The strongest case against the death penalty, I have always thought, is simply that it is irreversible, and criminal justice is prone to error. The thought that an innocent man might be put to death is appalling. I don't know whether Troy Davis, scheduled to be executed tonight, is innocent, but according to what I read about recanted testimony and questionable physical evidence it I cannot believe he is guilty beyond a reasonable doubt--let alone beyond all doubt, which is the standard that ought to pertain in death-penalty cases. In 2007 the Georgia Board of Pardons and Paroles appeared to uphold that more demanding standard. Nonetheless yesterday it ruled the execution should go ahead.

The prosecutor in the case says he is sure the conviction was right. It is hard to see how he can be. And I notice that those appealing for clemency in the case are not just people opposed to the death penalty under any and all circumstances (which might call into question their claim that Davis is a special case). Read this article by William Sessions, former FBI director and federal judge.

In reality, there will always be cases, including capital cases, in which doubts about guilt cannot be erased to an acceptable level of certainty. The Davis case is one of these, and it is for cases like this that executive clemency exists.

Those responsible for clemency play a vital role in ensuring our legal system includes a measure of compassion and humanity. The death penalty should not be carried out, and Davis' sentence should be commuted to life.