Sex offenders may soon be asked to take lie detector tests to monitor their behaviour, the national probation service said today.
The machines, which monitor physical responses such as heart rate, could be used regularly if further research proved their reliability, the service said.
Polygraph tests were tested by the national probation service in a series of low-key trials last year, and the use of the machines is still at a very early stage.
National probation chief Eithne Wallis said more research was still needed following the tests, by two American polygraph examiners, in the West Midlands, Northumberland and Surrey.
“If it worked and if there was a robust, demonstrable level of reliability it may be that there would be a place for that as a piece of supporting information in our management of sex offenders,” Ms Wallis told the BBC Radio 4 Today programme.
A total of 30 sex offenders on probation were asked a series of questions about their past offending, current behaviour and fantasies.
They were asked if they had been in contact with children or on the lookout for victims.
The BBC reported that the tests prevented at least three offenders from committing further crimes.
Sex offenders have been subjected to lie detectors in the US state of Arizona for the last 12 years.
Sandy Gray, a polygraph examiner for the US state, told BBC Breakfast: “They [paedophiles] are very deviant and usually very skilled at being manipulative.
“By monitoring, the polygraph examination is, by far, better than simply accepting and taking their word for what they are doing.”
Ms Gray said the machines monitored blood pressure, heart rate, sweating and breathing patterns.
As well as sex offenders, detectors in the US have also been used in criminal investigations, custody evaluations and professional sexual misconduct cases, while US police departments have even been known to use them in pre-employment checks.
Doubts over the accuracy of polygraphs mean they cannot currently be used by police in the UK and are not accepted as evidence in the courts.
Polygraph examiner Bruce Burgess is one of only two working in the UK and his clients include employers who suspect staff of theft or fraud, and people checking if their partners are being faithful.
Forensic psychiatrist Professor Don Grubin, who oversaw the tests, said the convicted paedophiles had disclosed unauthorised contact with children and that they had visited areas where they might meet children.
But Roger Stoodley, who led the investigation into the paedophile network that included the notorious child killer Sidney Cooke, said he was sceptical of the development.
Sex offenders are practised liars and would be able to fool the most sophisticated equipment, he said.