This expands to protect the public from any pursuits, because their conduct shows that they have low impulse control, and respond vigorously to stimuli that they see as appealing. I'm sure you're glad that there is a way, despite all of the financial, psychological, and bureaucratic hangups, to keep the predators away from your family and friends. If your facility does, then I think the community needs to be protected from your facility as well. Plethysmograph data is totally useless for determining guilt or innocence regarding deviant sexual acts. It would be like using a personality test to convict someone of burglary.
Plethysmographic data have no diagnostic value of any kind.
About one-third of offenders show no arousal in the lab. The proper stimuli to use are not pictures, but taped fantasies. Ideally taped fantasies spoken by the offender themselves, describing the offenders' own fantasies as well as contrived ones. The value in plethysmographic assessment is to aid the offender in learning how to control erection responses during deviant fantasy. Treatment should not be court-ordered.