Okay, I keep coming back to this and reading so I'll just say this, as it's on my mind and keeps bugging me and no one else has said it (I think)
You know in the cross examination, he said he went out, well he was bored and went out at least once before he finally ended up in her flat.
I'm just thinking, he knew her boyfriend was going to be away, maybe he didn't know what time she would be getting home from work, but the way he describes his actions after he got bak from work, well it almost sounds like he was anxious, unsettled, kept going out short distances for no reason (to take pics of the snow - yes well, and he hasn't any because it was 'dirty') so I think from this that he was waiting for her to get back. He kept going past her window, she wasn't back yet, he went indoors again.
WHY keep going out like that. I think he intended to catch her attention and go round if he possibly could.
I don't know why he might have wanted to, but either he wanted to spend time in her flat with her or he had other ideas already.
I think that he might have been fantasising about something like this for quite a while...have they looked at his computer history from BEFORE he killed her? I imagine that's all been deleted.
Sorry, this is pure supposition and might be way off. It's just, when I was young, I fancied one of the boys who lived round the corner and the number of times I went out for 'no reason' was outrageous...I am finding myself identifying with this behaviour, a lot of the things he says resonate with that sort of stalking mentality which I myself was kind of on the edges of as a teenager. (embarrassingly)
I think he was very excited about Joanna coming home on her own.