Trial by ordeal

Trial by ordeal was a way to decide if someone was guilty or innocent of a crime. This was usually done by causing the accused person to do a painful task. If that task was completed without injury or if the injuries healed fast, this taken as a "sign of God", which meant that the accused was innocent. People believed that God would not allow innocent people to be harmed. He would therefore help them by doing a miracle. There were three common types of Trial by Ordeal: 
Ordeals had to be watched over by a religious person, such as a priest, because each ordeal was supposed to show the judgement of God. In England, Ordeals were common up to and including the reign of Henry II, who introduced Trials by Jury.
In pre-modern society, the ordeal typically was done together with the oath and witness accounts as the central means by which to reach a verdict. The term "ordeal" itself, Old English "ordǣl", has the meaning of "judgment, verdict" (German "Urteil", Dutch "oordeel"), from Proto-Germanic "*uzdailjam" "that which is dealt out".
In Europe, ordeals commonly required an accused person to test himself or herself against fire or water. How this was done varied in detail, and was different at different places and times. In England, ordeals were common under both the Anglo-Saxons and the Normans. Fire was the element typically used to test noble defendants, while water was more commonly used by lesser folk. 
Priestly cooperation in trials by fire and water was forbidden by Pope Innocent III at the Fourth Lateran Council of 1215, and replaced by compurgation. Trials by ordeal became more rare over the Late Middle Ages, often replaced by confessions extracted under torture, but the practice was discontinued only in the 16th century. Johannes Hartlieb in 1456 reports a popular superstition for how to identify a thief by an ordeal by ingestion practiced privately without judicial sanction. 
Trial by ordeal has existed in polytheistic cultures as far back as the Code of Hammurabi and the Code of Ur-Nammu, and in animist tribal societies, such as the trial by drinking "red water" (calabar bean) in Sierra Leone. There the intended effect is magical rather than calling forth justice from a god.