It would be nice if we could use Karl Popper's standard -falsification- to examine various theories of the case. Alas, that is not possible.
Much of the evidence is equivocal. Very little is not in dispute.
We have a dead body, we know the COD, and approximate TOD. We know the body was found in the WC at 13:05.
We know there is a garrote on her neck, and that she had been bashed in the head.
We know the items that were found in the WC (to the extent nothing has been withheld from the public)
We know there was a handwritten RN, on paper sourced from the victim's home. We know the exact wording of the RN, but not necessarily the exact meaning of everything in it.
We know that PR called the police at 05:52.
We know police failed to secure the crime scene, and that multiple searches of the house were conducted by police and freinds. JB remained undetected for about 7 hours after the 911 call.
We know JR told the police that he'd checked all doors and windows and all were locked. We know he told them that he himself broke the basement window. We know the police report would say there were no signs of forced entry.
We know JB ate pineapple and that she must have done so about 2 hours before death.
I'm not making a detailed and exhaustive list. There are a few other things we know. The point is, only one or two handfuls of facts are not open to interpretation.
All theories of the case that do not contradict these few undisputed facts are possible theories. Even the infamous IDI theory. The most that can be done is to suggest that IDI is extremely unlikely - and one can do it in a snarky manner, which is funny, but it can't be falsified. Try if you will.
All theories require assumptions. They require us to use our common sense and our own life experiences to say what seems likely/unlikely.
All theories are opinions. Most of us here have rejected IDI, but it's not because IDI has been falsified, it's because it strikes us as extremely improbable.
As an example of taking this falsification approach, and of how little value it is, we might look at the Rs version of events wrt the pineapple.
It has been said that the Rs version falls down because of the evidence that JB ate pineapple. But it doesn't. The Rs version of events is that they put JB to bed and they don't know anything about her eating pineapple after the party. Do we reject the idea she was put to bed shortly after arriving home? If we do, we make an assumption. The Rs don't claim that she didn't eat pineapple, just that they don't know anything about it. Their version of events is consistent with an IDI theory where, for some reason, the intruder entices her out of bed with pineapple.
We might regard such a theory as unlikely, (I certainly do) but we can't falsify it.
We can go on and on, showing how very little can actually be falsified, but there is no need. Most of us understand that solving the case mainly boils down to is what is likely. More correctly, what strikes us as likely, or fantastically improbable. Since people are different, this accounts for the wildly different theories of the case.
The courtroom standard is reasonable doubt. If the standard were that the prosecution's case had to be unfalsifiable, there would almost never be convictions.