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Accuracy of Widely-Used Polygraph Machine Under Fire

In the hands of a skilled operator, such as the late John Reid of John E. Reid and Associates, one of the early pioneers in the lie detection field, the polygraph can be a useful tool. Reid, along with noted Northwestern Law School criminal law professor Fred Inbau, essentially originated and popularized the use of polygraph testing in Chicago.

Although Reid felt that a polygraph was accurate more often than not, he never lost sight of the fact that the key component of its usefulness was not just the machine itself, but the training and skill of the operator. As the technology evolved this focus on skill has decreased, with more and more law enforcement agencies and private organizations relying on what they hope is an increasingly reliable lie detection device. [See: PLN, Dec. 2008, p.1].

However, recent revelations have cast doubt on the accuracy of one of the most popular polygraph machines, the LX4000 manufactured by Lafayette Instrument Company.

An article published by McClatchy DC alleges that the LX4000, widely used by federal agencies like the FBI, among others, has some “glitches.” Apparently one of those glitches is in the computerized measurement of a person’s perspiration, which is one of the methods by which polygraph operators attempt to determine truthfulness. Although the manufacturer described the problem as “minor,” “rare” and “occasional,” others aren’t so sure.

From the very beginning, the use of polygraphs to determine truthfulness has been questioned by many scientists and criminologists who doubt that the interpretation of blood pressure, sweat and respiration alone can tell if a person is being deceptive. The news that one of the most widely-used polygraph machines has a technical problem that has gone unpublicized for years has only added to this skepticism.

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

Those who doubt the efficacy of lie detection devices feel that law enforcement and investigative agencies rely too heavily on polygraph tests to determine truthfulness and obtain confessions that might not be genuine. [See: PLN, Dec. 2011, p.14; April 2011, p.18]. Studies have shown that even innocent people can be conditioned to give false confessions, and the use of polygraphs as a tool of interrogation rather than a way to discover the truth would not have sat well with Reid.

He also would have been unhappy with the secrecy that surrounds the lie detection field, with government agencies citing national security or law enforcement concerns to justify the lack of transparency in their use of polygraphs. Around 73,000 people are polygraphed by the federal government every year, despite the fact that under a 1988 law such testing has been barred for most private-sector employers. Although lie detector operators claim an accuracy rate of 85-95%, polygraphs are not subject to standardized testing or calibration unlike medical or other computerized devices. Additionally, those denied jobs due to a “failed” polygraph test have no recourse in the courts.

At least 27 state and local agencies and 10 federal agencies either use or have used the LX4000, and many were surprised to learn about problems with the machine’s accuracy.

“If this was being debated, I would have liked to have known about it. I believe in polygraph 100 percent, but I want to make sure it’s working like it’s supposed to be working,” said Dan Fields, supervisor of the Kansas City, Missouri police department’s polygraph unit.

The issue with the LX4000 has to do with how it measures the minuscule amount of electricity produced by sweat glands in suspects’ fingertips as a means of detecting nervousness or tension, which are considered indications of deception by lie detector operators. This measurement can be done either in manual mode, which directly measures sweat secretions, or in automatic mode, which interprets the same electrical impulses based on a computer program and “smooths out” the results. Many operators have only used the automatic mode because it is easier to interpret. What they didn’t realize was that the data they were interpreting may have been incorrect.

One person who noticed inaccuracies produced by the automatic mode of the LX4000 was David Reisinger with the Defense Intelligence Agency (DIA), who reported the problem to the manufacturer a decade ago. Although Reisinger recommended that the DIA discontinue using the LX4000, the agency declined to do so. Additionally, the Air Force’s Office of Special Investigations informed the Lafayette Instrument Company as early as 2002 that there were problems when using the LX4000 on the automatic setting.

Lafayette countered by saying that all polygraph machines should be operated in the manual mode, but did not publicize the problems with the automatic setting. The company now markets the LX5000, which also has the possibly problematic automatic mode. Lafayette defended its products, arguing that the McClatchy DC article was based on “misinformation” and stating both the automatic and manual modes “have been shown to work satisfactorily,” though admitting there are “occasional differences.”

Charles R. Honts, a psychology professor at Boise State University who has studied polygraphs, was concerned not only with the manufacturer’s failure to correct or publicize the accuracy issues of the LX4000, but also with the human costs to those deemed to have “failed” a faulty lie detector test.

“The insidious thing is that this phenomenon biases tests against the innocent, and the government knows that. This is just another example of science being ignored,” he said.

Professor Iacono conducted his own tests of older Lafayette polygraph machines with fewer features that apparently relied more on the expertise of the operator, and concluded that some of the older machines were more accurate.

“Because of that, I have never criticized the actual [lie detector] measurements, and I’ve always thought they’ve only made them better,” he noted. “What this shows is that they’ve actually made them worse and they can’t fix the problem.”

Reid and Professor Inbau, who were both knowledgeable in police interrogation and investigation techniques, recognized that in the hands of an inexperienced or over-aggressive operator, polygraph machines can be abused and become a tool for injustice. In such cases, people accused of crimes – even if innocent – could produce polygraph responses deemed untruthful. In fact, Reid said that an observant lie detector operator could almost glean more from his questioning and personal observations of a suspect than from the polygraph results.

Perhaps that’s the reason why lie detector tests are not admissible in any court of law in the United States. That has not, however, discouraged law enforcement agencies from continuing to use polygraph examinations on a regular basis, despite questions about their accuracy and reliability.

In May 2014, the Drug Enforcement Administration agreed to pay $500,000 to settle a lawsuit filed by 14 contractors who provided translation services related to DEA wiretaps, who had been fired after failing lie detector tests. In addition to the monetary settlement, the agency agreed to re-screen the contractors without considering the polygraph results.

The suit alleged that the DEA didn’t have authority to require the contractors, who were employed by a private company, to take the lie detector tests. The company involved agreed to settle with five of the plaintiffs, with other claims still pending. See: M.G. v. Metropolitan Interpreters and Translators, Inc., U.S.D.C. (S.D. Cal.), Case No. 3:12-cv-00460-DMS-MDD.

At the time the contractors were required to undergo polygraph examinations, the DEA was using the LX4000 machine.

“The people who were involved in this case work hard and are of impeccable character,” said Gene Iredale, the attorney who represented the contractors. “But because of a squiggle on a piece of paper and the poor administration of these polygraphs, they were humiliated and unfairly deprived of their employment.”


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