Polygraphs are also used to varying degrees for screening job candidates in the public and private sectors, and in both private and criminal investigations. Polygraphs are such familiar instruments that few question the validity or efficacy of polygraph testing. The US Department of Energy administered it to American physicist Wen Ho Lee when first accusing him of leaking nuclear secrets to the Chinese. He passed the test, but the FBI subsequently reviewed the same test results and declared Lee a liar. Convicted spy Aldrich Ames passed numerous polygraph examinations over the years, while he was also passing CIA secrets to Russia.
Data is hard to come by.
The false positive rate could be anywhere from one percent to 20 percent. The National Research Council recently convened a panel on polygraphs to try to settle the matter, but its report is not expected until at least the end of 2001. According to critics, it lies not in the hardware, but in the interpretation of the test results. Using a polygraph as a lie detector involves studying a subject's physical response to specific questions. The series of questions asked usually starts with queries unrelated to whatever matter is being investigated in order to establish a baseline of physical reading, including blood pressure, sweat gland activity and breathing.