This column examines the use of two technologies in lie detection. "Brain fingerprinting" is based on the finding that the brain generates a unique brain-wave pattern when a person encounters a familiar stimulus. Use of functional magnetic resonance imaging in lie detection derives from studies suggesting that persons asked to lie show different patterns of brain activity than they do when being truthful. Issues related to the use of such evidence in courts are discussed. The author concludes that neither approach is currently supported by enough data regarding its accuracy in detecting deception to warrant use in court.