Scientists who exhumed the remains of several members of the Medicis, the clan that dominated the Florentine Renaissance, have conclusively dismissed the theory of family murders, solving a more than 400-year-old cold case.

Malaria, not poison as long rumored, killed Francesco I de' Medici, Grand Duke of Tuscany, and his second wife, Bianca Cappello, according to research to be published in Transactions of the Royal Society of Tropical Medicine and Hygiene.

The couple died a few hours apart in October 1587 after 11 days of agony. Their almost simultaneous deaths led to speculation that they had been murdered....