What offense could someone goto jail for that would be unpardonable?

So simply: CAS has issued me a warning stating that if I let my mothers husband around my child alone, around bathing or changing or when she is naked... you get the point right? They also asked me to inform them if he was interacting with any children or lived in an area with children which I am starting to think maybe I should have mentioned the neighbours kids, but I'm not out to destroy lives here.

What I would like to know is - John Howard society paid to have his finger prints run to have a criminal record check done so that he could pursue a pardon. When things came through, he was told that he didn't have a pardonable offense and that they wouldn't even take his application for pardon. So what could he have done. I have a story that he got into some bad stuff, but I would assume assault and drug related charges would give probability of a pardon?

I've been trying to find things, but my family is not being honest with me, so I can't say what his offense is and whether I should take the CAS seriously, or if they can even do anything anyway. I don't even know what to do because to cut him out of life, means my mother as well as she refuses to come visit me and will only have me visit her. I'm stuck, I just need to know if the reason the CAS is telling me these things is linked with an unpardonable offense, and what those offenses would be.