I have a sex offender that was placed on REGULAR probation in 2000 via plea agreement. This person is a walking time-bomb and needs to be sent to the pen. However, I believe the plea was invalid and must be set aside. What is the best approach for dealing with this?

I believe the judgment is void ab initio and you need to redo the plea

This is about the third time this issue has been raised in this user group. If a defendant didn't object at the time he was given probation, then it is not void or voidable. He waived his right to object and you can proceed to revoke.

Check out Ex parte Williams, 65 SW3d 656 and 47 SW3d 177.

If you catch the mistake before leaving court, however, you should correct it.