However, what's wrong with retribution? If my daughter was raped and murdered, how should that person be 'rehabilitated?' My daughter would still be dead and the criminal would be able to resume his life. That isn't fair by any definition.
You can accept that, adjust your goals and move forward or deal with the inevitable frustration and anger of being unable to get vengeance for the rest of your life.
On that view, it's generally just right to reward people for good and punish them for evil. Consequences -- even grand ones like balancing the cosmic scales of justice -- don't enter it.
For the same reason the severity of the sentence should be driven by the aversion of the society to the crime committed more than considerations on what will happen to the criminal after the sentence has been executed.
Punishment and rehabilitation are just parts of achieving the goal: Punishment tries to prevent further crime, both by the person being punished, and people that know what will happen to them if they are caught. Rehabilitation is great when it succeeds: Sending a rapist out to do more raping isn't so great.
All of our policies about punishment, rehabilitation and enforcement quality are tradeoffs, and the question is what's the best tradeoffs. The biggest one, IMO, has little to do with the size of the punishment (they are all pretty big), but with deterrence. Nobody is going to stop killing someone because they'll "only" get 15 years in jail. 15 years in jail is horrible for most people that aren't living in terrible conditions outside. The real kick is in chances of getting caught. The criminal believes that he won't get caught, so the size of the punishment is not necessarily that relevant, other than in keeping the person that committed the crime away from doing the same again outside of jail (crime vs other immates happens!). Improved enforcement quality, and making sure that people just don't even want to do criminal things, regardless of the punishment, is where it's at.
The problem with that is that enforcement itself is a tradeoff: We could do a lot to prevent crime in NYC if 25% of people were in some form of law enforcement (including policing the police), but it'd be a tradeoff we'd all be unwilling to make, because it'd be very wasteful.
So it's nowhere ear as simple as you paint it.
The goal is peace. It has to be peace. You might never reach that goal entirely but you can try and you want people that ensure peace exists and people that restore it once it has been violated.
Quite clearly exerting vengeance through the justice system is not the best way to achieve that goal, in fact it's obviously by far the worst.
That's why from feudal to modern societies, the Lord / King / Judge renders justice. The system becomes just again by the retaliation being decided and executed by a higher form of authority.
If someone beats me up, and we both go in front of the judge and the judge decides to do nothing because of some procedural reason or because doing nothing would benefit some greater social good, this is the very definition of injustice.
I am not saying that a justice system shouldn't care about rehabilitating criminals after they serve their sentence, but that negating the punitive role is negating the very reason why the justice system exists and is accepted.
That means justice is combination of deterrence and rehabilitation to a. discourage behaviours that are detrimental to society as a whole and b. to ensure that the offender ceases that behaviour and becomes a productive member of society again.
'Punishment' can play as small or as large a part in point (a) as you want, but the more you make it a large part of (a), the less success you will have with point (b). And failing at point (b) means you effectively fail point (a) - ie offenders coming out of the justice system who can't integrate back into society often reoffend.
Americans are a scary people.
Per capita you incarcerate more people than any other major country (developed or not).
There is also a quote of Gandhi I cannot find. So I'll paraphrase: If you are angry at someone, and he did not intend to hurt you, you should not be angry. If he did intend to hurt you, he is not as wise/it's in his nature, and you should not be angry.
If we follow your logic it is. Retribution would only serve the British girl but not the community. The community has nothing to gain from punishing the prince but everything to loose from loosing all these Saudi contracts. If you think justice is only about serving the community, not about retribution then you will happily approve the decision of the court. My personal position is that it is the very negation of justice, and that behaving this way jeopardize the acceptance of the judicial system by the population.
As for Gandhi, it's similar to the Christian "if someone slaps you on one cheek, turn to them the other also". But I am not sure that a recipe that worked well against a democratic British parliament will work as well when facing a violent thug.
What? Why shouldn't I be angry if a fool intentionally hurts me?
The way people are treated shouldn't be based on what the most emotionally invested people want. What makes the person rehabilitated is that they don't do the crime again, and nothing else. You can't cause wrongdoing to someone who is dead, so the only downside to releasing the person is you might feel sad. Only if you dwell on it for the rest of your life. But you won't, people move on.
And you think it's an indictment on Biblical (and, apparently, also Oxonion) definitions of "fair" that they'd disagree with you on that?
"Just or appropriate" doesn't actually say anything about what should be done in a case of rape+murder. Who's to say life in prison is appropriate? I don't think it is. It's a waste. The young lady wasn't put in a hellish environment for a lifetime. And what do we as a society gain by wasting money on prisoners for exactly zero return on investment? We're basically punishing ourselves to spend that money. Better to wait until the problem is solved (i.e. we don't think they'll do it again) and let them out where they can do something useful.