At the Library of Law and Liberty Dalrymple declares his opposition to the death penalty, though as usual he goes to great lengths to understand dissenting arguments, and accepts some of them:
…I am going to write about the death penalty, a subject about which almost everyone is contradictory, including me. I am against it though I am not a complete pacifist and do not believe that it is always wrong to kill, and though I happen also to believe that it, the death penalty, works – as a deterrent….
My main objection to the death penalty is that, even in the most scrupulous of jurisdictions, mistakes are sometimes made, and for the law to put someone to death wrongly is an injustice so monstrous as to undermine trust in law itself. I once used this argument in company in which someone claimed to be able to refute me easily; for it was a fact, he said, that more people had been murdered by murderers who had not been executed than who had been wrongfully executed.
Granting for a moment his empirical premise, though I was not absolutely sure that it was factually correct, I replied that his argument was valid only if one accepted a very narrow interpretation of utilitarianism: and since I knew him to be not that kind of utilitarian, he was guilty of self-contradiction. My problem was that, on occasion and if need be, I resort to precisely the same kind of utilitarian argument myself; and therefore I was guilty myself of the very philosophical inconsistency of which I accused him. My interlocutor had the grace not to mention it.