Surely Shiela's clothes woudn't fit Jeremy? Anyway a sweater is a sweater
My wife sometimes wears my sweaters. But that means I can't wear them any more because now they're OUT OF SHAPE GRRR 
It all appears to be hearsay this. I can't imagine JB wearing Sheila's knickers, can you? I mean....they would be too small and so would her bra. Jumpers and jerseys are different though. Some are definitely worn by men and women.
That photo of him when hes led away with the jumper on, he looks like hes got eye liner on so maybe he was having a bit of a dress up! anyway nothing wrong with that each to their own!
Back in the eighties there was a LOT of that going on. I met my husband in the late eighties. He had black, dyed hair and eyeliner AND mascara - it was NORMAL. Well, at least in certain circles. We also shared clothes (and still do - at least I borrow clothes from him
) And that includes jeans, yes.
Edit to add - maybe it was a bit strange that Jeremy would wear his dead sister´s clothes. I dunno! If he did kill her, it seems highly obtuse. If he didn´t, it could have been that he missed her.
Yes, that was the era of the 'New Romantics'. Perhaps JB was a fan?! Still, a bit weird to wear his sister's clothes though....
I guess people react in different ways. My lovely, fantastic sister, whom I miss every single day, passed away a few years ago. We were the same size and her husband asked me to go through her clothes to see if there was something I wanted (this was months after her passing.) He said, PLEASE do it - he didn´t know what to do with her clothes and personal belongings. But thing is, I couldn´t. I just could not - and she had some gorgeous, expensive clothes.
All I could do was sort through her make-up stuff and throw things away and keep one thing, she had never used, as a memory. I still have it - a special edition Chanel thing; but I never used it.
But I know that other people like to keep, for instance, a piece of clothing or a used pillow case, to be able to smell their deceiced, loved one.
I have no idea what Jeremy Bamber´s motives for using her clothes were; I don´t know him. But it gives me a strange feeling, I have to say. I get this thought that he was jealous of her and wanted to take over where she left - JUST speculating!!!