Symposium: 'Will brain imaging be lie detector test of the future?'

For almost a century, one of the staples of crime stories has been the wires, cuffs, and jiggling recording needle of the polygraph machine. In its time, the "lie detector" was hailed as a way to measure the telltale physiological signs of deception, including hard breathing, high blood pressure, and excess perspiration.

But in truth, the polygraph was never very accurate, hitting the mark only about 85 percent of the time - and meanwhile creating a lot of "false positives." As many as 25 percent of people telling the truth during a polygraph exam come out looking like liars.

In most federal courtrooms, polygraphs have not been admissible as evidence since 1923. Many businesses avoid them in personnel screening because of unreliable results - and because of protections afforded by federal law, in the 1988 Employee Polygraph Protection Act.

A 2003 report by the National Research Council (NRC) seemed to seal the doom of this old technology, flatly concluding that the polygraph was bad science and needed replacing.

Despite the wavering faith in polygraphs, insurance companies, government and law enforcement agencies, and others still do about 40,000 of the exams a year in the United States. And interest in a technology that catches liars has been heightened by the current war on terror.