The Supreme Court refused to halt Tuesday's scheduled execution of a Texas inmate who has been diagnosed as mentally retarded, a decade after banning executions of such people as cruel and unusual punishment.
Marvin Wilson, 54, had challenged his execution as unconstitutional under the 2002 decision Atkins v. Virginia, which banned executing mentally retarded people but gave states some discretion in deciding who qualified for protection.
The defendant was convicted of murder for the November 1992 killing of a 21-year-old police drug informant, Jerry Robert Williams, and was sentenced to death in April 1994.
"The application for stay of execution of sentence of death presented to Justice Scalia and by him referred to the Court is denied," the court said in an order early on Tuesday evening.
Justice Antonin Scalia handles emergency appeals from the 5th U.S. Circuit Court of Appeals, which oversees Texas.
Wilson's IQ has been measured as low as 61, below the 70 level sometimes used to delineate mental retardation.
Texas argued that the test pegging Wilson's IQ at 61 was conducted by an inexperienced intern, and that several other tests showed an IQ above 70.
The state also said it had discretion under Atkins v. Virginia to consider seven factors in determining whether someone like Wilson should be executed, including his ability to lead, his ability to lie, and whether family and friends thought he was mentally retarded.
Lawyers for Wilson countered that this allowed the state effectively to ignore the Atkins ruling by unreasonably applying "non-clinical" factors to disqualify Wilson from its protections.
Texas is the only state to use such a test, Wilson's lawyer, Lee Kovarsky said on Monday.
Wilson's lawyers also said Texas has apparently recently received evidence suggesting that Wilson was not the shooter, undermining assumptions that led to the death sentence. The Supreme Court did not address that issue.
In a separate death penalty case on appeal to the Supreme Court, Chester v. Thaler, the American Association on Intellectual and Developmental Disabilities said Texas' test relies on false stereotypes and would count only the most severely incapacitated people as mentally retarded.
Texas has conducted roughly three out of every eight executions since 1976, when the Supreme Court allowed the practice to resume after a four-year hiatus, according to the Death Penalty Information Center.
Through July 19, Texas had conducted six of the 24 U.S. executions this year.
The case is Wilson v. Thaler, U.S. Supreme Court, No. 12-5349.
(Reporting by Terry Baynes and Jonathan Stempel in New York; Editing by Stacey Joyce)