The government's case for lie detectors has a glaring inconsistency

http://www.guardian.co.uk/commentisfree/2012/jul/23/lie-detectors-inconsistency-evidence

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The news that the government intends to carry out compulsory polygraph (lie detector) tests on sex offenders leaving prison carries more than a whiff of hypocrisy about it. If the offenders fail the test and the machine indicates they are lying (for example when asked questions relating to their lifestyle and sexual behaviour) they will be returned to prison.

Not much wrong with that, some may say; sex offenders wreak havoc in the lives of their victims and the public are entitled to be protected from them. And if lie detectors can assist in the safeguarding process, why not use them?

Because the system is wearing two faces; on the one, it will imprison those "found out" by the polygraph; on the other, it refuses to accept lie detector evidence from those claiming to be wrongfully convicted, who have passed polygraph tests with flying colours.

I am in regular correspondence with two men who claim to be victims of miscarriages of justice. Both agreed to take part in polygraph tests – at their own expense, and only after protracted wrangles with the Ministry of Justice. The MoJ does not welcome such applications from serving prisoners, despite their apparent wholehearted backing of the plans to force released offenders to take the same tests. Both men passed the tests.

Polygraph testing divides opinion sharply across the criminal justice board. Advocates of the system claim 90-95% success rates, while businesses who provide polygraph services go higher, claiming 95-100%. Polygraph testimony is admitted in court in only 19 states in the USA, subject to the discretion of the trial judge; but it is widely used by prosecutors, defence attorneys and law enforcement agencies across the country. Most European countries do not regard polygraph tests as reliable evidence. Usually, voluntary tests are undertaken by defendants, in an effort to show innocence.

In 2008, Gordon Brown proposed their use by the Benefits Agency to flush out fraudulent claims, but the plan was quietly dropped after pilot tests proved too costly. Pilots for the current testing plans were carried out on sex offenders by East and West Midlands probation staff from 2009 to 2011. Staff found offenders tested made twice as many admissions of unacceptable behaviour than offenders made using conventional questioning and monitoring.

I have no strong views on the ability of polygraph tests to prove guilt, or innocence. Though I am impressed by people, like my two correspondents in prison, who volunteer for testing. In both cases, I would be convinced of their innocence, tests or no tests; the evidence I have seen in their favour leaves no room for doubt. One of them, Jeremy Bamber is, in my view, a victim of one of the gravest injustices of our time. The report of his lie detector test states unequivocally that there was "no deception indicated" in his replies – to questions on the murders of five members of his family.

It must be galling for Bamber to see the system, which does not recognise this test and continues to incarcerate him, now proposing to lock people up on the strength of precisely the same test methods.

A whiff of hypocrisy? Full-on stench more like.