Lead Poisoning in France around 1840: Managing Proofs and Uncertainties in Laboratories, Courtrooms, and Workplaces

Abstract

This article reviews one of the most famous cases of lead poisoning in France, the Ponchon affair, which occurred in 1843 during a crucial period for French toxicology. The trial attracted public attention and inflamed controversy among medical and legal experts. The debate involved toxicological methods and their reliability, and gave rise to more general questions about the value of expert evidence, the way it was presented in court, and its relationship to other forms of legal evidence. I begin with a general overview of lead poisoning and toxicological research on lead compounds around 1840. I then discuss different toxicological proofs employed for detecting or preventing lead poisoning and examine as well growing uncertainties about them. A review of several trials related to lead poisoning in workplaces around 1840 introduces the Ponchon affair. Here I present the experts involved in the trial and describe their strategies for presenting and managing proofs and uncertainties. Finally, I summarise the controversy aroused by the trial in medical and legal communities as it relates to the value of jury trials in cases of poisoning, the risks of using too much chemistry in judicial inquiries, and the different proposals for managing uncertainties and disagreements among experts.