Criminal Intent by Zanadu Magic - Trick

Effect:
A card is selected, returned to the deck and shuffled. The magician explains how this card will be located by using the technologies of forensic science. "You selected one card, therefore your fingerprints can be found on one card in this deck."

Cards are spread face down and the entertainer proceeds to take out a miniature UV light. "I'm sure you've seen a number of crime scene and investigative forensic shows. They use luminal to detect blood, and a device like this one to see fingerprints and fibers." The light is turned on and waved over the deck, suddenly glowing images and fingerprint marks can be seen on one card only. The card is turned over and it turns out to be the spectator's selected card! The rest of the deck can be examined.