The £4,000 machines monitor the breathing, blood pressure and heart rate as subjects answer questions.

Among those returned to prison were people who had originally been convicted of rape, sexual activity with a child, sexual grooming of underage girls and possession of indecent photographs of children. […]

David Spencer, research director at the Centre for Crime Prevention, said: “Reoffending rates in the UK are still at scandalously high levels and any means by which potential reoffenders can be identified has to be welcomed.

“Now that it has been proved that polygraph machines have kept 23 potential sex offenders off the streets, it is high time that the technology was rolled out more widely.”