I've read through this thread, and am surprised by the limited consideration for the victim's rights.
We talk of rights, whether we believe they're natural or not, but when it comes to enforcing them, society seems to wind up scratching its collective head. If someone stole an expensive china dish, few would question his obligation to repay his debt, not to society but to the victim. Why is it that when a criminal takes something of much greater value--a human life--we speak of rehabilitation and not repayment?
Rights are not inalienable. Yes, you absolutely read that right. The very existence of government demonstrates that liberty is not inalienable, but it goes deeper than that. When a violent criminal takes a victim's life, he is basically enslaving the victim to his own will, claiming some kind of ownership over it. The problem is that that ownership is illegitimate.
Complete repayment is impossible. The human being in question did not consent to have their life taken, certainly, and given the immense (some would say incommensurable) value of human life simply by virtue of the fact that it's human, the criminal can never sufficiently compensate the victim's family for their loss.
They can demand some amount of money. They can demand limited punishment. In the end, though, we talk of the murderer's debt to "society" and leave it at that. If the criminal has claimed an innocent life as his own, then the very least we can do is allow the family to claim what is justly owed them--the criminal's life. Perhaps execution need not be cruel, but it should be sufficient to resemble some kind of repayment.
On the other hand, if the victim's family does not want to execute the criminal, they should be free to let them go with minimal punishment. We hold the victims accountable for their decisions, but we should not disallow them what is justly owed them.
A couple more points.
1.) The "eye for an eye makes the whole world blind" statement is ridiculous as popularly used. When people speak of an eye for an eye, they simply mean that the victim demands their due. If, indeed, half of the world has decided to violate the rights of the other half by taking both their eyes, then not only would that other half be justified in claiming the eyes of the violators, but the whole world would be better off. The alternative is a world of blind victims and sighted criminals. Ridiculous.
2.) "Stoop to their level?" Oh, so why are you okay with locking people in cages? Hell, for the rehabilitation folks, why are you okay with subjecting other individuals' minds to what amounts to brainwashing, forcing your values on them? Any system that exacts punishment--or, for that matter, locks anyone away--"stoops." But to compare extracting repayment from a violent criminal to taking an innocent life is senseless. They are entirely different things.
3.) There's nothing illogical about the death penalty, unless you think Kant, Locke, etc. were illogical. The death penalty has survived in part because repayment has been, for much of human history, a vital element of justice. Both sides of the debate have, and have had, reasonable arguments. There's no reason to be immediately dismissive of either one--only the stupid arguments on either side.
4.) I am indeed concerned about killing innocent people, and it is the reason
my personal opinion has wavered on the death penalty in execution. I do not always stand in the same place. A few months ago, I was adamantly against it. Now I don't see much of a different between locking an innocent man up in a cage and executing him, at least not from an ethical perspective. Either way, he can never regain the years he's lost.
I fall somewhere between conservatism and libertarianism, which means I distrust the government. But I am not an anarchist. I believe government is only legitimate so long as it protects and sets parameters for repayment of lost life, liberty, and property. If it works against those ends, or if it fails to protect and preserve, then it is at best redundant and at worst tyrannical, and best done away with. Since I support government's existence, I have to trust it to do a decent job with law and order. There is certainly no unwritten rule for small government types to oppose the death penalty on principle.
Even Rothbard didn't, and regardless of your opinion of him, you must at least concede that he was no friend of government policy.
Anyhow, in an ideal world I would always favor an option for the victim to exact appropriate punishment but also allow lenience against the offender. We do not live in that world, so I may be against the death penalty tomorrow. But I will never claim that it is unethical or that someone stoops to the level of rapists and murderers by supporting it.