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The inventions that could end the polygraph's long, imperfect run are not yet ready for wide use. Some of them, however, are getting tantalizingly close.
MAGNETIC RESONANCE IMAGING
No matter how cool your body is during questioning, your mind could still rat you out. Brains require blood to operate, and the harder they work, the more they need. Many regions of the cortex are thought to be recruited for a lie, but three stand out: the anterior (front) cingulate, which reconciles goals and intentions; the right orbital/ interior frontal, which processes the sense of reward; and the right middle frontal, which helps govern tasks requiring more than ordinary thought. Functional magnetic resonance imaging (fMRI) looks for such busy, well-oxygenated areas. Get a hit in all three zones, and you may have a liar. That is what No Lie MRI and Cephos claim they can do, with an accuracy of 90% to 93%.
ELECTROENCEPHALOGRAM
Blood flow isn't the only way your mind can blow your cover; electrical activity can too. Your brain emits signals called event-related potentials (ERPs) that can be tracked with a high-density electroencephalogram (EEG) machine and 128 sensors attached to the face and scalp. Telling the truth and then a lie can take from 40 to 60 milliseconds longer than telling two truths in a row, because the brain must shift its data-assembly strategies. In theory, if a subject truthfully answers a question related to intention (say, "Are you traveling to Miami?") and then answers a more relevant question about intention (say, "Do you plan to detonate a bomb?"), the ERP patterns might reveal if the answer is honest. Psychologists working on the technology believe it is 86% accurate.
EYE SCANS
The stress that creates the clues picked up by polygraphs also boosts blood flow in capillaries around the eye. A new application of thermal-imaging technology, called periorbital thermography, uses a high-resolution camera to detect temperature changes as small as .045°F (.025°C). Endocrinologist James Levine of the Mayo Clinic in Rochester, Minn., co-authored a paper in the journal Nature in 2002 in which he claimed a lie-detection accuracy of 73%. Investigators at the Department of Defense Polygraph Institute (DODPI) in Fort Jackson, S.C., tell TIME they have reached 84%.
Scientists at DODPI have also become expert at tracking the motion of the eyes. When the eye takes in a series of images of faces, objects or scenes, it spends less time on familiar elements because the brain needs less processing to interpret them. DODPI has developed an infrared camera that can track eye movement and an algorithm that can interpret it, providing clues as to whether a suspect recognizes, say, the face of a kidnapped child. Tests have reportedly achieved an 85% to 92% success rate.
MICROEXPRESSIONS