Jean Calas (1698-1762), a Protestant merchant at Toulouse, whose legal murder is a celebrated case in French history. His wife was an Englishwoman of French extraction. They had three sons and three daughters. His son Louis had embraced the Roman Catholic faith through the persuasions of a female domestic who had lived thirty years in the family. In October 1761 another son, Antoine, hanged himself in his father's warehouse. The crowd, which collected on so shocking a discovery, took up the idea that he had been strangled by the family to prevent him from changing his religion, and that this was a common practice among Protestants. The officers of justice adopted the popular tale, and were supplied by the mob with what they accepted as conclusive evidence of the fact. The fraternity of White Penitents buried the body with great ceremony, and performed a solemn service for the deceased as a martyr; the Franciscans followed their example; and these formalities led to the popular belief in the guilt of the unhappy family.

Being all condemned to the rack in order to extort confession, they appealed to the parlement; but this body, being as weak as the subordinate magistrates, sentenced the father to the torture, ordinary and extraordinary, to be broken alive upon the wheel, and then to be burnt to ashes; which decree was carried into execution on the 9th of March 1762. Pierre Calas, the surviving son, was banished for life; the rest were acquitted. The distracted widow, however, found some friends, and among them Voltaire, who laid her case before the council of state at Versailles. For three years he worked indefatigably to procure justice, and made the Calas case famous throughout Europe (see Voltaire). Finally the king and council unanimously agreed to annul the proceeding of the parlement of Toulouse; Calas was declared to have been innocent, and every imputation of guilt was removed from the family.

See Causes célèbres, tome iv.; Raoul Allier, Voltaire et Calas, une erreur judiciaire au XVIIIe siècle (Paris, 1898); and biographies of Voltaire.