The false positive vs false negative discussion in criminal justice is the whole problem. You cannot come up with a number that is satisfactory to everyone, and for every person you lock away forever because they will surely reoffend, how many should legitimately be over-punished for their actions?

I personally think we should provide more productive activities for prisoners, so that it is not necessarily the end of their lives or contributions to society. But that is so ripe for abuse that it's useless to even start the discussion.