The problem with the 'not criminally responsible' judgement is that it allows the state to do this
1) Criminal is found NCR and sent for treatment
2) Treatment is expensive and mad people may well appear sane if they're watched 24/7 and forced to take their meds
3) The doctors, for whatever reason decide they're sane enough to be released
4) They get released. At this point they're not watched 24/7 and don't take their meds
5)
They change their name and slip off the radar
If people just went to prison for 10 years it would cost the state more but at least they're off the streets and not able to kill anyone outside prison.
It's typical technocratic bollocks to be honest. I remember when this 4) happened and pointing it out to Canadians and them saying 'Well you're not a mental health expert, I'm sure the experts know what they're doing when they said he was safe to release'. The implication being that criminal justice policy is best left to experts, even when those experts release someone like Vincent Li after a couple of years pronouncing them 'cured'.
And like the gender self ID laws it's all very exploitable by psychopaths. E.g. murder someone while acting conspicuously crazy, then act conspicuously sane when in mental hospital, get out, change your name and you're off scott free. It's also worth pointing out there are mental illnesses which have been described as '
the quintessence of evil' and are at present incurable and untreatable. I.e. people with them are much better described as 'bad' rather than 'mad'. But we have public intellectuals like Sam Harris, who really ought to know better, claiming that all evil is caused by sickness and a
sufficiently advanced mental health system should be able to treat it. Even if you believe that is the case, our mental health system is not sufficiently advanced and we have no idea how to treat things like malignant narcissism.
IMO, and it's probably controversial, a medical treatment for things like malignant narcissism raises 'Clockwork Orange' like questions.
https://en.wikipedia.org/wiki/A_Clockwork_Orange_(novel)#Title
Alex, the antihero of 'A Clockwork Orange' was a horrible psychopath before his treatment, but that doesn't necessarily mean his treatment is something we should approve of. Burgess, who was a Catholic, most certainly did not. Messing with free will touches on things like
theodicy.
It could be argued that in a liberal society prison should be used to punish people for acts they commit, not try to reach into their head and take away the choice to commit those acts. The notion that there are 'no bad people, only mad people' is simultaneously too liberal and not liberal enough because it makes us strive for something like the Ludovico technique of 'A Clockwork Orange' which can reach into peoples' heads and take away their choice to be evil. That really does open up a can of worms. What if the state decide to punish people for 'hate crimes' with a similarly invasive technique?
The Soviet Union famously
classified dissidents as 'mentally ill' but at that point the primitive state of psychiatry meant that there was no treatment for not approving of Marxism Leninism. A society like the USSR but with access to cures for things like malignant narcissism would surely be tempted to use it on political dissidents. Even in the formerly liberal West there is an increasing tendency to classify disagreements with conventional wisdom as 'phobias' and to criminalise them. When you get sentenced for hate crime in a future UK, you may well end up being 'treated' in hospital rather than simply punished by prison. Give me prison over hospital any day!