Just a thought. I wonder if Morgan & his flatmate were in a habit of leaving their front door unlocked for when either returned home. If Morgan had a rough idea of when his flatmate would be home that night could he have left it unlocked for her??
I was saying this in an earlier thread.. And it's something I do all the time for my housemate - I don't often lock the doors if we're all home, and I leave it unlocked if the housemate's out so he doesn't have to dig for his keys. I'd lock it if I went to bed, but not if I was up and around. I don't think Morgan was the kind of guy to worry about home invasions, so it's very possible he didn't lock the door.
Maybe something I ought to re-think, after these past few murders...
Anyway, it could have been as simple as DJK saying 'hey I go this way home, I'll walk with you' or something.. and then he tries the door later and it's open..
Personally, I think it was Morgan getting an offer to kick on a bit, seeing as he'd struck out with the girls that night.. He clearly was in a drinking mood, so it could have been 'wanna have some beers 'round home' and DJK didn't leave when he was expected to... Or slipped Morgan something from a pill bottle, which DJK very well may have had access to, and followed him upstairs in the hope of talking Morgan into sex.
I think Morgan did -something- to set DJK off, and the most likely thing I can think of is rejecting his advances, after all that effort put in to stalking...
PS: almar, good thinking about the back of Vinnie's, etc.