Communicating forensic science opinion: An examination of expert reporting practices

Abstract

Forensic scientists endeavour to explain complex scientific principles to legal decision-makers with limited scientific training (e.g., police, lawyers, judges, and jurors). Much of the time this communication is limited to written opinions in expert reports. Notwithstanding considerable scientific research and debate about the best way to communicate forensic science opinions, it is unclear how much of the advice has translated into forensic science practice. In conducting this descriptive study, we examined the reporting practices adopted by forensic scientists across a range of forensic science disciplines. Specifically, we used a quantitative content analysis approach to identify the conclusion types and additional information submitted by forensic scientists in proficiency tests during 2016 ("What would be the wording of the Conclusions in your report?"). Our analysis of 500 randomly selected responses in eight disciplines indicated that the conclusion type which has received the most criticism in recent years (categorical statements) remains the preferred means of expression in a clear majority of responses. We also found that the provision of additional information often considered necessary for rational evaluation of the evidence (e.g., information about reliability and validity) was rarely reported. These results suggest limited engagement with recent recommendations and are concerning given the gravity of the legal decisions that hinge on accurate and transparent forensic science communication.

Keywords: Communicating opinion; Expert evidence; Expert reports; Forensic science; Proficiency testing; Uncertainty.