Book Review: Interpreting Evidence: Evaluating Forensic Science in the Courtroom
| Author | Oriola Sallavaci |
| DOI | 10.1177/1365712716686416 |
| Published date | 01 October 2017 |
| Date | 01 October 2017 |
| Subject Matter | Book Review |
Book Review
Interpreting Evidence: Evaluating Forensic Science in the Courtroom. By Bernard Robertson,
G. A. Vignaux and Charles E. H. Berger. 2nd edition, 2016.
The legal system has long made use of forensic evidence to assist fact finding. This use has significantly
increased in recent decades due to scientific and technological advances. When science and law coincide
at court, tensions may arise that present direct challenges to traditional legal structures and procedures,
as well as the weight attributed to the scientific evidence. At the heart of these conflicts lie the complex-
ity of scientific evidence a nd the lack of familiarity on the p art of lawyers with the method s and
principles of evidence interpretation applied by the scientific witness. On the other hand, difficulties
are compounded by insufficient und erstanding on the part of witnesses o f the legal reasoning and
strategies internal to the trial process. These often manifest because of a failure of communication
between lawyers and experts.
Courts are concerned with what can be inferred from the observations made by the scientist. The
methods adopted by both the defence and prosecution to evaluate physical evidence and cross-examine
opposing expert witnesses often are the decisive factor in a case. This is the central theme that runs
throughout this book. The authors emphasise that scientific evidence should be presented in such a way
that lay people can easily interpret and weigh it, as well as understand how to combine it with other
evidence in the case. To this end, the authors propose that ‘logic, probability and inference provide the
common language in which the two groups’, lawyers and scientists, ‘should communicate with each
other’ (p. 180).
In the first six chapters of the book the authors explain the fundamental principles of what they refer
to as ‘logical reasoning about evidence’ and how they apply to all forms of evidence in both criminal and
civil cases. The authors deal with the types of questions that forensic evidence can answer and how the
strength of that evidence can be explained. Scientific evidence, like any other type of evidence, should
not be expected to provide certainty. While often such evidence is misunderstood and deemed unreliable
or inadmissible, the authors argue that uncertainty is inherent to the limited amount of information that
can be extracted by the examination of physical evidence. A scientific witness will not be able and
should not be expected to say that two samples came from the same person. The evidence can only lead
to an assessment of the probabilities that the evidence would be found if the prosecution case was true
and if the defence case was true. This comparison is expressed through the likelihood ratio.
The authors emphasise that expert evidence and expert opinion should be restricted to the reporting of
a likelihood ratio which expresses the value of the evidence for the hypotheses considered. The hypoth-
eses being compared must be exclusive but need not be exhaustive. They should reflect the position
taken by the parties in the case and must be chosen and phrased appropriately. When the alternative
hypothesis changes, the value of the evidence determined by its likelihood ratio changes as well.
The authors explain how individual items of evidence should be thought about by using the logical
approach. The probative value of a particular item of evidence is directly related to the likelihood ratio
and the value of the likelihood ratio reflects the logical evaluation of the evidential value of the
The International Journalof
Evidence & Proof
2017, Vol. 21(4) 371–372
ªThe Author(s) 2016
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DOI: 10.1177/1365712716686416
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