The death penalty should be opposed in all circumstances.
I believe that the right to life is the cornerstone of human rights. It can therefore never legitimately be the purpose of the state to take life. There are of course cases where human life is taken as the consequence of other legitimate policies: e.g. the waging of a just war, a police operation to free a hostage, self-defence, etc. but in all these cases the loss of life is the consequence of the action, never its purpose.
It is from the protection of human life (even of evil-doers) that all other rights derive. (NB there are 12 US states which have no death penalty, so the US is not all bad on this issue.). No European country (except the dictatorship in Belarus) has a death penalty, nor does Canada, Australia, or New Zealand.
Of course there are practical arguments against the death penalty: it’s irreversible in the event of mistake, it focuses attention on the criminal and not the victim, it equates the crime and penalty and therefore tells the criminal “yes’ you can kill, if you don’t mind dying, etc. But my fundamental objection is not practical but moral.