There was a very high profile case in Ontario over a decade ago. Basically, the man went into an absolute psychotic state on the travelling bus and cut the head off a stranger while everyone else on the bus ran for their lives.
A decade later, he's been released- under a lot of conditions and on a lot of medication, but people are very upset that he'd ever be free at all. In interviews, he's a very interesting person. "Regret" and "shame" aren't strong enough words.
It's a hard debate- if he was not guilty due to a medical condition, then he was not found guilty and shouldn't be in prison, certainly. But he did cut a guy's head off. Would you want to live next to the guy who did that while not in control of himself?
It's the extreme end of the situation, to be certain, but extremes are a great place to examine any system.