Bamber may have felt confident Julie would not go to the police. He had spent a month telling her how watertight he was.
If she did go to the police, she would not be believed as he believed there was nothing tying him to the massacre. The police would dismiss her once she brought up MM.
Actually, this is a fair point, but if you stop and think about it, another way of interpreting what you are saying is that her evidence was of no probative value in the first place. This is the paradox with Julie. Her evidence was, in my view, an attempt by the prosecution to sway the jury emotionally. She didn't convey anything that actually proves Jeremy did it.
Why didn't one of these friends/housemates rush to the police as soon as she spilled the beans? Do you really think I would have invited a mass murderer to my 21st. birthday party? Would you?
"Oh hello, Jeremy! Everybody! It's Jeremy!!"
"Hey, nice one Jezza - you really socked it to Sheila!"
"Do you think you'll get caught, Jeremy?"
I mean, honestly, what sort of conversation are you supposed to have with Julie or Jeremy in those circumstances? Why weren't the police alerted? Why isn't there a record of Stan Jones rushing round to Julie's and demanding to know what the hell has gone off? In fact, when you take into account the 3 a.m. phone call, you have to ask: why didn't they arrest her?
Surely the conclusion has to be that they didn't take what she was saying very seriously. Young women do come out with all sorts of nonsense and the police know this anyway, but if she was imparting this information to this Battersby woman, or especially one of her male friends, surely the police would have been informed if it was actually being taken seriously?
Then there's the absence of any mention of the silencer from her evidence. If 'Matthew' (i.e. Jeremy) used the silencer, it would be one of the first things he'd mention to her when relating this exciting tale. After all, what has Jeremy got to fear? The police have missed the silencer, and according to you, Jeremy thinks he's got away with it.
Maybe Jeremy missed that part out thinking it might then eventually lead the police to a specific item of evidence if Julie turned on him, but couldn't Jeremy have just hidden that silencer when he took back the keys to the farmhouse and swopped it out for another one that was clean? Oh wait, he didn't take the keys back, did he. He let the relatives have the keys and access to the crime scene, the gun cupboard and the silencer.
I am sorry, but I remain sceptical.