Pollen in the courtroom: enhancing forensic palynology with quantitative modelling

Pollen grains are tiny, widely dispersed, and can be recovered in large numbers from small samples of a variety of contexts from soils to human hair and clothing. Forensic palynology, the use of pollen assemblages recovered from samples associated with criminal investigations as a line of evidence, has been used since the 1950s, and largely uses the methods and interpretive frameworks developed by ecological and archaeological palynologists working mostly with samples taken from sediments accumulating in lakes/mires. In this paper, we explore whether recent methodological developments in those allied fields can contribute to improving the robustness and objectivity of assemblage interpretation in forensic palynology.
We demonstrate that models of pollen dispersal and deposition can improve the interpretation of assemblages from some sample contexts and provide additional supporting evidence. We also propose an approach to incorporating quantitative estimates of post-depositional changes in assemblages into interpretations, since some forensic samples are taken from contexts which are not ideal for pollen preservation. Both methods are only appropriate for a subset of forensic palynological samples, and we present a workflow to identify suitable situations in which to apply these interpretive tools, if investigating budgets allow. We demonstrate the potential of these approaches and set out a research programme to both better define when these methods should be used and strengthen the underlying evidence base. Thoughtful incorporation of methodological developments in allied fields has the potential to improve interpretation of forensic palynology samples and strengthen the evidence presented as well as arguments made in court.