Paedophiles and other sex offenders on probation will face compulsory "lie detector" tests from next month, The Register has learned.

The academic who will run the tests of controversial polygraph technology on sex offenders for the government believes a successful trial will lead to its use in other crimes.

From late April, sex offenders released on licence in the West and East Midlands* National Offender Management Service (NOMS) areas will be required to undergo a polygraph examination within three months of release, and then at six week intervals until their probation is served. The first licences including compulsory testing have already been granted.

Then-Home Secretary David Blunkett first indicated government support for compulsory testing of sex offenders in 2004, but unspecific plans for a trial scheme this year weren't announced until last September.

Offenders who refuse to submit to the programme will violate their licence conditions and be sent back to prison. It's expected that by the end of the trial between 600 and 1,000 primarily child sex offenders will be subject to regular examinations.

Newcastle University's Professor Don Grubin, who will run the three-year experiment for the Ministry of Justice, said at the end of the trial the government will have to decide whether to use polygraph testing nationally, and whether to extend it to other crimes.

"We need to not outrun the evidence, but provided there is good evidence of success, I would say the argument then needs to be turned to 'what's the justification for not using it [for other offences]?'," he said, citing US authorities who have use polygraph testing in drug addiction and domestic violence probation.

Grubin previously ran smaller, voluntary trials of sex offender polygraph testing for the government between 2003 and 2005. During examinations, volunteers were asked about their contact with children, for example. Researchers found that offenders were more likely to make disclosures about their behaviour if challenged with polygraph results indicating they had lied or withheld information.

According to the Polygraph Rules 2009, the statutory instrument recently approved to govern the new trial, "a polygraph examination must include... at least one, but not more than four, relevant questions."

The laws to allow compulsory polygraph testing by probation services, brought in during 2007, do not limit the technology to sex crimes. A Ministry of Justice spokeswoman said the government was not currently considering polygraph testing for non-sexual offences and couldn't say whether it will be considered in future. "We'd have to analyse the outcome of the trial before we'd look at that," she said.

The main equipment supplier for the trial will be Indiana-based manufacturer LaFayette. Its polygraphs measure heart rate, sweating and breathing (abdominal and chest).

Polygraph testing of sex offenders is in widespread use in the US, but according to Grubin, "it varies in terms of how mandatory it is". "The problem is there has been a lack of good data on its effectiveness," he said.

Grubin added that given the vulnerability of polygraphs to faking, no decisions about the management of recently-released sex offenders would be made solely on the basis of their results. ®

*The specific prisons and probation offices covered by NOMS East and West Midlands are listed here and here.