Over the past few weeks, federal agencies have stepped up efforts to find potential leakers, such as the FBI, the Department of Homeland Security and the Department of Defense, are turning to lie detectors to help with searches.

On Tuesday, the FBI confirmed to NPR that it has started using polygraph tests to track employees who may be leaking information to the media.

When asked about the use of a lie detector exam, Tricia McLaughlin, Assistant Secretary for Public Affairs of the Department of Homeland Security, said in a statement: "DHS is the National Security Agency. We can, should, and we will conduct lie detector personnel."

McLaughlin added that the alleged leaker will be "prosecuted to the maximum extent of the law."

"In carrying out this investigation, the use of a polygraph will comply with applicable laws and policies," referring to an ongoing investigation into unauthorized national security disclosures, said in a memorandum last month. DOD has not confirmed whether the polygraph test has been conducted so far.

Poly detector tests have long played a role in criminal investigations, safety permits and pre-employment screening, but their reliability and accuracy have been the subject of debate.

This is something to know.

What is a polygraph test?

The modern lie detector was invented by a policeman in Berkeley, California over a century ago. The police officer John Larson was psychologist William M.

The lie detector was later perfected by another Berkeley policeman, Leonard Keeler, and quickly spread to police departments across the country.

Although the lie detector was originally called a machine that could tell the truth of a person, today, lie detector inspectors say that exams should not be synonymous with the “Lie-deetector test.”

"The lie detector found no lies," said Thomas Mauriello, a former agent for the Ministry of Defense.

"When we perceive a threat, a physical or a psychological threat, our physiological learning changes, and the lie detector will find those changes in the body," he added.

The test looks for changes in a person's heart rate, blood pressure, breathing and sweat activity - the reason is that lying can increase the response to fighting or flying. But for decades, Studies have shown that lie detectors may be inconsistent and are not suitable tools for evaluating authenticity.

Maurillo, a senior lecturer at the University of Maryland, said that in his experience, people’s sympathy nervous system can be deceived for many reasons.

"When you see the reaction, it doesn't necessarily mean they're lying," he added.

How they work

Alan Saqueella said the polygraph test usually requires three parts, and he is a certified polygraph inspector and professor at Embry-Riddle Aeronautical University.

The first is pretesting, where the examiner collects information from the subject. Then, there was a practical test that included about twelve questions, paused for a moment before the respondent answered. Finally, there was a post-test when respondents had the opportunity to discuss some of their results.

Saqueella said it is natural for people to feel anxious during exams, but examiners take steps to relieve tension, such as providing a list of questions in advance and starting with simple, harmless questions.

“Everyone is nervous even in pretest interviews,” he said. “What we are looking for is the deviation from that norm.”

Although police and federal agents use polygraph tests, most private employers in the United States are not allowed to test employees under federal law. Normally, testing is not accepted in federal courts.

Should I use a polygraph to investigate a leak? Expert weight

Saqueella, who performed a lie detector test on police candidates and lawyers, said the exam could be a useful investigative tool, but they shouldn't be "going all out." He also warned that the use of the test was too extensive to warn federal agencies.

"One person, you don't have resources, you don't make sense, and when you pull people randomly, it's definitely bad for morale."

Maurillo said the technology could be a beneficial step in the investigation, but stressing that lie detectors are most effective, rather than detecting lies, triggering someone to admit or disclose information.

“I have more people admit things before I put the attachment on it,” he said. “Sometimes people go and do a lie detector and they have something they don’t want to talk about and eventually they talk about it.”