In this context, the specialty of document examination will be seen in the following chapters to have to admit that it does not always have many databases upon which to call when assessing evidence. The greatest focus of criticism of the specialty has generally been on handwriting and signature examination (Risinger et al. 1989). As we will see in this book, much work has been done by various researchers to address some of the criticisms and in so doing provide reassurance that the knowledge and processes that underpin the specialty of document examination are of sufficient reliability to justify their use. The capability of individual practitioners is a separate matter that also needs consideration.

In many areas of science, the use of computing power has transformed the methods and procedures used and it is not surprising that this is also true in document examination, particularly so in handwriting and signature identification. Perhaps one of the principal motivations for such an approach is to remove (or reduce) the human element of the expert's opinion and replace it with a mathematical (non-human) result based upon a de-personalised evaluation of the evidence. In Chapter 2 some consideration is given to the use of computers in handwriting examinations. The fact is, however, that despite considerable amounts of research into computer-based methods of assessing handwriting, no method has emerged to replace the human expert. At best, some of the findings of these research endeavours provide assistance to, but in no way yet replace, the human expert.

The reason for this is that of all of the ‘things’ that forensic practitioners examine (from paint to glass to body fluids), handwriting is unusual in being the constantly varying physical product of the human mind and body, unlike any other physical material that forensic science tries to examine. (Some of the closest relations are forensic phonetics and forensic linguistics, which seek to examine the human voice and the way that we use language, respectively, and forensic gait analysis, which assesses how we move as we walk.) Handwriting examination does not have the luxury of having invariant materials to look at, be they glass fragments, flakes of paint, or stains from biological fluids, the analyses of which do not have to cope with intrinsic natural variability let alone variability that is under human control.

It can readily be seen why technological solutions that address questions such as ‘what is this thing made of’ are less difficult to answer than questions such as ‘who did this handwriting’, for example, given that every piece of handwriting is unique and people may deliberately try to disguise their writing or else someone may try and copy their handwriting. How does a computer [operator] factor in even those basic issues since there are no global rules that dictate how good or bad a particular person is at writing (or how variable it is), disguising or copying?

The study of handwriting can currently only be carried out by human practitioners, albeit potentially with some assistance from computers that can provide some supporting information in some instances. The processes involved in handwriting comparison are described in Chapter 2. In some ways the requirements are really quite simple to describe, as in essence they require a forensic document examiner to undertake a lot of study around the subject and gain experience in examining handwriting from many people in many case situations to build up a personal database of experience and information. This may seem to be a cause for concern since this leads to experts forming opinions based on reasons that are not freely available in the public domain but are rather based on thoughts that occur in their heads. This misses the point that experts must be able to show they have followed appropriate methods (such as those described in Chapter 2) and they must be able to demonstrate and justify their opinions to others (such as the court). Any specialty that allowed practitioners to say ‘This is my expert opinion, take it or leave it’ would rightly be discounted. Ironically, the more technologically advanced the methods used by a forensic practitioner, the more there is an element of trust between their evidence and those using it, simply because the complexity of the technology is beyond the understanding of the lay person. Indeed, the actual working of a piece of equipment may not be fully understood by the person operating it, but the results obtained from it (from which the evidence is then derived) are of course understood.

Science can be defined as an intellectual and practical activity requiring the comprehensive study of the structure and behaviour of the world by observation and experiment. Looking at the elements of this definition in relation to handwriting, the activity of handwriting examination encompasses both intellectual (interpreting what is observed) and practical (observing and recording findings) aspects. The examination process is comprehensive (it is based on a thorough and complete process not focusing on isolated aspects). The relevant structure is in the handwriting (and an understanding of its physiological origins) and the behaviour is covered by an understanding of the capabilities of people when writing. The experimental dimension is given in the body of published knowledge that can be drawn on by practitioners. And careful observation is the single most important element of the examination process whatever the forensic specialty.

The notion that science somehow exists outside of human endeavour, in particular in a machine-based, infallible and statistically perfect world, is not only wrong, it is potentially dangerous precisely because the human elements of understanding and interpretation can be all too readily subsumed to a machine that then conveniently becomes the source of error (thereby allowing a practitioner to be absolved from any implied criticism when an error occurs). This diminishes the role of the (human) expert to the point where personal responsibility for the evidence placed before, say, a court is deflected to machines.

Looking at this another way, there is an expectation that human forensic practitioners are infallible when presenting their evidence. This is as unreasonable as it is ridiculous. No aspect of human endeavour can live up to such a high level of pressure, not medical science, not computer science, not even the law.

The National Academy of Sciences report (National Research Council, 2009) into forensic science added another layer to this debate by insisting that any specialty should justify its methods and also require a process of ensuring that individual practitioners can demonstrate an appropriate level of competence. In other words, there is a (deceptively) simple two-stage process needed to make sure that the science is good and that the scientist is good, or more broadly, that the methods used in any forensic specialty are good and the practitioners are good (hence side-stepping the issue of just what constitutes science with all of the mental baggage that ...