Abstract
Epidemiologists, biostatisticians, and health physicists frequently serve as expert consultants to lawyers, courts, and administrators. One of the most common errors committed by experts is to equate, without qualification, the attributable fraction estimated from epidemiologic data to the probability of causation requested by courts and administrators. This error has become so pervasive that it has been incorporated into judicial precedents and legislation. This commentary provides a brief overview of the error and the context in which it arises.