Don Mackay reports for the Mirror:
PAEDOPHILES and other sex offenders could fool lie detector tests, experts warned yesterday.
As part of bail conditions the Home Office is drawing up plans to use polygraphs to monitor whether sex offenders will strike again.
But the British Psychological Society said the tests could be beaten – and are anyway far from accurate. One study of polygraph techniques used in criminal probes found up to 17 per cent of guilty suspects “cheated” and were found innocent, while as many as 47 per cent of innocent suspects were classed as guilty.
Tests are based on physical responses – such as increased sweating, heart-rate, blood pressure and respiration – to questions.
But the BPS found subjects could suppress their reactions.
Professor Ray Bull of Leicester University, who chaired the working party, said: “We must not deceive ourselves into thinking there will ever be an error-free way of detecting deception.””
A Home Office spokesman said polygraph tests on sex offenders and others were still at the pilot stage.
He added: “We have found tests encourage offenders to disclose previous offences and current behaviour.”