US News and World Report provides some background on the so-called “lie-detector.” Despite its use by over 20 federal agencies, polygraph “technology” (circa 1915) has never been proven to determine truth from deception with better than chance accuracy under field conditions. Excerpt:
Most U.S. courts ban their use as evidence. A federal law bars private firms from using them to screen job applicants. Even Attorney General John Ashcroft concedes they have a 15 percent error rate. Despite all this, the use of polygraphs is sharply expanding in the federal government. Over 20 federal agencies now use the “lie detector” for security, criminal investigation, and screening job seekers.
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“Junk science.” The concept is simple enough: A technician hooks monitors to one’s arm, fingers, and chest, which measure changes in the body’s pulse, temperature, respiration, and skin moisture. Polygraph operators say sharp fluctuations can be evidence of deception. Critics, however, brand the entire field “junk science” and claim that the best scientific studies show error rates of 40 percent or more. “It’s little better than flipping a coin,” says University of Minnesota psychologist David Lykken.