Friday 10 August 2012 07.30 BST
Why giving polygraph tests to sex offenders is a terrible idea
"Polygraphs are notoriously unreliable and easy to fool, and sooner or later sex offenders will discover the truth about them
In the pilot study it was sex offenders' belief in the polygraph that made them reveal the truth, not the test itself.
It was recently announced that the government is keen to introduce mandatory polygraph testing for rapists and other serious sex offenders when they are released from prison, in the hope that this will reduce re-offending rates and thus protect the public.
It seems, however, that these encouraging results were based not upon the ability of the test to detect when offenders are lying, but instead upon the offenders' belief that the test was capable of doing so. This raises serious issues regarding the wisdom of rolling out such a scheme on a mandatory basis across England and Wales."