Michael Weber - The Truth

You show your friends a pair of bronze tokens which you will use to demonstrate your skill as an infallible lie detector. Your friends secretly select one of the tokens, marked either TRUTH or LIE, and the selected token dictates how they will both answer all of your questions. If they select the TRUTH token, they must answer each question truthfully. If they select the token marked LIE, they must always respond to each question with a lie.

With your back turned, your friends silently decide on one of the two tokens and replace the unselected token in the carrying bag. You ask them to silently decide which of them will hold the token, and that person holds the coin in either his right or left hand, (but he need not tell his friend in which hand it is hidden.)

Stand across the room, turn around and face your friends, and ask only two questions: First you ask one friend, “Does he have the coin?” After listening to the response you ask your other friend, “Is the coin in your left hand?”

Both must respond according to the word embossed on the cho- sen token, by consistently lying or telling the truth.

At this point you know everything, even from across the room. You can now confidently state, “There are two people, two choices of how to answer my questions, and four different hands in which the coin could be hidden. I am certain that Bob does not have the coin, that Steven does have the coin, and that Steven is hiding it in his left hand. I know this because I can tell that both of you are lying. When Steven opens his left hand, the LIE token is, in fact, hidden inside.

This effect can be performed for one or more persons and can be repeated, and your spectators will be able to choose a different token each time.
The objects are exactly as they appear to be and can be examined before and after your demonstration.