Peter Hyatt, a statement analyst who trains law enforcement officials, explains how a liar will often build a narrative, to sell you the lie. It's information that is inserted in a statement which isn't relevant to the event, and is there to get you to think this is a nice person and buy into the narrative that they didn't do what they are accused of doing. Anyone interested can see his interviews on youtube.
He gives the example of a children's story which opens with a line like - it was just an ordinary day... The child listening knows it wasn't just an ordinary day, because it's there as a prelude to something extraordinary happening, and knows the first line is a deception.
Henri starts his plea statement with "There was nothing out of the ordinary the evening before the attack."
From this we can discern that something out of the ordinary did happen that evening. That is why he has a need to speak about it and sell a narrative. People speak of things that occur, not things that didn't occur. Why start with 'nothing unusual (that could have been a reason for me to kill my family) happened 9 to 10 hours before my family was attacked'? You wouldn't start a witness account of an armed bank robbery by explaining what you ate for breakfast 3 hours earlier. If that's all he was - a witness to the crime. He would start by saying I'd been on my laptop in bed and at about 3am I got up to use the bathroom. Rudi was asleep..
So we know something happened that evening, because he had nothing of relevance to the crime to tell, but he mentioned it anyway, so he is bringing the relevance of the evening to our attention. I think of it like this - it was not necessary for there to have been a family fight that evening, for him to formulate a plan to kill his family. He could have formulated a plan that day or a week earlier. The fact he focuses on the evening means that time frame was relevant to him. If he'd seen a shadow or heard a dog bark or seen a stranger lurking in the garden that would have made the evening relevant to mention. His account of wine and dinner and watching a film are there to sell his lie. Truth doesn't need selling, it doesn't need hearts and flowers.
Pistorius did the same. He gave an hour by hour account of the evening before, which had no obvious relevance to his story of being asleep and waking up at 3am. We see the relevance - it's a sales pitch. The question to ask is why do they need one?
I think Desai will find it is no coincidence that HvB just happened to be the only family member who was still awake 4 hours after they went to bed, and left his bed at the exact moment the axeman struck. That is some timing there!