The court said it will hear an appeal by North Carolina death-row inmate Ernest McCarver, whose execution the justices halted this month just hours before he was to be put to death.
The justices are scheduled to hear arguments Tuesday on a case involving a Texas death-row inmate whose lawyers say he is mentally retarded and has the mind of a 7-year-old. However, the justices are not being asked in that case to decide whether the Constitution prohibits executing the mentally retarded.
In the Texas case, Johnny Paul Penry's lawyers contend jurors who sentenced him to death for murder did not have the chance to properly consider his mental capacity. The Supreme Court used Penry's case in 1988 to rule that the Constitution allows the execution of mentally retarded killers, although the court threw out his first conviction.
McCarver, 40, was convicted of the January 1987 stabbing and choking death of Woodrow Hartley, a 71-year-old worker at the Concord cafeteria where McCarver had worked.
McCarver's lawyers say he is mentally retarded and has the mind of a 10-year-old child and reads at a third-grade level.
His appeal asks whether ``national standards have evolved such that executing a mentally retarded man would violate'' the Constitution's 8th Amendment ban on cruel and unusual punishment.
Thirteen capital-punishment states prohibit execution of the mentally retarded, his lawyers said. Another 12 states do not have capital punishment.
Lawyers for the state said considerable evidence showed that McCarver was not mentally retarded, but that even if he was, his execution would not violate the Constitution.
The Supreme Court halted McCarver's execution on March 1 after he had been served his last meal. Hours earlier, North Carolina Gov. Mike Easley had denied his clemency petition.
McCarver's most recent IQ test, arranged by the defense team, pegged his score at 67, but his IQ was measured at between 70 and 80 before his 1988 trial.
In denying clemency, Easley said McCarver had planned and orchestrated Hartley's murder and was motivated by revenge against a former co-worker. He said McCarver was competent enough to gain employment and earn driving privileges, and that no court had found him incompetent.
Defense lawyers had asked Easley to commute McCarver's sentence to life in prison.
The case is McCarver v. North Carolina, 00-8727.