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October 8, 2002
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CMU prof finds polygraphs don't tell whole truth

Tuesday, October 08, 2002

By Byron Spice, Post-Gazette Science Editor

Tens of thousands of federal employees and job applicants undergo lie detector tests each year, but a scientific panel says polygraph testing is not a good way to find spies or other security risks.

In studies of specific incidents, lie detector results "are better than chance, but well below perfection," said Stephen Fienberg, a Carnegie Mellon University statistician who headed the National Research Council polygraph study.

That level of accuracy might be useful when investigating a crime. But using such an unreliable test for screening thousands of people risks misidentifying thousands of law-abiding people as potential security risks. Perhaps more importantly, from a security standpoint, most spies will escape the test undetected.

But agencies seem to overestimate the reliability of the test and so, when an employee passes the test, it is assumed that the employee is not a threat. "This overconfidence can create a false sense of security," Fienberg added.

The panel did not say that polygraphs should not be used by agencies, but warned that they should be used carefully. Unfortunately, no technical alternative to the existing polygraph exists, and the panel suggested the federal government begin sponsoring research to improve lie detection techniques.


More details in tomorrow's Pittsburgh Post-Gazette.

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