I agree that it is highly unlikely that Sheila fired 25 shots + reloaded the rifle without getting gun residue on her. On the other hand, I find it hard to trust the police-and forensic findings. This case was handled so sloppily, that it is very, very hard to form an opinion.
I don´t know a whole lot about this case - just learned about it and started looking into it about a week ago. So please bear with me!
Points so far that have set an alarm in my mind:
-It is stated clearly in police notes that one male and one female body was discovered downstairs - three additional bodies were discovered upstairs. Then later, one male body downstairs and four bodies upstairs. How does THAT happen? You don´t "see" a body that isn´t there!
-Looking at police photos of Sheila´s body, it is clear that the police moved her hand and the rifle around. Why?
-Police didn´t perform a thorough search of the farmhouse. They overlooked the silencer found by relatives a month or so after the killings. Or wasn´t it there in the first place? After it was in the police´s possession, it was handled very carelessly, yet it was used as a crucial piece of evidence against JB.
-What about Sheila´s heavily bloodied knickers found in a bucket in the kitchen - I believe also by relatives, not the police? Sheila wasn´t wearing knickers when she died, but she had a menstrual tampon inserted. The police didn´t gather much evidence from the house, did they? And as far as I know, they even destroyed evidence a few days after the murders (or murders/suicide, as they thought at the time. Why did they do that?
-How could Jeremy (or an accomplice or a hitman - perhaps Jeremy wasn´t there at all, but had hired a person to do it) - how could SOMEONE shoot Sheila in what must have been a very awkward position, both for Sheila and for the shooter?
-Why are so many photographs and a huge amount of case documents being withheld to this date?