In the fall of 1761, the Calas family found their oldest son hanging. Immediately they called the authorities. At first, they said that someone must have murdered the young man. A few days later the authorities arrested the family for the murder.
At that point, their story changed. The family, now said that their son hung himself. They originally said murder because they worried about his burial and soul. The church condemned suicide. No one who committed suicide could enter heaven.
Still, the court convicted Calas of murdering his son. The next day they tortured him, trying to get a confession. They then killed him. He never confessed and maintained his innocence to the end.
Voltaire eventually heard about the case. At first, he agreed with the conviction, then he heard more facts and changed his mind. He spent two years diving into the French judicial system, trying to clear the name of Calas. He finally succeeded in 1765, when posthumously, the court acquitted Jean Calas of the murder, restoring his good name. Voltaire continued for several more years helping other wrongly convicted people.