Christopher Talbot thought he would make a great police officer. He was 29 years old, fit, and had a clean background record. Talbot had military experience, including a tour of Iraq as a US Marine, and his commanding officer had written him a glowing recommendation. In 2014, armed with an associate degree in criminal justice, he felt ready to apply to become an officer with the New Haven Police Department, in his home state of Connecticut.

Talbot sailed through the department’s rigorous physical and mental tests, passing speed and agility trials and a written examination—but there was one final test. Like thousands of other law enforcement, fire, paramedic, and federal agencies across the country, the New Haven Police Department insists that each applicant take an assessment that has been rejected by almost every scientific authority: the polygraph test.

Commonly known as lie detectors, polygraphs are virtually unused in civilian life. They’re largely inadmissible in court and it’s illegal for most private companies to consult them. Over the past century, scientists have debunked the polygraph, proving again and again that the test can’t reliably distinguish truth from falsehood. At best, it is a roll of the dice; at worst, it’s a vessel for test administrators to project their own beliefs.

Yet Talbot’s test was no different from the millions of others conducted annually across the public sector, where the polygraph is commonly used as a last-ditch effort to weed out unsuitable candidates. Hiring managers will ask a range of questions about minor crimes, like marijuana use and vandalism, and major infractions, like kidnapping, child abuse, terrorism, and bestiality. Using a polygraph, these departments believe, increases the likelihood of obtaining facts that potential recruits might prefer not to reveal. And like hundreds of thousands of job candidates each year, Talbot was judged to have lied on the test. He failed.

New Haven allows failed applicants to plead their case in public before the Board of Police Commissioners. So in February 2014, Talbot sat down and recited his experiences with lie detectors. He had first applied to the Connecticut State Police and was failed for deception about occasional marijuana use as a minor. He then tried again with a police department in New Britain, where a polygraph test showed him lying about his criminal and sexual history.

This time he had failed the New Haven polygraph for something cryptically called “inconsistencies.” “[But] I’m not hiding anything,” he said at the hearing. “I was being straight and honest and I’ve never been in trouble with the law. I’m not lying about anything.”

Electronic lie detection is a peculiarly American obsession. No other country carries out anywhere near the estimated 2.5 million polygraph tests conducted in the US every year, a system that fuels a thriving $2 billion industry. A survey by the Bureau of Justice Statistics from 2007 found that around three-quarters of urban sheriff and police departments use polygraphs when hiring. Each test can cost $700 or more. Apply to become a police officer, trooper, firefighter, or paramedic today, and there is a good chance you will find yourself connected to a machine little changed since the 1950s, subject to the judgment of an examiner with just a few weeks’ pseudoscientific training.

Last week the technology burst into the news when Christine Blasey Ford, the woman who accuses Supreme Court nominee Brett Kavanaugh of sexually assaulting her as a teenager, said that she had taken a privately administered polygraph test to help bolster her account of the incident. “While not admissible in court, they’re used by various governmental agencies and many people believe in their abilities,” Douglas Wigdor, a former prosecutor who now represents victims in sexual harassment and sexual assault cases against high-profile men, told The Washington Post.