Why the post-identification era is long overdue: Commentary on the current controversy over forensic feature comparison as applied to forensic firearms examination

Abstract

In this commentary, we critically review recurring arguments for and against the discipline of forensic feature comparison as applied to firearms examination from various commentators within and outside forensic science. One of the mainstream criticisms that we address, among others, is that the field cannot demonstrate sufficient proficiency and robustness based on empirical (i.e., black-box) studies. While the lack of empirically demonstrated examiner proficiency is a valid concern and a powerful concept in the short term (e.g., in admissibility proceedings), many critics reduce their discussion of forensic feature comparison solely to the need to measure and demonstrate proficiency through error rates. However, the exclusive focus on aggregate expert performance metrics, here referred to as examiner diagnosticism, remains a surface-level perspective. It provides an incomplete account of the field because these metrics do not represent—but are often confused with—the notion of the evidentiary value of findings, i.e., observations made on examined items in individual cases. We argue that examiner diagnosticism should be contrasted and complemented with the notion of feature selectivity, i.e., the diagnostic capacity of observed marks and features on examined items. We argue that forensic scientists should report and be probed on their ability to quantify feature selectivity (i.e., the probative value of findings). By ceasing to express source attribution opinions (identification/individualisation), which are now widely exposed as unscientific, the forensic feature comparison disciplines could move further into the long-awaited post-identification era pioneered by other fields such as forensic genetics.