A more thorough explanation:

Definition: Canfara is a trial by hot iron that was used in England in the past. It was a primitive form of trial where an accused person was subjected to a dangerous or painful physical test, and the result was considered a divine revelation of the person's guilt or innocence. The participants believed that God would reveal a person's culpability by protecting an innocent person from some or all consequences of the ordeal. The ordeal was commonly used in Europe until the 13th century, but only sporadically after 1215, when the Fourth Lateran Council forbade the clergy from participating in ordeals.

Examples:

• Ordeal by fire: An ordeal in which the accused person was forced to hold a piece of hot metal or to walk barefoot across a hot surface, the judgment of guilt or innocence depending on how quickly and cleanly the person's hands or feet healed. Typically the person's hand was bandaged and, upon the bandage's removal three days later, was examined for festers (indicating guilt).
• Ordeal by water: An ordeal in which guilt or innocence depended on whether the accused person floated or sank after being submerged in cold water. A priest would first consecrate the pool of water, adjuring it to receive the innocent but reject the guilty. An accused who sank was declared innocent; one who floated was adjudged guilty because floating revealed the water's (and therefore God's) rejection of the person.
• Ordeal of the morsel: An ordeal in which the person who was to make the proof was given a one-ounce piece of bread or cheese that a priest had solemnly charged to stick in the throat of the guilty. A person who choked was declared guilty; a person who did not was declared innocent.

The examples illustrate how the ordeal worked and how guilt or innocence was determined. In the ordeal by fire, the accused person had to hold a hot metal or walk barefoot across a hot surface, and the judgment of guilt or innocence depended on how quickly and cleanly the person's hands or feet healed. In the ordeal by water, the accused person had to float or sink after being submerged in cold water, and the judgment of guilt or innocence depended on whether the person floated or sank. In the ordeal of the morsel, the person who was to make the proof was given a piece of bread or cheese that a priest had charged to stick in the throat of the guilty, and the judgment of guilt or innocence depended on whether the person choked or not.