Francesco I de Medici and his wife Bianca Cappello, both pictured above, died within twelve hours of each other in 1587. Rumors circulating at the time suggested the couple were poisoned by Francesco's brother, Cardinal Ferdinando, who was visiting at the time and who ordered immediate autopsies, presumably to prove a non-toxin-related cause of death -- malaria. Recent research reported in the BMJ shows that "murder will out":
The results of toxicological investigations carried out on the samples identified as biological tissuesand attributable, according to DNA profiling, to Francesco I de' Medici and, tentatively, to Bianca Cappello, and on the femur and beard hair of Francesco I, are consistent with the hypothesis that the Grand Duke and his wife were victims of an acute arsenic poisoning. The 11 day survival time after the onset of the illness could explain the not extremely high—though still in the lethal range, according to the literature—arsenic concentrations measured in soft tissues on the one hand and the very low concentrations detected in bones and hair (insufficient time for significant incorporation) on the other.