Lie detectors are used to confront sex offenders

Britain set to follow US example and use polygraph tests for criminals in spite of international concern over their results

IT WAS while working as a police officer on the streets of Chicago that Dan Sosnowski first became convinced of the value of polygraphy in penetrating the criminal mind.

IT WAS while working as a police officer on the streets of Chicago that Dan Sosnowski first became convinced of the value of polygraphy in penetrating the criminal mind.

Two decades later he is at the forefront of official trials which could see the results oflie-detector equipment produced as admissible evidence in British courts of law.

Last week in Birmingham, Mr Sosnowski, now an independent polygraphic consultant, subjected child abusers and rapists to a two-hour grilling intended to discover whether they were honestly co-operating with therapists.

Each was required to sit in a chair with tubing wrapped around their stomachs and waists to monitor respiratory changes as they answeredquestions. A blood pressure "cuff" was tied to upper arms to measure variations in heart rate, while skin response equipment was fitted to fingers to record perspiration levels.

Using the "control question" technique, Mr Sosnowski asked a carefully prepared mixture of "neutral" ,"relevant" and "control" questions. Neutral questions related to innocuous personal information, control questions tackled general areas of honesty and criminality, such as: "Have you ever lied on a job application form?" Relevant questions were focused on abuse such as: "In the past six months have you touched a child for sexual gratification?"

The rationale is that with an innocent person the control and relevant questions will elicit a common physiological response, while those who are guilty will respond more vigorously to the relevant questions. As the paedophiles answer, their body reactions leave a graphic response across Mr Sosnowski's computer screen.

For Dan Wilcox, a psychologist working with paedophiles for the West Midlands Probation Service, the results could be invaluable. "We never know for sure whether we are being groomed by the sex offenders who are saying the things which they know will have the desired effect. We have to be aware that we may be being given safe soundbites."

Mr Sosnowski, who is a senior figure in the American Polygraphic Association, said frequent use of the tests also provided a "monitoring tool" for overstretched probation teams and an "artificial conscience" for the offender. He said: "Unfortunately, with individuals on probation, you cannot watch them for 24 hours. However, they are constantly aware that they are going to have to take their regular polygraph test and that they will not be able to get away with their behaviour."

According to Mr Sosnowski, the testing also helps to break the offenders links with paedophile rings, who no longer wish to associate with someone who may "spill the beans".

David Middleton, a senior probation officer and head of the West Midlands sex offender treatment programme, said that the results could help staff target resources on the most dangerous offenders.

He agreed that some people would be concerned that devious offenders would find a way to exploit the new technique. "But the evidence that we have heard is that it is harder to trick the machine than it is to trick the therapists," he said.

The West Midlands service has already set up a therapy-based sex offender treatment programme, which is to be adopted across England and Wales, after tests showed that it drastically reduced reoffending rates. Levels of reconviction for child sex abusers on the programme were 3 per cent for sexual offences and 8 per cent for all offences, compared with 10 per cent and 32 per cent for similar offenders not on the programme.

Mr Middleton said he hoped that polygraphy could be built into the programme with the same success as in America, where it is used by most government agencies.