Lie detectors not good enough to detect spies, terrorists

Scripps Howard News Service
October 08, 2002

WASHINGTON - Lie detector tests are too unreliable to weed out spies or terrorists from prospective or current employees in sensitive jobs, according to a new report released Tuesday by the National Research Council.

"National security is too important to be left to such a blunt instrument," said Stephen Fienberg, a professor of statistics and computer science at Carnegie Mellon University in Pittsburgh and chairman of the committee that wrote the report in response to a request from the Department of Energy.

"The polygraph's serious limitations in employee security screening underscore the need to look more broadly for effective, alternative methods," he added.

The Energy Department asked the independent council, part of the National Academy of Sciences, to study the scientific validity and reliability of using polygraph testing to identify personnel who might jeopardize security in the wake of concerns about the theft of nuclear secrets from weapons labs several years ago.

Many researchers at facilities such as Sandia National Laboratory in New Mexico and Lawrence Livermore National Laboratory in California have complained bitterly about being required to take the tests when their reliability is so controversial.

Lie detectors measure breathing rates, heartbeat, blood pressure and other vital signs that are known to change when people are under stress, such as when they lie. But some people suppress those changes while others show anxiety even if they're telling the truth, the researchers noted.

And much of the research that's been done on the devices is of such poor scientific quality that it would not have met federal standards for funding, the panel said.

"Polygraph testing yields an unacceptable choice for DOE employee security screening between too many loyal employees judged deceptive and too many security threats left undetected," the report said. "It's accuracy in distinguishing actual or potential security violators from innocent test takers is insufficient to justify reliance on its use in employee security screening in federal agencies."

However, the committee said most people believe lie detectors are accurate, and that alone might deter some security risks from applying for sensitive jobs if they know they'll have to take the tests.

The DOE had no immediate response to the report.

Polygraphs are also widely employed by federal intelligence and law enforcement agencies. The CIA has used polygraphs routinely for years, but hundreds of agency employees claim their careers have been ruined with false results. The FBI has screened new applicants with the tests for several years, and has stepped up testing of current employees in sensitive posts as a result of the Robert Hanssen spy case. Hanssen, a former FBI agent, worked for years as a Soviet and Russian spy.

The committee distinguished the relative effectiveness of the polygraph in crime investigations, where subjects are asked questions about specific events, versus security screening where generic questions are posed. In criminal cases, the devices can tell the difference between lies and truth "at rates well above chance, although well below perfection."

Security screeners don't know what plans a spy might be hatching, or what minor misdeed a loyal employee might have done in the past that they might be anxious to conceal, the scientists said. Moreover, some highly motivated individuals can be physically trained to hide their physical responses during the tests.

Looking for one or two individuals who are real security risks out of tens of thousands "requires diagnostics of extremely high accuracy, beyond what can be expected from polygraph testing," the report said.

The scientists said some potential improvements or alternatives to polygraphs, such as computerized analysis of results and devices that measure facial expressions, voice quality, even brain activity, show promise, but none are yet ready to be deployed in security screening.

On the Net: www.nationalacademies.org

(Contact Lee Bowman at BowmanL(at)shns.com or online at http://www.shns.com)