EXCLUSIVE: Police use lie detector tests to help manage sex offenders

Greater Manchester Police are tackling the growing number of sex offenders in our communities with the use of lie detector tests. There are around 3500 registered sex offenders in the area, officers say the number is growing by 10% per year.

The force told us their specialist officers are responsible for keeping tabs on 65 sex offenders each - which is way over the recommended national guidelines of 50.

GMP were one of the first forces to introduce polygraphs to help keep tabs on offenders, Granada Reports has been granted special access to see one take place.

DCI Jude Holmes told Granada Reports it's just one tool they use:

Sex offenders can be made to take polygraphs but the man here today has come in voluntarily. He now lives in the community after spending time in prison, and tells police he will not offend again, but it's up to officers to determine the truth.

A specialist unit spends hours visiting registered sex offenders in the community, checking devices and monitoring activity. They hope the polygraph can be used to focus attention on those most at risk.

The offender with us when we visit the unit was jailed for sex crimes against children. He is interviewed before the polygraph takes place, this is final opportunity to make any confessions and divulge information that could come up later.

He is then hooked up to various sensors and and the test begins. Questions including sexual contact with children are asked. The offender responds 'no' to all of them. The questions are asked again to see how the responses match up. The test itself is over in a matter of minutes.

Assessment by the polygraph examiner reveals he's telling the truth. This could mean a lowered risk level and in future less contact with police.

The ex-convict here today told Granada Reports thought the tests were "necessary" to "prove you're not doing anything to harm anybody."

Polygraphs can not be used in court and aren't 100% accurate but GMP say 80% of the ones they've conducted so far have led to further intelligence and even arrests.