“Polygraphs Don’t Give True Story”

Noah Schachtman reports for Wired News. Excerpt:

The military may have ways — gruesome ways — of making people talk, as the Abu Ghraib prison scandal has shown. But it still doesn’t have a reliable method for figuring out whether those people are telling the truth or not.

Nearly 75 years since the introduction of the polygraph, there’s still nothing close to a foolproof lie detector. Traditional methods for catching a fibber have been battered by scientific study. And, despite endless waves of hype, the high-tech alternatives — brain scans, thermal images and voice analysis — have withered under scrutiny, or remain largely unproven.

“Everybody would love to have a lie detector that works. But wanting it isn’t going to make it happen,” said Stephen Kosslyn, a Harvard University professor of psychology.

“You can flip a coin, and get the same results,” said Mike Ritz, a former Army interrogator who now trains people to withstand questioning.

In a 2002 report, the National Academy of Sciences concluded that traditional polygraph screening was so flawed that it “presents a danger to national security.” The group found that too many innocent people who took polygraphs were labeled guilty, and too many guilty people slid by undetected.

Federal and local governments have carried on with polygraphs anyway. U.S. military investigators, armed with the devices, have been deployed to Iraq, to question candidates for detention. The Energy and Defense departments give out thousands of the tests every year to filter out potential security threats. And the Supreme Court has ruled that it’s up to the states to decide whether evidence from lie detectors is admissible in court.

Polygraphers contend that — especially when they start out with a piece of damning evidence — they can catch liars at rates of 90 percent or better. The problem is that polygraphs check only for physical responses that indicate deceit: heavy breathing, high pulse rate, sweat. But panting or sweating don’t necessarily mean that a person is guilty of anything. All these responses indicate is that someone is anxious, said University of Arizona psychology professor John JB Allen. And innocent people get jumpy, too — especially when there’s a bull-necked interrogator in the room.

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