Opponents of the death penalty are urging the U.S. Supreme Court to ban the execution of criminals who are mentally retarded. At issue is whether the execution of mentally retarded killers violates the constitutional ban against cruel and unusual punishment.

The case in question involves Daryl Atkins, a Virginia man convicted of murder in 1998 and sentenced to death. Atkins has an IQ (intelligence quotient) of 59 and is considered mildly retarded.

Even though a jury convicted him of murder and sentenced him to death, his attorneys argue that Atkins and other mentally retarded criminals do not have the intellectual capability to appreciate the depth of their wrongdoing. They argue that putting such people to death would violate the U.S. Constitution's ban on cruel and unusual punishment.

Atkins's lawyers also argue that a national consensus has emerged in recent years against executing the mentally retarded. Of the 38 states that allow the death penalty, 18 have enacted exceptions for mentally retarded criminals.

On the other side of the argument, a Virginia prosecutor told the high court that Daryl Atkins had the ability to plan and carry out a murder and that he should be held accountable for his actions like anyone else. Prosecutor Pamela Rumpz also said it would be wrong for the Supreme Court to exclude an entire group of criminals from having to face the death penalty.

Several of the Supreme Court justices said they were trying to determine whether a national consensus on the issue has emerged. When the high court last dealt with the issue in a 1989 case, only two states that allowed the death penalty had protections for the mentally retarded.

Justice Ruth Bader Ginsburg also noted that the fact that some states do allow executions of mentally retarded criminals has resulted in international condemnation of the United States from a number of countries and organizations including the European Union.

A decision in the case is expected by the end of June.