AS JEREMY Kyle guests have found out to their cost, it’s not easy to beat the lie detector test.

Many have protested their innocence after the machine has found them guilty and, while they are not 100 percent accurate, they are said to have a high accuracy level.

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But if you find yourself in the Jezza detector chair, there is one simple way to beat the test – according to an expert.

Former policeman Doug Williams trained in using a polygraph after joining the police force in Oklahoma in 1972.

He became a certified expert in lie detectors but soon decided to try and work out if he could cheat the test – which measures signs of stress including raised blood pressure, heart rate and galvanic skin response (GSR).

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He told radio show This American Life: "I began to have doubts in 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.

“It wasn't until my friend came in and started talking about the pucker factor and tightening up the anal sphincter muscle when he was under stress.”

It turns out that clenching your bottom is the simple trick to duping the machine.

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Doug said: “After he left, I just hooked myself up to the polygraph test and tightened up my anal sphincter muscle like I was trying to stop my bowel movements and low and behold there was the most gigantic, wonderful, naturally occurring cardio rise, accompanying a GSR rise.”

Unfortunately, Doug went on to set up a site called Polygraph.com and ended up being prosecuted for obstruction of justice for sharing this information.

But he sums up his theory nicely: “It takes an a-hole with a little training to beat an a-hole with a little training.”

Guests on Jeremy Kyle frequently claim the lie detector results are wrong with one dad claiming his life had been torn apart by the test, after it appeared to prove he had cheated.

These are the top ten lie detector shockers from the show.