It's important to note that 'insanity' has nothing to do with any medical diagnosis. At least over here, person can be certifiably off his or her rocker and still be legally 'sane', as long as that person can a) tell right from wrong, and b) conduct him/herself in accordance with the law. (Look up MacNaughton - it sets it out better than I can in this heat.) You can believe that the gun in your hands is a banana, and that your co-worker is Adolf Hitler, but as long as you know that it's not right to aim that particular banana at Hitler and pull the trigger, you're sane.
True, but I think there's also been a slight shift - over perhaps the last quarter of a century - in what jurists mean by wilful (and often, but niot always, this implies,. legally sane) intent
. As you're touching on: intent used to be understood as "he did it knowing what his/their act was /in itself/ and understanding that it could lead to - like, death of the other, the culprit's unlawful possession of the lady's jewels, or cooked documents /larceny/ - he did that in a conscious way
, then he must have been sane." These days, intent sometimes seems to be read: "the accused wasn't just holding the gun or whatever and firing it with will, he must also have known what kind
of offence he would be making himself guilty of." I've seen people talk hemselves out of accusations of rape, deception, fraud relating to millions in cash and papers, without ever disclaiming the bare physical facts of what happened, or what was said at the time of the suspected crimes, because they were aided by their lawyers arguing the view, and the judges buying, that to really have acted with intent
, they had to have been aware of just what crime they were about to commit! So if you appear too blunt, too dumb, or in denial of the fact that you actually committed rape, fraud or forgery, then you can't be convicted of it. ("I received this outrageous sum of money from my friend for helping him to defund twenty billion bucks from the company, which it turns out later was a half-empty shell, but I never dreamt the money I got was anything other than a fee for business consultatory advice")
Not sure how much this applies to cases in the US - I would be interested - but a comparable thing would have been if the Clutter killers (In Cold Blood
) had been acquitted because it couldn't be proved that they had really acted in a deliberate wish to kill the family. After all, those four unlucky people were snuffed out at the end of a fruitless robbery, the need to get rid of eyewitnesses would have been a major reason, and the court never managed to establish beyond doubt who actually killed each particular victim. If (just as a thought experiment) the court had found that Smith and Hickock might have acted ina sudden psychosis or panic, and were not really aware that the four would die if they were shot, plus the court were not sure hwo had pulled the trigger, then they muight conceivably had gone free on the counts of murder or manslaughter. Of course, in 1960 they didn't really bother with mental investigations for ordinary murder cases, and nor were they used to defendants simply sitting through an entire murder trial and saying blandly "I don't remember a thing..." or "I was so high, I really don't think that's me in the CCTV picture and I don't recall being in that place at the time."