To me the silencer is the one and only bit of physical evidence that is relevant.
You would say that Sheila would not use it and then put it in the back of the cupboard before using it - though if she was not in the middle of a episode it is possible - but I think she would have just taken it off and thrown it down - she would have NO reason to hide it. And why would she put it on in the first place ?
If Jeremy is innocent then I would guess it was never on the gun at all.
But the blood evidence is so confusing that I don't think most people understand it ( as verified by the expert in the last appeal )
If I was trying to help Jeremy this would be the only thing to concentrate on really that could save him .Well there are a couple of other things but they could just be rumours