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. …