Doug Williams. The Way Back Machine A former Oklahoma police officer pleaded guilty on Thursday to obstruction of justice and mail fraud for teaching people how to pass lie-detector tests — even if they're lying, according to the Department of Justice.

Douglas Williams, 69, owned and operated Polygraph.com, a now defunct website that offered training to conceal information during lie-detector tests, also known as polygraphs.

Many of Williams' customers were required to undergo the tests for background checks, as part of federal investigations, and under the terms of their parole and/or probation, according to the indictment.

Williams touted his services on his website, per a January 20, 2013, cached version available on the Way Back Machine, an internet project that records website caches before they go offline:

Police polygraph expert, Doug Williams will get you properly prepared to pass your polygraph test. In fact, he is the only one who can get you properly prepared because he is the only one with authentic credentials, a technique that is tested and proven to be effective, and the demonstrated ability to teach you how to always pass your polygraph test — nervous or not — lying or not — no matter what!

Aside from DVDs and other instructional materials, Williams also offered in-person training that ran between $1,000 and $5,000 and instructed his customers to lie about receiving it, according to the indictment.

'Operation Lie Busters'

That's exactly how the feds nabbed Williams — through an investigation called "Operation Lie Busters," which involved undercover agents from Customs and Border Patrol, The Guardian reports. The sting was part of the Obama administration's push to stop federal leaks after former NSA contractor Edward Snowden's disclosures of classified information.

In October 2012, an undercover agent, claiming to be an inspector with the Department of Homeland Security, called Williams and said he was under investigation for allowing a friend to pass through customs with contraband, according to the indictment. Another undercover agent later said he had applied for a job with Border Patrol and "left stuff off his applications." In both cases, Williams received payment and met with the clients for training.

A screenshot from Williams' website, Polygraph.com. Screenshot/Wayback Machine

"I haven't lived this long and f----- the government this long, and done such a controversial thing that I do for this long, and got away with it without any trouble whatsoever, by being a dumbass," Williams told one of the agents, according to the indictment.

For decades, Williams marketed himself as a guerilla critic of the government's overreliance on polygraphs, which he considers massively inaccurate. His website claimed that over half of people who take lie detector tests fail simply because they're nervous.

"This indictment [was] brought simply to punish and silence me because I have the audacity to protest the use of the polygraph," he told NPR.

In 1986, Williams served as an expert source for a "60 Minutes" exposé in which CBS staged the theft of a camera and called a polygraph company to conduct an investigation. One of the test administrators identified an employee named Paul as the fake culprit because he was supposedly "deceptive" when answering questions.

Problems with polygraphs

Polygraphs work by monitoring three physical reactions: sweat, using electrodes attached to the fingers; heart rate and blood pressure through an arm cuff; and breathing through chest straps. Any changes in those factors cause needles making lines on a paper to rise and fall, clueing experts in to the subject's mindset.

A typical polygraph test. Flickr/Lwp Kommunikáció In 2002, however, the National Academy of Sciences published one of the most comprehensive studies of polygraph accuracy, concluding that while the tests could "differentiate lying from telling the truth at rates well above chance," they aren't accurate enough for security purposes. Polygraph supporters, however, such as the American Polygraph Association, actually embrace the study.

"That's still better than any other technology available today," the society's president, Raymond Nelson, told NPR. The association puts the test's accuracy above 80%.

The society, headquartered online at polygraph.org, has a counterpart in antipolygraph.org, which closely followed Williams' trial. One of the most visible statements on the site claims polygraphs have "no scientific basis," referring to a paper by University of Minnesota psychology professor William G. Iacono.

Regardless of the questions surrounding its accuracy, polygraph testing remains legal at federal and state levels. The Employee Polygraph Protection Act, however, does prohibit most private employers from using them during interview processes or employment.

With no sentencing date set, Williams faces up to 20 years in prison and a $250,000 fine, plus fees, for each count, totaling 100 years and more than $1.2 million.

"Lying, deception, and fraud cannot be allowed to influence the hiring of national-security and law-enforcement officials, particularly when it might affect the security of our borders," Assistant Attorney General Leslie Caldwell said in a statement. "[The] conviction sends a message that we pursue those who attempt to corrupt law enforcement wherever and however they may try to do so."

Williams' lawyer didn't immediately respond for comment.