SUSPECTED sex offenders have been targeted with lie detector tests in a trial by Hertfordshire Constabulary.

The Polygraph tests monitor heart rate, brain activity, sweating and blood pressure during questioning, and were used by experts working with officers from the force’s specialist Paedophile Unit.

Suspects were probed ahead of charges being brought.

All 25 ‘low-level’ first time suspected sex offenders volunteered to co-operate with police - however evidence elicited during the examinations is not admissible in court.

Detective Chief Inspector Glen Channer from Hertfordshire Constabulary said: “The Polygraph Testing provides us with an additional tool and has cut down investigative time significantly leading to a more efficient process, often helping to identify additional offences.

“The integrity of the process is paramount and we are working with a highly credible expert in the field on this trial, Professor Grubin from Newcastle University.”

The Association of Chief Police Officers are monitoring the study and have been offering advice to the force.

However the body said the tests are in the early stages and “are by no means a single solution to solving crimes”.

“We monitor any new approaches or technology which could provide a positive benefit in helping investigate crime, support victims and put offenders before the courts,” said an ACPO spokesman.

“The ACPO Homicide Working Group provides advice to the police service on the use of polygraph techniques and will follow with interest the latest study led by Hertfordshire Constabulary.”

A further 12-month trial is expected to start in April.