A former student asks how those who are both pro-life on abortion and who also advocate capital punishment can reconcile these two views. It would seem, she suggests, that to revere life would lead one to oppose all killing of human beings and that it is inconsistent to oppose abortion but not state-sponsored execution.
I think the answer is that those who are pro-life, or more precisely, those who are strongly pro-life, believe that no one has the moral right to deliberately kill an innocent person. If an unborn child is, in fact, an innocent person, which they believe it is (although its personhood is debated by philosophers), then it is morally wrong to deliberately kill it.
Nevertheless, although life is precious, its preservation is not an absolute. Killing in self-defense or in defense of others is morally permissible because the individual who constitutes a threat against you or another is not himself innocent. Killing in war, assuming the conflict meets the criteria of a just war, is morally permissible under certain prescribed circumstances because the war is a form of self-defense or defense of others. Likewise, a convicted murderer is not an innocent person and is thus not protected by the moral presumption against killing innocents.
To oppose capital punishment on the grounds that it is inconsistent with placing a high value on life is, I think, a confusion. The more serious the crime the more serious the punishment must be. A society that truly values life would surely make murder one of the most serious offenses an individual could commit and therefore the crime would merit the most serious punishment.
To decline to execute a convicted murderer on the grounds that his life is too precious to forfeit is to implicitly deny that any crime is so wicked that it merits ultimate punishment. It is to implicitly affirm that the loss of the victim's life was not so serious an offense that it is worth taking that of his killer. In other words, we're claiming that we believe life is too precious to sacrifice, but our behavior is actually demonstrating the opposite. Our unwillingness to execute a convicted murderer is a tacit acknowledgement that we don't value the life of the victim enough to make ending it a crime punishable by the most severe penalty.
We would be outraged if courts began to punish rapists by merely fining them, as is done in some Muslim countries. We would insist that this is manifestly unjust. A fine is not commensurate with the crime of violence against the victim. The law, we would argue, is devaluing women by, in effect, establishing that they aren't worth incarcerating their attackers over. It would be ludicrous to say, on one hand, that we believe women are valuable as human beings and then, on the other, treat rape as a misdemeanor. Rape is a serious offense and anything less than a serious penalty for it sends the message that women aren't valued by the society in which they live.
It really is much the same with murder. The refusal to execute a murderer actually devalues the life of his victim. Just as the promiscuous use of the death penalty would cheapen human life, so, too, would its abolition.
There may be other reasons for not executing certain types of criminals, but the argument from a consistent reverence for life seems to me to be one which, paradoxical as it may sound at first, actually cuts in favor of capital punishment.