Homemade Lie Detector
This urban legend is in fact an ancient international story about a thief that is tricked into revealing his guilt. The essence of the trap is that a group of suspects, one of whom is obviously guilty, is told that a certain object, if touched, will magically identify the true thief of all of the suspects. The guilty person of the group is the only one to not touch the object, which is usually smeared with a substance that shows up only on the hands of those that are innocent.
The “lie detector” may be an animal such as a raven under a pot, a donkey soaked in a mint solution, or a sheep with soot-blackened fleece. Supposedly, the animal would make a noise when the thief touches it, but the real indicator is the lack of soot or mint on the thief’s hands.
In most versions of the story, the touching done on the object takes place in the dark or behind a curtain so the thief thinks that no one can see him failing to touch the object. The idea is that whatever the object is, it would have a substance on it so that when the suspects touch it, it will leave a mark. If the thief doesn’t think that anyone is watching by it being dark in the room, he will not touch it to ensure that he doesn’t get caught. This is the idea of the homemade lie detector, tricking the guilty person into admitting his guilt by basically not doing anything at all.
(Source: Brunvand, Jan H. Encyclopedia of Urban Legends. 2001.)
