“Telling the Truth About Lie Detectors”

Dan Vergano reports for USA Today. Excerpt:

A long-time law enforcement favorite, the lie detector, now finds itself sweating the hot lights of scientific inquiry.

Crime dramas have long depicted the polygraph’s tangle of wires and wiggling chart lines uncovering lies during a hard-boiled criminal interrogation. As suspects are questioned, the device checks for sweaty skin or racing hearts to root out deception, but the machine’s accuracy has long been in dispute.

Nonetheless, the polygraph has a higher-than-ever profile. It’s an ongoing bone of contention on Capitol Hill and a factor in recent spy investigations of FBI turncoat Robert Hanssen and physicist Wen Ho Lee. In the Lee case, the FBI’s contention the physicist had lied on a polygraph test in 1998 led to 59 charges, all but one dropped in a plea bargain two years later. That sparked a request for a National Academy of Sciences (NAS) report, due as soon as the first week of October, on the validity of the polygraph.

Now, some of the same politicians who called for polygraphs of federal employees are involved in an FBI investigation aimed at finding who’s responsible for a classified intelligence leak about two intercepted messages that hinted at the Sept. 11 terrorist attacks. Many House-Senate intelligence committee staffers and legislators, perhaps most prominently Sen. Richard Shelby, R.-Ala., have declined to take polygraph tests.

“Allowing the executive branch to submit the legislative branch to lie-detector tests raises constitutional issues of separation of powers,” Shelby says, in a statement.

Polygraph critics such as Alan Zelicoff of Sandia National Laboratory in New Mexico find the sensitivity of Shelby and his committee peers ironic, noting two years ago that the committee helped instigate the polygraph screening of weapons scientists designed to root out spies.

A physician biodefense researcher at the weapons lab, Zelicoff has led opposition to the polygraph there, saying that for screening purposes, the device’s measures — pulse, blood pressure, breathing and sweating — reveal deception about as well as a coin flip. He likens the polygraph to a defective medical test, one whose high false-positive rate, depicting honest people as liars, makes it unreliable as a diagnostic tool. Last year, Attorney General John Ashcroft estimated the false-positive rate of polygraphs at 15%, about a one-in-six chance, at a news conference.

Polygraphs are perhaps the most controversial tool in law enforcement. Some states and federal court judges now accept lie-detector results, but many states ban them outright. A 1998 Supreme Court decision allowed such bans, but read in part, “There is simply no consensus that polygraph evidence is reliable: The scientific community and the state and federal courts are extremely polarized on the matter.”

The disagreements have become so entrenched that the NAS deliberately sought members for its report committee who had never staked out a position on the issue. “My primary qualification is I’ve never worked on the topic,” noted committee chair Stephen Fienberg, a statistics expert at Carnegie Mellon University in Pittsburgh.

The key question before his committee is whether the lie-detector test is a scientific test of deception.

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