In past hunts for leakers, misplaced reliance on polygraphs has caused serious harm. In 1982, a polygraph dragnet for the source of a leak in the 30-member Defense Resources Board failed to find the leaker, but did lead to John Tillson, director of manpower management at the Pentagon being falsely accused. He was exonerated only when reporter George Wilson of the Washington Post assured Secretary of Defense Caspar Weinberger that Tillson was not the leaker. Polygraph hunts for leakers also led to Marine colonel Robert McFarlane (1982) and Assistant Undersecretary of Defense Michael Pillsbury (1986) being falsely accused.
On the other hand, polygraph "tests" have no scientific basis and are easily beaten through the use of simple countermeasures that polygraphers cannot detect. For information on how to beat the polygraph (you don't have to go to spy school), see AntiPolygraph.org's free e-book, The Lie Behind the Lie Detector (1 mb PDF):
http://antipolygraph.org/lie-behind-the-lie-detector.pdf
