Thank you for this clarification. If your son had been accused of a new crime, then I would have suggested that he invoke his 5th Amendment rights against self-incrimination.

If this is your son's first polygraph interrogation, then I suspect he is in for quite a grilling about his sexual history and any other past offenses for which he may not have been convicted. He still has the right to invoke his 5th Amendment rights if the answer to any questions asked would incriminate him.

What right, if any, does your son have to have a lawyer or parent present when he is interrogated? Have you consulted a lawyer regarding your son's options?

You will want to learn how polygraph "testing" actually works. It has no scientific basis, but is instead fundamentally dependent on trickery and has an inherent bias against the truthful. You'll find this explained in detail in Chapter 3 of AntiPolygraph.org's free book, The Lie Behind the Lie Detector, which you can download as a PDF file or browse on-line. You can then speak with your son about some of the nonsense he can expect to encounter during his polygraph interrogation.

In addition, after you've learned how polygraphy "works" (and doesn't), you'll find some documents related specifically to post-conviction sex offender "testing" on the AntiPolygraph.org Reading Room page. (Scroll down to the "State and Local Polygraph Documents" section.)

Also, see the Post-Conviction Polygraph Programs forum on this message board for commentary by others in your (and your son's) situation.