Forensic Epidemiology: a systematic approach to probabilistic determinations in disputed matters.

Forensic medicine testimony often relies upon terms of probability to enhance the strength of the testimony. Such terms must have a demonstrably reliable and accurate basis; otherwise their use is speculative, unjustified, and potentially harmful. Forensic Epidemiology is introduced as a framework from which probabilistic testimony can be assessed in settings in which it is either proffered or encountered. In this paper, common forensic uses of probability are reviewed, appropriate methods for presenting such testimony are proposed, and inappropriate uses of probability and epidemiologic concepts and data, as well as a logical fallacies commonly observed in forensic settings are presented. A previously unpublished logical fallacy, the "Prior Odds" Fallacy, is also introduced.