Apologies in advance for the long post. I'm just putting some of my thoughts out there! I'm not sure if anybody has seen the autopsy photos of Marcia online. There are 2 readily available photos showing her face (I don't want to post them here in-case it breaches the rules). There appear to be 3 distinct injuries to her head. There is a wound above her left eye just on her hairline, another in the centre (again, on her hairline), and then a larger wound slightly lower down and above her right eye. I suspect the larger wound is actually a collection of up to 4 separate injuries. There are a few things that struck me about these images:
1 - I find it odd how central the injuries are. Had she been attacked from a few feet away with a longer implement and the offender was trying to beat her with it, it is likely that the injuries would have been more to the side of her head as she turned away. Similarly, if the offender was up close and attacking her whilst she was on the ground, for example, her natural instinct would have been to turn her head away from the incoming blow. She can't have done this. There are no obvious injuries to the side of her head or face. I think it's possible that the offender beat her as he was strangling her, or whilst she was unconscious.
2 - In addition to the cuts, there are significant marks on her forehead. Some of this will likely be hypostasis (blood pooling) that occurred post mortem given that she was found on her right hand side in the foetal position, so the blood would have settled primarily on her right side. However, I think some of it is bruising - there are clearly marks and discolouration on the left side of her head. Is it possible that she was beaten with a fist? This would likely cause the bruising but would not necessarily cause open wounds.
3 - The cuts that were caused seem to be very small and quite uniform. I'm struggling to think of such a small, handheld implement that would cause such injuries. I wonder if a fist, containing a ring, would cause those injuries? These don't seem to be the large/uneven type of injuries one would see with an implement such as a rock or a bat etc.
4 - Apparently she also suffered a lacerated liver. This can be caused with high impact blunt force trauma injuries, often where the liver impacts the chest wall, and can be seen with high speed car accidents. The force used to lacerate her liver must have been significant, and could easily have been caused with a fist.
5 - Unless there are significant injuries that are not in the public domain, from looking at hear head and also the lacerated liver, it seems the majority of the injuries are on her right side. Almost as if the offender has pinned her down and is beating her from above as he's immobilising her by strangling her - she's struggling, so he beats her to prevent this. If he's beating her primarily on her left side then it stands to reason that the offender would be left-handed (otherwise the impacts would likely be more on her right side).
Again, I'm just wanting to bump this thread and get my thoughts out there. It would be really interesting to hear what anybody else thinks about the above, however!