It seems that some people tend to believe that the killer botched things a bit, that he had a plan and a goal in mind but that somewhere along the line things went wrong. For example, he had intended or would have wanted to remove jbr from the house. When one views the crime from this paradigm one is forced into an apologetic form of analysis. They have to invent excuses for why he didn’t do this or didn’t do that, ways to explain mistakes or errors in judgment or unplanned contingencies encountered by the killer while engaged in the commission of the crime.

He wrote the note because he was bored, fantasizing, had time to kill…
He didn’t remove jbr because he couldn’t get her through the window, she wouldn’t fit in the suitcase, there were people in the street…
He panicked when she screamed and…

He started out with one plan and changed it mid-stream due to some unforeseen circumstance.

I prefer a paradigm that tries to explain the known ‘facts’ as part of an intentional and, on the surface, at the moment of action, fully realized plan. There were no mistakes, errors of judgment or last minute alterations. The fact that the killer has been able to escape discovery and suspicion (as far as we can tell) for so long supports this paradigm. Not only has he escaped discovery and suspicion for an extended period of time many could not even be convinced of his existence. There was no intruder.