What's done can't be undone

Many of those opposed to the death penalty argue it's wrong to wrongfully execute an innocent person, because death would be an injustice which could never be undone. Short of a miracle, it's not as if the innocent person can be raised from the dead.

Of course, I trust most if not all of those on the opposing side would entirely agree it's wrong to wrongfully execute an innocent person. I take it we'd be agreed here.

However, is the fact that death is an injustice which cannot be undone when carried out against an innocent person (or any person) a good reason to oppose the death penalty?

If it is, then why not oppose lesser punishments in our legal system as well? After all, surely there are many wrongful punishments meted out against innocent persons in our legal system, and surely many if not most of these punishments cannot be undone once they've been administered.

Indeed, wouldn't it be generally wrong to wrongfully punish an innocent person, even if the punishment is less than death? Say someone has been wrongfully imprisoned for a year. Financial or perhaps other restitution might be given to the wrongfully imprisoned person. But it's still a year of freedom he or she can never get back. This, too, cannot be undone.

But let's say the person who is against capital punishment bites the bullet and argues we should do away with lesser punishments for this reason. If so, then what sort of a legal and penal system would we have left? There wouldn't seem to be much of one left, for it would seem to rule out punishing many if not most crimes.

Finally, I think there might be some tension (albeit perhaps a tension which could be relieved) for those who are against capital punishment for this reason but in favor of euthanasia, for it's possible the person who euthanizes themselves may come to regret the decision in the future if it were somehow possible for them to choose again. But, of course, it wouldn't be possible.