He was also a strong opponent of the death penalty.

"The principles to which Beccaria appealed were Reason, a contractarian understanding of the state, and, above all, the principle of utility, or of the greatest happiness for the greatest number. Beccaria had elaborated this original principle in conjunction with Pietro Verri, and greatly influenced Jeremy Bentham to develop it into the full-scale doctrine of utilitarianism.

Apart from condemning the death penalty (on two grounds: first, because the state does not possess the right to take lives; and secondly, because capital punishment is neither a useful nor a necessary form of punishment), Beccaria developed in his treatise a number of innovative and influential principles: punishment had a preventive, not a retributive, function; punishment should be proportionate to the crime committed; the certainty of punishment, not its severity, would achieve the preventive effect; procedures of criminal convictions should be public; and finally, in order to be effective, punishment should be prompt."