I suppose that good people can make a[singular and non-violent] mistake or error in judgement which can run them a foul of the law. These people don't require reform. They are typically leaniently sentenced, pay for their mistake and move on.
I also suppose that others are more habitually and fundamentally anti-social. These people are not worth the effort of trying to 'save'. The brains have literally been wired for this behavior[over the course of many years]. They must be removed from society.
There are also those somewhere in between natural-born killer and 'busted for pot'. These people are responsible for their own personal choices. If they keep making bad choices of their own volition I have no compassion for them. [I say this from first hand experience dealing with a close relative who is a lifelong fuck-up.]