Brain-wave scanners.

Brain-wave scanners are used to map activity in the brain. The patterns seen in the three-dimensional images produced by brain-wave scanning are indicative of whether or not a person is lying. The images are formed using magnetic resonance imaging (MRI). When experts examine the images to determine which areas of a person’s brain become active in response to questions, pictures, or other stimuli, this method is referred to as functional magnetic resonance imaging (fMRI). The subject is placed inside the scanning machine and allowed to interact with a computer screen to answer specific questions related to a crime. The MRI machine is interfaced with special computer software that recognizes specific brain patterns. When a person is telling a lie, the brain has to expend more energy than it does when the person is telling the truth. Even when a lie has been rehearsed in the mind of the subject, the subject uses more brain energy to think beyond the truth and access the lie. The extra brain activity shows up as a “bright” region on the brain-scanned image. In tested case studies, the fMRI method has shown an accuracy of more than 90 percent in detecting lies.