Nobody's saying that he shot her for eating in middle of the night, right? His nasty bullets, Her munchies, his arrogance & occasional temper outbursts, etc: None of that is meaningful to me. None of it points to premeditated murder (as I understand premed murder). I still haven't heard a motive for this being premed murder that rings true. I suppose this will get decided on forensics instead.
Does manslaughter (murder by carelessness leading to a significant jail sentence) exist in South African criminal code? The SA legal code can't be so lax as to say that you can shoot any suspected intruder with zero threatening actions by them and go scot free (is it?!)
Judge sitting as sole decider (no jury) can happen in American criminal cases. It's preferred by the defence in cases exactly like this where motivation and technical points of law are very crucial to the verdict between 1 of 2 serious outcomes (such as manslaughter vs. 1st deg murder).