Forensic Evidence in Court: Evaluation and Scientific Opinion

Book Preface

This book is about how science and scientific opinion impinge upon and influence legal debate. It is written by a scientist, principally for an audience of scientists, more specifically for those in the later stages of an undergraduate degree in forensic science, studying at postgraduate level or working as practitioners. As such, a basic understanding of the discipline and of technical matters relating to evidence examination and analysis is assumed, although relevant science is recapped and expanded upon where appropriate. The context throughout is the court of law. Legal cases from across jurisdictions, including principally those based on the Anglo American legal system, are used to demonstrate the evolution of expert opinion, to illustrate the difficulties faced by the scientists and the legal professionals and to provide a real world backdrop to material intended for exposition and discussion in the lecture room.

Although this book is an educational text and not a research monograph, this field of study is subject to developments and advances from both the professional and academic spheres. It is relevant therefore to include some discussion of the scholarship that underpins professional practice and, more specifically, I have incorporated recent research that seeks to resolve current difficulties and may impact directly on expert testimony in the future.

To meet the aims of this text the material is organised within three sections. The first serves the dual purpose of setting the scene, by reviewing the impact of forensic science in the courts over the past thirty years, as well as providing the overall context within which methods for interpretation and evaluation of scientific evidence have been and continue to be developed. This is followed by five chapters in which the focus centres on the forensic scientist as expert witness and ways in which scientific opinion may be formulated from the interpretation of experimental findings, particularly through logical evaluation by likelihood ratio; this includes discussion of many of the issues around the delivery of such opinion.

The final section presents scientific opinion in the context of evidence types. Starting from full DNA profiles where quantitative approaches are informed by rigorously derived databases, the discussion moves to other types of evidence such as footwear marks, glass and fibres where the interpretation may be more qualitative and the associated databases more open to challenge. Later chapters deal with evidence such as handwriting and bloodstain pattern analysis where opinion is formulated much more in accordance with the experience of the individual expert and indeed where the members of the court may believe they can achieve their own evaluation by reviewing the evidence for themselves.

I am very grateful to Dr Ian Evett CBE and Mr Mike Allen for reading and commenting on draft sections of this text. I trust that I have been able to use their feedback to improve the accuracy and clarity of the discussion but the final responsibility for that, of course, must rest with me. I also wish to thank my wife, Alison, for her invaluable advice, patience and support throughout the development and writing of this book.

raig Adam,
January 2016