Lie detector expert names one thing criminal suspects do that shows they're guilty

A lie detector expert has said there's one thing suspects do which gives them away under examination.

Evy Poumpouras is a former US Secret Service agent who has worked as a polygraph examiner, but there's something she's found gives a suspect away as as guilty before they even take a test.

She appeared on the Diary of a CEO podcast to talk about 'the best liar I ever met', a man who had been caught putting skimmer devices on cash machines to nab the card details of people who tried to use it.

Describing him as 'a very low-level basic criminal', he was nevertheless the best liar she ever encountered.

Even when presented with a photo of him putting a skimmer device into a cash machine, which really ought to have meant he was caught bang to rights, but he remained unfazed.

Evy Poumpouras is a polygraph expert who has worked on lie detector tests. (The Diary Of A CEO/YouTube)

However, he did make the slip up of being 'overly co-operative' as apparently trying too hard to answer questions is a 'red flag'.

Despite this, what really alerted Poumpouras to his guilt was one thing the lie detector expert said she saw many guilty people do.

She said: "He said this a lot – ‘I swear to God, God is my witness, God knows that's not me.’

"We would call it divine intervention. Whenever you'd hear somebody do that, you knew it's like okay there was a problem.

"Why do you need God to come in to vouch for you? We actually have people come in with Bibles or rosary-beads.

"Whenever you saw that in the waiting room, I would say ‘Don't even polygraph them, they did it’."

However, she also added that it didn't necessarily mean that people were 'always lying' when they did this.

Of course, lie detectors are not accurate devices and their results are generally not admissible in court.

It has been documented that people who have been proven to be lying were able to pass the test, while in other cases people have told the honest truth and the detector has claimed they were speaking falsely.

In the UK information from a lie detector test cannot be used in criminal courts as evidence against someone who has taken the test.

Across the pond in the US the results of a lie detector test are generally not admissible in court unless both parties agree to it.

There are all sorts of tricks and tells to catch someone out in a lie, but even if someone is sending out what seems like obvious signs of dishonesty it's best to rely on proper, verifiable proof.