Still think it's a cop out.
Isn't mental incompetence no longer a defense? And Cy's plea was in before the change?
I'm not aware of any change in the law that prevents people claiming mental impairment and I would be shocked if that had happened in SA.
Essentially, although he admits to the act, the court has found that he was not in full control/was unaware that what he was doing was wrong.
Maybe the change in law you are thinking of is that of provocation? Which was used in instances of domestic violence and other matters where someone would be acting irrationally/hot headed.