In the eyes of federal prosecutors in Virginia, Chad Dixon is a brazen criminal whose misdeeds threatened border security, state secrets and young children across America. They say he taught convicted sex offenders and aspiring federal law enforcement officers how to cheat their court- or job-imposed lie detector tests — even when he knew that they planned to use his advice for nefarious purposes.

In the eyes of his supporters, though, Dixon is no more than an electrical worker who did some Internet research on polygraph testing. And for offering instructions sometimes as simple as “relax and breathe normally,” he probably will end up in federal prison.

Dixon, 34, of Indiana, pleaded guilty in December to wire fraud and obstruction of an agency proceeding and is scheduled to be sentenced Friday in federal district court in Alexandria. He is accused of teaching what prosecutors term “polygraph countermeasures” to as many as 100 people across the country — among them convicted sex offenders in the Washington area and undercover agents who told Dixon that they would use his techniques to cheat their tests for Customs and Border Protection jobs.

The case has reenergized a national debate on the accuracy of polygraph testing and led to some speculation that federal authorities intend to prosecute those spreading information on how to trick lie detectors. The McClatchy news organization reported last month that Dixon’s case was part of a broader federal effort to discourage possible criminals and spies from getting government jobs using polygraph countermeasures.

Although Dixon appears to be the first charged publicly, others offering similar instruction say they fear they might be next.

“I’ve been worried about that, and the more this comes about, the more worried I am,” said Doug Williams, a former police polygraphist in Oklahoma who claims to be able to teach people to beat what he now considers a “scam” test.

In court filings, prosecutors said Dixon developed his polygraph countermeasures largely based on materials he took from Williams’s Web site. Williams — who declined to comment on Dixon’s case specifically — has written books and appeared on national television programs criticizing lie detectors and telling people how to beat them.

Teaching about the flaws of polygraph testing is not inherently illegal. The test monitors a variety of physical responses — such as breathing and heart rate — and Williams and others preach that you can manipulate it by artificially provoking a physical reaction when you’re supposed to and keeping your reactions in check when you’re not.

Whether the measures are effective is a matter of debate. Barry Cushman, president of the American Polygraph Association, said hands-on training, with feedback, on countermeasures has been shown to work sometimes in laboratory settings. But mere instruction, video or written, is unlikely to succeed, he said.

Dixon was charged after he helped undercover agents learn to cheat the test after they told him specifically that they intended to lie as they applied for federal jobs. Nina J. Ginsberg, Dixon’s attorney, wrote in court filings that much of what Dixon did was legal and that prosecutors were using “hyperbole” in describing his crimes.

“While understandably unpopular with law enforcement and other government agencies, polygraph countermeasures training is widely available and unless the person providing the training knows that the countermeasures training will be used to commit a criminal offense . . . it is protected First Amendment speech,” Ginsberg wrote. “Like it or not, providing polygraph countermeasures training, even to the most despicable among us, is not a crime.”

Dixon declined to comment for this article.

According to prosecutors, Dixon charged his customers $1,000 a day or more for hands-on training, advertising on his “Polygraph Consultants of America” Web site that he could help people appear to be truthful on a test, then traveling across the country to meet those interested in his services. Among his 69 to 100 clients from late 2010 to April 2012, prosecutors said, were unqualified applicants for federal law enforcement jobs and convicted sex offenders — including a former English teacher at a middle school in Rockville who was convicted of sexually abusing a 12-year-old boy and had to take polygraph tests as a condition of his parole.

Perhaps the most outlandish examples of Dixon’s training, though, came when undercover federal agents approached him for his services in late 2011 and early 2012. When one agent posing as a Customs and Border Protection applicant told Dixon his brother was a member of the Zetas drug cartel involved in “drugs, extortion, murder [and] kidnappings” — and that he routinely let his brother use his identification — Dixon told him to reference the man only as a “distant relative” and say, “Look, I don’t really know what he’s into,” prosecutors wrote.

Ginsberg wrote in court filings that Dixon trained only between 50 and 70 people and that most of them were preparing for marital fidelity polygraphs. She estimated that there are at least 30 others offering services similar to Dixon’s and that none of them have been charged.

“Mr. Dixon has done nothing that warrants the government’s attempts to make him the poster child for its newly undertaken campaign to wipe out polygraph countermeasures training,” she wrote.

George Maschke, whose Web site offers similar information on the flaws of polygraph testing but does not offer hands-on training, said he was troubled by Dixon’s case.

“It seems to me that they’re going after critics of the polygraph and then fabricating a crime to prosecute where there had been no crime to prosecute before,” Maschke said. “Free speech is important, and I don't think explaining to people how the polygraph works, including its vulnerability to countermeasures, should be criminalized.”

Dixon, a father of four, wrote in a letter to the judge that he was “disgusted” with himself and that he did not realize initially that what he was doing was criminal. He wrote that some of his “countermeasures” were as simple as “to relax and breathe normally on relevant questions.”

“I was so dead set in my mind that this machine was bogus and I think this mind set made me feel that what I was doing wasn’t illegal and wasn’t that bad,” he wrote.

Prosecutors have asked that Dixon serve between 21 and 27 months in prison, though preferably at the “low end” of the range. His sentencing is scheduled for 9 a.m. Friday.