Bayesian Networks for Probabilistic Inference and Decision Analysis in Forensic Science, 2nd Edition

Chapter 3Evaluation of scientific findings in forensic science

3.1 Introduction

Consider a legal setting. At the times of the preliminary investigation and trial, the proof of a point at issue may be assisted through information that often takes the form of results of comparative examinations and that relies on forensic science. Such scientific findings may be used to draw inferences about the existence or the nature of a criminal act (for example in forgery cases) or to help evaluators characterize relationships between elements involved in an act under investigation, such as an aggression between an offender and a victim in a sexual assault case. In the latter case, scientists may conduct comparative analyses of multiple traces (such as DNA or textile fibres) for which transfer is typically expected to occur.

Developments during the last 20 years have greatly increased the range of possible types of traces and the scope of analytical techniques that have been presented to the courts. These developments have allowed scientists to analyse a broader scope of traces, and traces of increasingly reduced size or amount. However, it is not only the mere results of analyses as such that should be presented to a court. Results need to be evaluated and interpreted in the context of the case under trial.

Scientific outcomes require considerable care in their interpretation, and it is particularly important to focus on questions of the kind ‘What do the results mean in this particular ...