The 'sexual assault' thing is the reason I think JR is the one responsible for JBR's death, and that PR is his accomplice after the fact, which I know is the exact opposite of how everyone else looks at this.
I think that wound was inflicted, not to stage a pedophile intruder scene, but to cover up prior abuse. As I've said before, it was inflicted on a still-living child within, at most, an hour of the head blow, and before the strangulation. So who could have inflicted it, if not her killer? And why would her killer inflict it, if not to compromise evidence of prior abuse?
So, if PR is the killer, then PR inflicts the head blow, inflicts the vaginal wound, completes the murder by strangulation, cleans up evidence of the vaginal wound to hide it from JR, and then gets JR involved in the cover up.
Or, if JR is the killer, then JR inflicts the head blow, inflicts the vaginal wound, completes the murder by strangulation, cleans up evidence of the vaginal wound to hide it from PR, and then gets PR involved in the cover up.
The only reason to clean up the vaginal wound is NOT a change in staging; neither JR nor PR is stupid enough to believe that the wound won't be discovered during the autopsy. The only reason to clean up the vaginal wound is to hide that, and that alone, from the person who is going to help you cover up this crime.
Everyone thinks JR would automatically cover up for PR, so as not to lose her, his lifestyle, his status in the community, etc. But any or all of those reasons could be reasons for PR to cover up for JR as well, especially if JR managed to make her believe that BR might have committed the crime.
I know it could be either way, here. PR might have been molesting her daughter, and might have needed to cover the evidence, necessitating the vaginal wound. But to me, the key piece of evidence is the size-12 underwear, for two reasons: one, PR would have known right away how ridiculously large those were, so it's hard to imagine her using them (why put underwear on JBR at all, in fact? The long johns would suffice), and two, unless I'm wrong, the fibers from JR's shirt were found in the crotch of the size-12 panties, which is a pretty strong indication that either he handled them, or else PR deliberately placed the fibers there to implicate him.
I think we can reject that second option, btw. If PR knew that much about fiber evidence she'd have taken more care of her own fibers, particularly her sweater fibers which I believe were transferred as she helped in the staging. (The tape, for instance, and I think at some point she hugged JBR when the rope was just a rope, before it became a garrote, which was how her fibers ended up being twisted into the knot.)
But if we reject that second option, that means that JR did handle the size-12 underwear, and did help clean up the vaginal wound--which, by my way of looking at things, means that he was the one who inflicted it, since the clean-up ONLY makes sense if it's seen as an act designed to hide that wound from the accessory after the fact.
But if he was the one who inflicted it, between the head blow and the strangulation, then there's pretty good reason to believe that he is the killer...