This is what it's like to have a lie detector test; The ECHO's Alan Weston finds out if you can REALLY cheat a polygraph test.
Lie detector tests are a favourite device of TV cop dramas and Hollywood movies - but what's it like to undergo one for real? And can they be cheated?
Having been subjected to one myself - purely for journalistic purposes, you understand - I can state that you would have to be a consummate liar to outwit one of these things.
Once hooked up for a polygraph test, you will be measured on four different physiological reactions: breathing pattern, heart rate, blood pressure, and sweat gland activity.
While the experience was painless, I wouldn't say it was relaxing either: it felt like something between a medical examination and being strapped into an electric chair.
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The expert who carried out the polygraph test, Dr Keith Ashcroft, showed me a sheet of paper with four numbers on it.
I had to add the figure '3' and circle it, using my non-dominant (in my case, left) hand. The reason for this is that I would remember doing it more clearly.
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He then asked me if I had written down all five numbers, to which I was required to answer 'no' each time. Clearly, in one case, this would be a lie.
I underwent the procedure, with the results being fed into Dr Ashcroft's laptop. Although I didn't feel any particular unease when I knowingly, and wrongly, stated 'no' to one of the questions, the results - as fed into the computer - revealed that this answer was false, with increased sweat gland activity, heart rate, and blood pressure.
In other words, you might think you're fooling the machine, but - more often than not - you will be betrayed by your unconscious physiological response when knowingly telling an untruth.
This simple preliminary procedure, known as an acquaintance test, assured Dr Ashcroft that I would be a suitable candidate for a full lie detector test, were he to carry one out.
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Dr Ashcroft, who trained as a forensic psychologist, travels the world to carry out these tests.
He can be called upon by everyone from defence lawyers, to those responsible for carrying out illegal drugs tests on athletes, to companies dealing with sensitive information, who want to be sure an actual or potential employee is trustworthy.
He said: "This could include a trawl of suspects in the case of a security breach.
"I can also assist in a criminal investigation, although it's important to point out that polygraph evidence is not evidence in and of itself. It's merely an indication as to whether that person should be investigated further."
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Dr Ashcroft, who prefers to be known as a "credibility assessment consultant", established hisCentre for Forensic Neurosciencein 2002.
Since then, he has contributed to a number of high-profile cases, including that ofMichael Shields- theLiverpoolfan jailed in 2005 after being wrongly convicted of attempted murder in Bulgaria, following the Reds' European Cup Final victory in Istanbul.
Mr Shields was initially jailed for 15 years in Bulgaria but was transferred to the UK in 2006 to serve the rest of his sentence - now cut to 10 years - in a British prison.
He was not freed until 2009 after being declared "morally and technically innocent."
The issue of lie-detector tests has been much in the news recently, after it was revealed high-risk domestic abuse offenders could face mandatory polygraph tests when released from prison.
It was part of a broad package of measures proposed by the Home Office as part of its domestic abuse bill.
The polygraph tests the subject's breathing pattern, heart rate, blood pressure, and sweat gland activity
You can't argue with the computer - the results of the polygraph test are fed into this programme and analysed
Dr Keith Ashcroft is a fully trained polygraph examiner
ECHO reporter Alan Weston is hooked up to the polygraph - let the lie detector test begin!
Michael Shields (200)