When the Supreme Court reinstituted the death penalty 35 years ago, it did so provisionally. Since then, it has sought to articulate legal standards for states to follow that would ensure the fair administration of capital punishment and avoid the arbitrariness and discrimination that had led it to strike down all state death penalty statutes in 1972.

As the unconscionable execution of Troy Davis in Georgia last week underscores, the court has failed because it is impossible to succeed at this task. The death penalty is grotesque and immoral and should be repealed.

The court’s 1976 framework for administering the death penalty, balancing aggravating factors like the cruelty of the crime against mitigating ones like the defendant’s lack of a prior criminal record, came from the American Law Institute, the nonpartisan group of judges, lawyers and law professors. In 2009, after a review of decades of executions, the group concluded that the system could not be fixed and abandoned trying.

Sentencing people to death without taking account of aggravating and mitigating circumstances leads to arbitrary results. Yet, the review found, so does considering such circumstances because it requires jurors to weigh competing factors and makes sentencing vulnerable to their biases.