Expert evidence matters but is probably underused by defence lawyers. Understanding its true value is critical to both prosecuting and defence lawyers.
The evidence needs to be presented and understood. It cannot be left entirely to opposing experts, not least because, as this book emphasises, the quality of evidence will depend on the detail of the instructions that are given. The defence case statement has a particular significance, as it may introduce new hypotheses that will affect the likelihood ratio central to the arguments advanced in this text.
This book will be as valuable to civil lawyers. It argues that forensic evidence should be seen as part of the totality of evidence.
The first edition was published in 1995 and it has been significantly updated. Each chapter sets an objective and concludes with a clear summary of the points made. It is not always an easy read. The concept of the likelihood ratio and the log likelihood ratio is hard for a lawyer to understand.
Authors: Bernard Robertson, G.A. Vignaux and Charles E.H. Berger
Yet, in preparing cases and particularly in presenting and testing expert evidence, there is a great deal of valuable material. The book emphasises that courts are less often concerned with reliability or accuracy, but rather with how the expert evidence may be interpreted and presented to a jury.
Several sections are especially valuable to a criminal practitioner and alone are worth reading. The section on the misuse of words is particularly revealing–‘consistent’ means no more than ‘not inconsistent’; the explanation of the prosecutor’s fallacy; the meaning of phrases in describing the support the evidence gives as weak, moderate, strong, very strong, and extremely strong. The book argues, for instance, that the words ‘reliability’ and ‘match’ should never be used. It also has a good section on the traps deriving from the use of databases.
Faced with expert evidence, both litigator and advocate may be pleased to turn to this book in an attempt to understand its real significance.
Anthony Edwards is a solicitor at TV Edwards. He was a member of the Justice working party on long and complex trials