I am probably one of the few who think use of a stun gun on JB does NOT rule out a family member. The videotape indicates that they had one, IMO, regardless of whether it was found in the home. The stun gun could have easily been snuck out of the house.
I do doubt it had been used on other occasions. The marks are just too telling and actually look so much like cigarette burns that SOMEONE would have seen them at some point. This child wore skimpy costumes, took dance classes, etc.
I do agree that it is very suspicious that requests for an exhumation (when it was still early enough to render the information) were denied. I mean, if LE wanted to test YOUR murdered child for evidence they'd been stun gunned, wouldn't you say yes? Not if you KNEW for sure and knew who had used it.
Of course, the DA could have gone over the parents' refusal and gotten a judge's warrant, but he refused to do so. Boy, NOBODY was in that little girl's corner in that DA's office, were they?