It seems tampering with evidence and <RSBM for focus> would create plenty of reasonable doubt.
RSBM
Are you referring here to possibly alleged planting of taillight pieces in the snow?
Because I think it's been proven, IMO, that there wasn't opportunity for that on 29th Jan 2022.
SERT was on scene while the Lexus was enroute to the sallyport, and dug out the first pieces of taillight (about 5 or 6 pieces IIRC in total just from the road area) from fresh undisturbed snow at the side of the road at 5.45pm. The Lexus arrived at the sallyport on the transporter at 5.35pm, before it was then unloaded and driven into the sallyport. Proctor was still at the sallyport when those first taillight pieces were found. 22 inches of snow had fallen by 6pm. They started with the road so that any evidence in the snow wouldn't then be disturbed by a plow.
SERT continued to dig and found John's shoe up against the kerb, under the snow, before they left for the night at about 6.30pm. His broken bar glass had already been found under the snow about an hour after his body had been removed from the grass area, near to where his body had lain.
IMO there wasn't opportunity, or perhaps more importantly, a motive to plant evidence.
As regards motive for planting evidence, Karen hadn't told anyone John went in the house, and had told police she didn't see John go inside the house, which is why there was no probable cause for getting a search warrant for the house, together with statements from other witnesses at the scene that morning and at the house the night of the incident, and she had already told two paramedics separately that she hit him, so they had no reason that day to think she would change her story.
Additionally, what difference would it make to the police if they found less or more of the taillight at the scene? Just one piece matching Karen's Lexus is enough to show she broke it there. If Proctor took more taillight pieces from the sallport to plant over coming days, why would it make any difference to him how much was found in total, after those first pieces had been found, or whether it was all found on one day or over several days? Why not do it all on one day so that there would be less chance of him being spotted by anyone tampering with the scene? How did he get a hair with John's mitochondrial DNA and get it to stick on the car while it still had snow on it, and stay there after melt so that the technician would find it? How did he get John's DNA onto the taillight housing? Why would Proctor have a theory for how John was injured, if he knew crime scene technicians would be processing the evidence and it might not match up with his theory? The ME hadn't even conducted the autopsy yet. It was years before the techstream evidence and John's complete phone evidence (including battery temperature) would be fully analysed, showing the timeline of events. There has to be a method and a reason for theories advanced, yet I've seen no critical thinking applied to it. It doesn't withstand scrutiny, IMO.
All IMO