Cartridge case and bullet comparison: examples of evaluative reporting

This paper presents examples of how to report results when using a probabilistic approach in the field of firearms. Three European Institutes who have adopted a Likelihood Ratio (LR)-based approach in their practice were asked to produce the evaluation section of a report based on a fictitious case. Background information about the Institutes, their conclusion scales, and reporting formats is presented. The article ends with a brief overview of recent developments within the ENFSI (European Network of Forensic Science Institutes) community where guidelines for evaluative reports have been formulated and are now published. The current collaborative approach between Institutes, presented in this article, offers an opportunity to discuss practical issues related to this approach. More specifically, this is an opportunity to introduce the ENFSI guidelines and its tenets, providing more tools for firearms/toolmarks examiners to progress towards a LR-based approach.