Lie detector test, also referred to as deception detection or polygraph test, is used to record physiological functions to ascertain truth and falsehood in response. It is commonly used by law enforcement around the world.

The authorities have found other uses for polygraph, though its evidence is generally not admissible in criminal court in the US and most of Europe.

In the UK, probation officers use lie detector test to monitor serious sex offenders, which have resulted in dozens of people returning to jail. In the US, the machines are used to screen candidates for the CIA and other government jobs.

“They are extremely helpful in focusing exams. It’s a quick and easy way to bring in a suspect and decide if we need to look more into that person or if we need to look for someone else in our investigation,” said Walt Goodson the president of the American Polygraph Association.

Goodson then emphasizes the usefulness of polygraph machines in conducting police investigations after spending 25 years in the Texas State Police.

According to research, these machines do detect dishonesty better than chance, but with significant error rates.

Even though, the accuracy of the polygraph machine has been speculated over for a long time, its biggest flaw is the point that an honest person may be nervous – and a dishonest person may be non-anxious.

Doug Williams, certified expert in lie detector tests, has a say on how to beat a lie detector test.

In 1972, he joined the police force in Oklahoma so going to polygraph school is part of their training. As time passed, he began to tire of the process and begin to wonder exactly how effective the tests were.

“I began to doubt the tests after a while, I knew I could control my breathing but I didn’t know for sure how to control the cardio and the blood pressure,” Williams’s revelation to radio show, ‘This American Life’.

“It wasn’t until my friend came in and told me about the ruck up factor and tightening up the anal sphincter muscle when he was under stress, Williams added”

While it is very kind of Williams to share this information with the world, his honesty actually got him sued for obstruction of justice and mail fraud.

Watch the video below and examine how to beat a lie detector test.

Sources: Mirror, BBC