Neil you could say God Help us as they are used by the Probation Services for sex offenders 
I know, I did find this rather suprising. I also heard that they were used by a Police force, although I forget which one. I know that I would never take one if I were innocent, I would be terrified that the test would come out wrong. Anyway I'm off to Wimbledon now, once I've done a quick sun dance. Have a good day.