Lie Detector is a classic plot in card magic in which a magician can detect the selected card by having the spectator's purposely miscall it.
First suggested by Vincent Dalban in a letter sent to Theodore Annemann on December 5, 1934. Annemann published in Jinx January 1935 (No. 4) as a posed problem. The original plot as proposed by Dalban:
- "The member of the audience shuffles the pack of cards and then, while the performer’s back is turned he deals the cards slowly face up onto the table, each time calling aloud the name of each card as dealt. Occasionally, he deals one card and calls the name of another but whenever he does this the performer pulls him up at once. The performer seems to know when the man is telling a lie."
Lie Speller is a variation developed by Martin Gardner in the 1930s in which the spectator answers questions and is allowed to lie or tell the truth as the magician spells out the answer using the cards, the selected card ends up being the last card dealt.
- Martin Gardner's Lie Speller in Joe Berg's Here's New Magic (1937)
- Newspell by Martin Gardner in The Jinx Winter Extra 1937-1938
- That's The Way They're Done in My Best by J.G. Thompson, Jr. (1945)
- The Illogical Lie Detector, page 23 By Ed Marlo in New Tops, Vol. 21, no. 5, may 1981.
- To Lie or Tell the Truth by Jack Avis in More Self-Working Card Tricks by Karl Fulves (1984)