But the mental illness is somehow proved, isn't it ? Is it a consequence of Anni's murder or was he already mentally ill before ?
It's a good question isn't it. I can't find anything offical written about his mental state before all this happened.
Certainly it is believable that the stress of the events in South Africa and their aftermath could have resulted in post-traumatic stress disorder and depression (which is what certain doctors have diagnosed). He has also been given different medications for the depression, some of which have had an adverse effect.
If we also consider the fact that by all accounts for the years preceding his marriage he was engaged in a secret homosexual life and at great pains to cover the fact up for fear of disgracing his family, we have something that would have caused a build up of anxiety over the years that could easily end up having a severely detrimental impact on his mental state. (This issue has been written about extensively from Freud til today). Added to which, in this case, intimate details of his past and the fact that he was covering it up are now in the public domain, which must cause him considerable discomfort.
If he DID kill his wife (no conclusive proof yet, of course) it demonstrates what a narcissist he truly is - entrapping Anni for the purpose of being seen to have an attractive woman by his side, then getting rid of her when she began to realise that all was not well in the bedroom. This is full-blown Narcissistic Personality Disorder to its utmost extent - the person goes as far as to kill if the other party doesn't fit into their picture.
Such a narcissist would typically focus on his own traumas with regard to the situation, and this is exactly what we are seeing now, with attention being placed on his mental anguish and the problems he would be likely to face in a South African jail, to the exclusion of any consideration for the concerns for his late wife's family; and also to the temporary exclusion, if he is arguing that he his innocent and that therefore others are guilty, of any path toward justice being embarked upon by the court.
A pretty disturbed person. So it is likely that when his lawyers are playing the mental illness card they happen to be speaking the truth - and underlining his narcissism and extending the legal process along with it.