Pentagon issues pocket lie detector to troops
David Edwards and Nick Juliano
Published: Wednesday April 9, 2008

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The Pentagon is planning to give US troops fighting in Iraq and Afghanistan "hand-held lie detectors" aimed at rooting out potential insurgents and terrorists. But polygraph experts doubt the system's accuracy and Defense Department memos show results of the few tests that were run were manipulated to demonstrate more success with them than was achieved, according to an MSNBC investigative reporter.

"The Defense Department says the portable device isn't perfect, but is accurate enough to save American lives by screening local police officers, interpreters and allied forces for access to U.S. military bases, and by helping narrow the list of suspects after a roadside bombing," MSNBC's Bill Dedman reports. "The device has already been tried in Iraq and is expected to be deployed there as well."

The Pentagon argues the portable polygraphs have accuracy rates up to 90 percent, but Dedman reports the military arrived at those figures by omitting some results from the tests. The Preliminary Credibility Assessment Screening System, or PCASS, uses a hand-held computer that analyzes readings from censors attached to an interviewees hand and wrist. The computer displays "Green" if it believes the person is honest, "Red" if they are being deceptive and "Yellow" if it is unsure.

The Pentagon, in a PowerPoint presentation released to through a Freedom of Information Act request, says the PCASS is 82 to 90 percent accurate. Those are the only accuracy numbers that were sent up the chain of command at the Pentagon before the device was approved.

But Pentagon studies obtained by show a more complicated picture: In calculating its accuracy, the scientists conducting the tests discarded the yellow screens, or inconclusive readings.

That practice was criticized in the 2003 National Academy study, which said the "inconclusives" have to be included to measure accuracy. If you take into account the yellow screens, the PCASS accuracy rate in the three Pentagon-funded tests drops to the level of 63 to 79 percent.

The portable lie-detectors are far less accurate than a typical polygraph, and the Pentagon documents Dedman cites show they are much less likely to give a definitive yes-or-no answer as to whether someone is being truthful. (A traditional polygraph gave uncertain responses 7.2 percent of the time, compared to 27 percent and 16 percent in tests with the PCASS.)

The Pentagon argues that the PCASS is better than nothing, but an expert on lie detector tests calls their approach wrong-headed.

"I don't understand how anybody could think that this is ready for deployment," statistics professor Stephen E. Fienberg, who headed a 2003 study by the National Academy of Sciences that found insufficient scientific evidence to support using polygraphs for national security, told MSNBC. "Sending these instruments into the field in Iraq and Afghanistan without serious scientific assessment, and for use by untrained personnel, is a mockery of what we advocated in our report."

This video is from MSNBC, broadcast April 9, 2008.