good points.the only other option I see is Patsy killing her..for whatever reason,accidentally or no...but then...she gets JR(rem. her saying the murderer confided in someone?)..who decides they must get her out of the house...so he stages the sexual wound (to cover past abuse,as well as it will throw in a sexual reasoning to it),ligature strangles her,and together they write the RN.
Then they decide to leave her in the WC instead,thus the rest of the coverup begins..the large underwear,etc...JR may have asked for more WED. underwear,insisting on it,only to be told by PR the large ones are all she has...so better than nothing,he uses them.Or patsy may not have been present in the final staging,although she knows it's going on.But I'm not sure JR would have known that underwear was even there without Patsy telling him.
Would that work,too? Help me out here if not,as I may have missed something.
The only reason that doesn't work is that the vaginal injury was inflicted before JBR died. So at this point, if PR has inflicted the head wound and JR the ligature strangulation, technically it is JR who is the murderer!
Also, I can't see any reason at all for the WED underwear as opposed to any other pair, unless the parent responsible for JBR's death knows that the other parent knows which pair of underwear she was wearing to bed. Why else would you chose that particular pair of underwear?