A model of evaluative opinion to encourage greater transparency and justification of interpretation in post-mortem forensic toxicology.

Over the past decades, the calls to improve the robustness of interpretation in forensic science have increased in magnitude. Forensic toxicology has seen limited progress in this regard. In this work, we propose a transparent interpretive pathway for use in post-mortem forensic toxicology cases. This process allows the selection of the interpretive methodology based on the amount of previous information that is available for the substance(s) in question. One approach is an assessment of various pharmacological and circumstantial considerations resulting in a toxicological significance score (TSS), which is particularly useful in situations where limited information about a substance is available. When there is a robust amount of case data available, then a probabilistic approach, through the evaluation of likelihood ratios (LRs) by the toxicologist and of prior probabilities by the fact-finder, is utilized. This methodology provides a transparent means of making an interpretive decision on the role of a drug in the cause of death. This will allow the field of forensic toxicology to take a step forward in using best practice in evaluative reporting, a tool already used by many other forensic science disciplines.