Thanks JJ and Estelle :tyou:
I'm as sure as OP shot Reeva that HvB is guilty. I'm a little fearful that he'll escape justice, he's a nasty piece of work and thinks he's so clever!
O knows what she heard and it was men arguing, 2 probably 3.
It's outrageous to think Martin would have a movie blaring loud fight scenes after 10 pm until 12 am, and on a MONDAY night, it wasn't a public holiday! Henri says he didn't hear an argument but how could he if he was watching a cinema experience of Star Trek 2?! As Tortoise posted, he wants it both ways, there was NO argument in his street on 26/27 Jan, 2015!
How convenient this happens on the night the Van Breda family is massacred! A couple of neighbours haven't lived there for a year and Mr Locke is elderly, so O stands alone having heard Martin and Rudi in their last moments alive.

O asks why HvB didn't come to her for help? Million dollar question with the emphasis on the million dollars.
At least we the public can imagine what happened. There was a fierce dispute with HvB, he's a lazy so and so, would rather kill his family then get his act together!! He has a side that is rarely seen and only his closest family have witnessed it, and they're gone except for Marli. It's a scary thought should he start his own family and they defy him.
No wonder Janine Philander was wasting time, she thought it was a prank call. I owe her an apology for my scathing remarks about her inefficiency. HvB is a classic psychopath and couldn't mask his glee in making his fantasy come true, erasing his family. I hope Judge Desai sees him for what he is and can picture correctly how that night played out. (All my opinion)