We used to do the same in England... but we were civilised about it and had a foolproof system. What used to happen is that the soceress (or witch) was tied to a chair on the end of a long pole. She would then be dunked in to a river for 10 minutes. If she was truly a witch, then she would escape and fly away. If she was innocent, then she would be given a decent Christian burial and her name cleared.

Witches beware!