Glitch reported in popular polygraph can skew results, polygraphers say
WASHINGTON -- 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 learned.
As a result, innocent people might have been labeled criminal suspects, faced greater scrutiny while on probation or lost out on jobs. Or spies and criminals might 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 polygraphs 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. For federal jobs alone, more than 70,000 people are polygraphed each year, and most can't challenge the results in court or allege abusive tactics. While supporters say accuracy can be 85 to 95 percent, polygraphs aren't required to meet any independent testing standards to verify the accuracy of their measurements, unlike medical or other computerized equipment.
The concerns about the LX4000 add to the criticism.
"I'm astounded that a government agency would rely on this machine to make any decision," said John Stauffer, a Chicago accountant who was denied an FBI job in 2011 because he didn't pass his polygraph test. "I've always known that I shouldn't have failed. Now, I wonder whether this was the problem."
Scientists have experimented for more than a century with running a minuscule amount of electricity through sweat glands in the fingertips as a way to gauge emotions and mental effort.
The LX4000 measures sweat in two ways. One method, known as the manual mode, directly measures the secretions from sweat glands, as scientists historically have done. The other, known as the automatic mode, electronically filters the measurements and makes them easier to interpret.
David Reisinger, a veteran federal polygrapher, said he first witnessed a problem with the LX4000 in 2005. When he switched between the two modes, he noticed a difference in the measurements, said Reisinger, a polygrapher at the Defense Intelligence Agency at the time.
The Air Force's Office of Special Investigations noticed a problem in 2002, the year the LX4000 hit the market. When told of the problem, Lafayette officials "recommended that all polygraph charts be collected in the manual mode," agency spokeswoman Linda Card said in a statement.
Lafayette described the problem to the Defense Intelligence Agency as "minor" and repairable.
"We certainly agree that this is an issue that needs to be resolved," then-Lafayette operations manager Mark Lane told DIA officials in an email in 2007.
Tish Wells, Emma Kantrowitz and Kevin G. Hall contributed to this article.
This story was originally published May 27, 2013 at 9:40 PM.