Some notes on Are Forensic Scientists Experts? (Alice Towler et al)

I finally read Alice Towler and colleagues’ “Are Forensic Scientists Experts?” (Journal of Applied Research in Memory and Cognition), a very useful and important guide to cognitive science’s current research on expertise and how forensic science (mostly pattern matching) fits into that research. They focus on handwriting analysis, fingerprint examination, and facial image comparison.

As to expertise, the authors say:

Cognitive scientists have studied expert performance for many decades, and as such, are well-placed to examine the question of whether forensic scientists are experts. Prominent researchers in this field have defined expertise as “consistently superior performance on a specified set of representative tasks for a domain”

As to handwriting analysis, the authors’ review finds that experts do not make more correct decisions than novices, but do avoid errors better:

Critically, research across the discipline consistently shows that the difference between handwriting examiner and novice performance is not due to the examiners making a greater proportion of correct decisions. Instead, group differences lie in the frequency of inconclusive and incorrect decisions, whereby examiners avoid making many of the errors novices make…

For fingerprint examiners, they find they are generally pretty accurate but with considerable variation between examiners:

These studies, alongside other work by cognitive scientists, provide compelling converging evidence that trained fingerprint examiners are demonstrably more accurate than untrained novices at judging whether or not two fingerprints were left by the same person … However, they also show low intra-examiner repeatability and, as a group, demonstrate a surprisingly wide range of performance.

Facial identification practitioners also make fewer errors than novices, but some practitioners perform considerably worse than others:

…more recent work has also found superior accuracy in forensic facial examiners compared to untrained novices (Towler, White, & Kemp, 2017; White, Dunn, et al., 2015), suggesting that they are indeed experts. Importantly however, all of these studies focused on group-level differences between novices and examiners. When comparing individual examiners on these tasks, large differences in their performance emerge, with some examiners making 25% errors and others achieving almost perfect accuracy.

Interestingly, they also find that expert fingerprint analysis may rely more on quick and unconscious processes than image comparison.

They end with some calls for more research in this area, which is in its infancy. Worryingly, there is a lot we don’t know about the expertise of “experts”.