In the same week that critics denigrated the proposed use of the polygraph to monitor terrorists, a police lie detector test for sex offenders demonstrated perfectly how they work.

Dark Justice

Paedophile, David Nicholson arranged to meet a 13 year old girl that he had been chatting to online. What he hadn’t appreciated was that the ‘child’ was actually a snare set up by vigilante paedophile hunters, Dark Justice.  Click here to watch them apprehending him.

As can be seen in the video Nicholson is caught off guard. He admits arranging to meet a child but then denies chatting to children online.  The police arrive and he is arrested.


Subsequent to the arrest in 2018 the police asked if he would voluntarily take a lie detector test, to which he agreed.  In the course of the test, Nicholson confessed to previously raping an 11 year old girl.  The results from the test were then used to further investigate the matter and the police were able to find the victim.

This week Nicholson was sentenced to 9 years and 4 months incarceration plus 2 years on extended licence. His crime may never have been identified if the results of the lie detector test for sex offenders had not been used.  He may never have been convicted had it not been for the immense courage of his victim in assisting the police. As a survivor she provided police with all the evidence they needed to prosecute her attacker.

Lie detector tests for sex offenders

Many UK Police forces have been using polygraph technology for well over a decade.  But there is a general misunderstanding fuelled by misinformation as to how it is used.

Nicholson was not convicted with polygraph results but those results were vital to the further investigation police needed to do.

11 police forces throughout the UK have tested 4,000 sex offenders out on probation since 2014. More than 350 have failed the tests and have either been returned to jail or changes have been made in their licence conditions.  This was debated on BBC Question Time this week and you can watch it by clicking here.  Mike Barton, former chief constable of Durham Police, said that lie detector tests “put pressure on people that they need to tell the truth”.

Myths and criticism

We have listened to critics saying that the polygraph is pseudo-science, not 100 percent accurate and that it can be beaten.  These are tired arguments when you research its successful use as an investigative tool in law enforcement.

There are few things that can be described as 100 percent accurate.  Indeed eye witness testimony is infinitely less accurate than the polygraph.  Research conducted by the Innocence Project , looked at 358 convicted prisoners from 1989 awaiting the death penalty in the USA. Exonerated by DNA evidence, these people lost an average of 14 years of their lives behind bars. Over 70 percent of them had been convicted through eye witness misidentification. The polygraph is between 95 -98% accurate, depending on the qualifications and experience of the examiner. When DNA evidence is not applicable would you prefer to rely on eye witness testimony or the polygraph to prove your innocence?

We fully support the Government proposals for using lie detector tests to manage and monitor terrorists.  If it saves lives how could we not?