Later On

A blog written for those whose interests more or less match mine.

Never agree to a polygraph (lie-detector) test

with 2 comments

First, it’s been found that agencies use the occasion of the test to ask completely inappropriate and prying questions. Second, and perhaps more important, the tests often give false results. Marisa Taylor reports for McClatchy:

Police departments and federal agencies across the country are using a type of polygraph despite evidence of a technical problem that could label truthful people as liars or the guilty as innocent, McClatchy has found.

As a result, innocent people might have been labeled criminal suspects, faced greater scrutiny while on probation or lost out on jobs. Or, just as alarming, spies and criminals may have escaped detection.

The technical glitch produced errors in the computerized measurements of sweat in one of the most popular polygraphs, the LX4000. Although polygraphers first noticed the problem a decade ago, many government agencies hadn’t known about the risk of inaccurate measurements until McClatchy recently raised questions about it.

The manufacturer, Lafayette Instrument Co. Inc., described the phenomenon as “occasional” and “minor,” but it couldn’t say exactly how often it occurs. Even after one federal agency became concerned and stopped using the measurement and a veteran polygrapher at another witnessed it repeatedly change test results, the extent and the source of the problem weren’t independently studied nor openly debated. In the meantime, tens of thousands of Americans were polygraphed on the LX4000.

The controversy casts new doubt on the reliability and usefulness of polygraphs, which are popularly known as lie detectors and whose tests are banned for use as evidence by most U.S. courts. Scientists have long questioned whether polygraphers can accurately identify liars by interpreting measurements of blood pressure, sweat activity and respiration. But polygraphers themselves say they rely on the measurements to be accurate for their daily, high-stakes decisions about people’s lives.

“We’re talking about using a procedure that has a very weak scientific foundation and making it worse,” said William Iacono, a University of Minnesota psychology professor who’s researched polygraph testing. “I already don’t have very much confidence in how government agencies conduct these tests. Now, they might as well be flipping a coin.”

Despite the scientific skepticism, intelligence and law enforcement agencies see polygraph as useful in obtaining confessions to wrongdoing that wouldn’t otherwise be uncovered. Fifteen federal agencies and many police departments across the country rely on polygraph testing to help make hiring or firing decisions. Sex offenders and other felons often undergo testing to comply with probation or court-ordered psychological treatment. Police detectives and prosecutors rule out criminal suspects who pass and scrutinize those who don’t.

In its ongoing series about polygraph use by government agencies, McClatchy found that such testing has flourished despite being banned for use by most private employers 25 years ago. . .

Continue reading. It’s a long article, and the lack of cooperation from Federal agencies, plus the company’s completely ignoring reports of the problem, are troubling.

My own feeling is that, if a job requires a polygraph test, get a different job. (Easier said than done, I realize, but it’s worth some effort to avoid the false charges and life-changing effects of a false polygraph result.)

Written by LeisureGuy

20 May 2013 at 9:01 am

Posted in Government, Technology

2 Responses

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  1. Problems with lie detector tests were known – and proven – long before the McClatchy report. One of the TV stations in San Francisco did an investigative report on lie detector tests. They took two groups of people and subjected them to lie detector tests, conducted by a trained professional. One group lied during the test and the other group told the truth. Of the group that lied, half were found to be lying, the other half were found to be telling the truth. The results were the same for the group that told the truth. A 50 percent accuracy rate is terrible. Fifty percent is a failing grade, an F on the test.

    That was about 20 or 25 years ago, if I recall correctly. Although technology has advanced since then, the metrics used by lie detector tests have not changed all that much.


    20 May 2013 at 1:06 pm

  2. Yes, I’ve known for years that lie detectors are unreliable. What I don’t understand is why their use is not illegal. A prescription drug would never be approved if it failed 50% of the time, obviously; the results of the outcome of a lie detector test are too serious to allow such an unreliable instrument.


    20 May 2013 at 1:49 pm

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