Even if it had been inadvertently placed there by either June or Nevill during a fracas in the kitchen between the three of them I'm sure there'd have been blood elsewhere while this task was carried out. It's not impossible that either parent could have put it out of harms way of Sheila doing more damage.
We just don't know. Nobody does.
I think it's the other way round. First, if Sheila had already started shooting and/or wounded somebody and Nevill had managed to seize the rifle from her, the police would have been called and the incident would have ended there and then, so the issue of blood traces would have been moot. If Sheila was the killer, then she must have caught Nevill off-guard somehow or escaped from him.
Second, Nevill (and/or June) would not have just moved the silencer. They would have moved the rifle. Furthermore, if we imagine a scenario in which, after Jeremy leaves, Nevill has returned the rifle to the gun cupboard, then a factor to consider is that the gun cupboard was supposed to be locked and secured per the conditions of Nevill's firearms certificate but wasn't. It wasn't even lockable, despite Nevill's arangements having been inspected by an Essex police officer a few months before. This can clearly be seen in the photographs. This means there was no way for Nevill (or Jeremy himself) to secure the firearms against Sheila or a third party intruder.
I believe it follows from all this that:
(i). in an alternate scenario in which Sheila is the killer, there cannot have been any immediate prior incident in which Sheila used or threatened to use the rifle, which means that Sheila did not enter the den that night, and Sheila must have gone downstairs and into the back corridor alone. Sheila would not then detach the silencer prior to shooting the family. She would simply pick up and use the rifle with it left on. This, I believe, explains Rivlin's defence strategy; and,
(ii). logically, only two people could have detached the silencer and replaced it in the gun cupboard prior to the incident: Jeremy or Sheila. If the killer was Sheila, that means either there was a long pause before her suicide, or an innocent Jeremy had detached the silencer at some prior point. Conversely, if the killer was Jeremy, then he has somehow managed to leave the silencer in the cupboard without leaving any transferred blood traces anywhere.
With the luxury of hindsight we can see that a different conclusion is possible to that of Rivlin, which is that the silencer was taken off the rifle by Jeremy before he even returned to the farmhouse and witnessed the family meeting in the kitchen. He did not take the silencer off the rifle only at that point, but some time before then, maybe days before, maybe earlier that day, who knows? He probably can't remember himself. The significance of the point is that it allows the possibility of the silencer being found by somebody after the shootings and maliciously or mistakenly entering it into evidence against Jeremy.
To my mind, Jeremy's story of him shooting [at] rabbits just prior to leaving for home supports his claim that the rifle did not already have the silencer on it, implying that the silencer has been removed at some undetermined point prior to that. He would not have gone out and started shooting [at] rabbits with the silencer on, as this would not have scared off the rabbits. I do think he was shooting at the rabbits more than shooting the rabbits - if you see the distinction. You don't use a rifle like that just to shoot one rabbit after another. It's not possible. Anybody familiar with these firearms will, I hope, concur with me on that point.
