Perspective: Running Rings around Lies; A Major Insurance Company Has Recently Revealed Plans to Use Telephone Lie Detectors in an Attempt to Clamp Down on Fraudulent Claims. but What Exactly Does a Lie Detector Test Involve and Can the Results Be Trusted? Ross Reyburn and Claire Hills Speak to Scientists to Find Out

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Byline: Ross Reyburn and Claire Hills

Guilty-looking suspects wired up and under pressure is how cinema portrays the lie detector test.

Whether it's Sharon Stone remaining cool under lie detector pressure in Basic Instinct or Robert De Niro hooking a nervous Ben Stiller up to a machine in Meet The Parents, the test appears torturous for the non-guilty and easy to rig for the dishonest.

But now many more of us face having our untruths uncovered after a British company, Highway Insurance, admitted it was preparing to use telephone lie detector tests to help filter false claimants out of the system. But how effective are they?

The proper name for this sort of lie detection is a polygraph test. In fact, contrary to popular belief, the term lie detector test is incorrect.

'The polygraph does not detect lies - it measures the arousal which may be the result of lying,' declares Dr Keith Ashcroft, an Edinburgh-based forensic scientist.

The term polygraph means, literally, many writings and relates to the way the machine measures changes that take place in the body. These include sweating in the palms, blood pressure and respiration, which is measured using sensors placed around the chest and/or the abdomen. The test also measures blood flow, normally through a finger.

Individuals taking a polygraph test are normally asked a series of comparison question tests to assess their reactions to two different types of questions. One type would be a relevant question such as: 'Did you rob the bank?' The other would be one such as: 'Before the age of 20 did you ever lie to get yourself out of trouble?'

The theory is that guilty people will produce a larger response to the relevant question than those who are innocent, Ashcroft says. So their palms would probably sweat more than their innocent counterparts.

Once the interrogation is over the results can be fully analysed. Research has shown the test to be very accurate at pin-pointing truth-tellers from deceivers, he believes. 'It is about 90 per cent accurate in detecting people who are lying,' he says.

The results can be analysed either manually or by using a computer. The latter provides the most accurate results, according to Ashcroft. 'The electronics are contained within a small unit, attached to the computer,' he explains. The sensors which monitor sweat and breathing levels, heart rate, body movement and blood pressure are all connected to the box.

Computer technology allows complex techniques to be used to assess the results. Computer analysis is much more accurate than assessments done by people as computers can store more information. Another benefit is that it takes far less time for an accurate result to be obtained.

But the type of test set to be used by Highway Insurance differs from traditional methods as it concentrates solely on the voice. 'Features of language you can look at include changes in the voice pitch, but there is no hard scientific proof that it is indicative of lying,' Ashcroft warns.

He is currently researching the technology in conjunction with Dr Hans-Georg Rill of Johannes Gutenberg University in Maniz, Germany. They are attempting to find out exactly how reliable results from tests conducted over the telephone can be.

Mr David Alexander, the fraud investigation partner for business consultants KPMG in Birmingham, doesn't view lie detectors as having a future here.

'I haven't come across lie detectors being used by British companies,' he said. …