Autopsy report lists the cause of death as "asphyxia by strangulation associated with craniocerebral trauma." Since this conclusion references two injuries that would have proven fatal but does not place them in chronological order, this has been an area open to debate.
IMO, the wording suggests that the strangulation was the actual cause of death, and that is supported by the noted petechial hemorrhaging of the eyes and eye lids (classic indicator of death via strangulation). This is also supported by the internal bleeding of her brain into her skull (heart still pumping), and the amount of that bleeding has led experts to estimate that JBR died roughly 45 -120 minutes after the head blow (expert opinions on this timeframe vary greatly).
This alone does not provide a sequence of events. For example, JBR could have been in the process of being strangled when the head blow was inflicted. However, there are no scratch marks around the neck ligature indicating that she struggled. There are small marks that many have speculated to be fingernail scratches, but the autopsy report lists them as additional petechial hemorrhages, and they do not match with the longer scratch marks that one expects to see in such an event.
One could argue that JBR was restrained by the wrists or some other fashion and therefore was not able to struggle against the ligature as would be expected. However, the wrist bindings were noted to be loose enough for the ME to put his finger between the cord and JBR with no problem, and the ME was able to slip them off her wrists without untying them. The ligatures were also found over top of JBR's sleeves, and there were no ligature marks on her wrists. This means that she could not have been completely restrained by the wrist ligatures, and it reasonably follows that she was unconscious at the time of strangulation.
Still, even if she was unconscious when strangled, does that mean she had already suffered the blow to the head? In the opinion of many credible experts, yes. Per the autopsy report, JBR's blood ethanol and drug screens were negative, so she was not sedated. A stun gun jolt does not knock a person out, and it has been summarily proven that the abrasions on JBR's body were not caused by a stun gun. So barring the introduction of new evidence, there is at this point no forensic explanation for her to not struggle against the strangulation unless the head blow occurred first.
In the A&E documentary and others, Lou Smit claims that the head blow couldn't have come first because "the blow to the head would have been so massive, it's unlikely that she would have been able to struggle" and "that lack of bleeding from the head wound indicates she was near death from strangulation before she was hit." The head blow was massive, and it would have knocked her out cold, but it wasn't massive enough that it perforated her scalp. Smit's observation about head wound bleeding is speculative and does not match the autopsy findings - perhaps he is referring to external bleeding and ignoring the rest. We also have to keep in mind that use of a stun gun is critical to Smit's theory that the head blow was the death blow, and the stun gun argument has been scientifically disproved (the distance between the marks does not align with a stun gun, stun gun injuries create burns and not abrasions, stun gun marks on a conscious victim are not small and perfectly shaped due to the victim's body moving when the jolt is delivered, stun guns cause extreme physical pain and deliver electric energy to the body as opposed to causing the victim to become unconscious, and the manufacturer of the stun gun reported to be used has gone on record stating that there is no way the marks on JBR's body were caused by a stun gun).
None of this points one way or another as far as Intruder versus Ramseys, but it does do two important things:
(1) Makes it nearly impossible to scientifically support the idea that the head blow came last.
(2) Indicates that the wrist ligatures were staged as they served no functional purpose.