Conversation so far:
Why was there an assassination attempt on Hendrik Verwoerd?
David Pratt claimed he had been shooting 'the epitome of apartheid'. However, in his defence, he stated he only wanted to injure, not kill, Verwoerd.
Why did David Pratt want to hurt Verwoerd in any capacity?
The court accepted the medical reports submitted to it by five different psychiatrists, all of which confirmed that Pratt lacked legal capacity and could not be held criminally liable

Question: Why couldn't he be held liable?
Self-contained rewrite: Why couldn't Pratt be held liable for the attempted assassination on Verwoerd?