The Limits of Bayesian Thinking in Court

Abstract

We comment on the contributions of Dahlman and of Fenton et al., who both suggested a Bayesian approach to analyze the Simonshaven case. We argue that analyzing a full case with a Bayesian approach is not feasible, and that there are serious problems with assigning actual numbers to probabilities and priors. We also discuss the nature of Bayesian thinking in court, and the nature and interpretation of the likelihood ratio. In particular, we discuss what it could mean that a likelihood ratio is in some sense uncertain.

Towards another paradigm for forensic science?

“…In the Bayesian approach, the case‐based nature of forensic interpretation is integrated as I (background information) in the conditional probability (P(H|E, I) or P(E|H, I)). However, this I is manageable in equations when it is kept simple, that is, the case's particular circumstances are easily integrated (Meester, 2020). This is true in the decontextualized flow of comparisons to the trace‐print chain (where I is the empty set or close to it).…”