A guide to interpreting forensic testimony: scientific approaches to fingerprint evidence

In response to criticism of latent fingerprint evidence from a variety of authoritative extra-legal inquiries and reports, this essay describes the first iteration of a guide designed to assist with the reporting and interpretation of latent fingerprint evidence. Sensitive to the recommendations of these reports, we have endeavoured to incorporate emerging empirical evidence about the matching performance of fingerprint examiners (i.e. indicative error rates) into their testimony. We outline a way of approaching fingerprint evidence that provides a more accurate—in the sense of empirically and theoretically justified—indication of the value of fingerprint evidence than existing practice. It is an approach that could be introduced immediately. The proposal is intended to help non-experts understand the value of the evidence and improve its presentation and assessment in criminal investigations and proceedings. This first iteration accommodates existing empirical evidence and draws attention to the gap between the declaration of a match and positive identification (or individualization). Represented in this way, fingerprint evidence will be more consistent with its known value as well as the aims and conduct of the accusatorial trial.