Forensic specialists say that up to an hour could have elapsed between the head blow and death. "This isn't something that kills her quickly" was the quote. Adrenaline kicks in and who knows what someone is capable of?
The reason why I don't feel the head bash was staging is that it was not apparent until the autopsy. The coroner was surprised to find it, in fact, and did not find it until her scalp was pulled back for preparation of the removal of the skullcap to examine and weigh the brain (standard procedures). Because it was not VISIBLE as a cause of death (but of course, WAS one of the two CODs), it was unnecessary as staging. It added nothing.
BUT on the other hand, if the head bash came first, you have the problem of a (seemingly) dead little girl with NO apparent reason for her death. So the garrote was made as staging so that there was an immediately obvious cause of death. Of course, she was still alive when that happened. Some people speculate that IF there was an erotic strangulation it may have been done with something softer, like a scarf (JR oddly chose a scarf that he had been given as a Christmas gift to put around JB in her coffin). I have to point out that there were NO other marks on her neck except for the marks made by the garrote and petechiae. BUT if you look at photos of victims of strangulation with a scarf or other soft ligature, there are IDENTICAL red triangular marks on their throats to the one JB had. There were such photos on Ruthee's Pages (on ACR) but Ruthee's site is pretty much unavailable as she has been dead several years now. Those photos were posted here a while back.
The deep ligature furrow on JB was red, which was one of the things (along with the petechiae) that indicated she was alive when she was strangled. There also seems to be a ligature mark (not a deep one) that was WHITE, indicating it was made AFTER death. There is no way to tell how much time elapsed between the red and white marks, but the white mark was made while she was in the early blanching stage of livor mortis, before it became fixed. The cord was long enough to have wrapped a few times around, even after the tightly knotted section that made the deep furrow.