Well,VHG, we are venturing into law here.In layman's terms, this man could be thought insane, and not even temporarily, because his actions are not supported or justified by any fact, but are irrational. And he shows psychopathic tendencies in being utterly cold in killing people who he regards as enemies to his cause, and in coldly giving evidence about it. But, to lawyers, his actions do not make him 'criminally insane', since he knew what he was doing and that that was wrong by any normal standards.
The first murderer I ever defended was, in law, just like that. He lured a child to a gravel pit, where he strangled her. He had , weeks before, done the same but the child survived. The psychiatrists said he (quote) "showed clear psycopathic tendencies". In interview with us, asked to describe the events, he said "as I was doing it, it suddenly started to rain, it was very cold, which was annoying". He attached far more importance to his own sudden discomfort at the time, than to anything else. Strangling a child was dismissed in brief, matter of fact terms, as though that was perfectly ordinary. Insane? Well,the lower court didn't find so, and nor did the Court of Appeal. The defence of insanity failed at both levels. He was sentenced to life imprisonment, as any normal murderer.