Richard Wolf

USA TODAY

WASHINGTON — The Supreme Court tightened its rules on capital punishment again Tuesday, ruling that Texas — the nation's leader in executions — cannot use a decades-old definition of intellectual disability to determine who lives and who dies.

The 5-3 decision was another in a series of high court rulings intended to eliminate differences in how states decide who is disabled — and therefore ineligible for the death penalty under a 2002 precedent — and who is not.

The case of Bobby James Moore was the third death penalty case to reach the court in recent months, each presenting a different issue, ranging from how sentences were determined to how those condemned should die. In Moore's case, it involved Texas' unique system for deciding who is intellectually disabled — one that is not based on the latest clinical guidelines.

Justice Ruth Bader Ginsburg issued the decision, backed by the court's liberal members and Justice Anthony Kennedy, who has sided with the liberals in past death penalty cases. Speaking from the bench, she said Supreme Court precedent does not allow for the "disregard of current medical standards."

"Adjudications of intellectual disability should be 'informed by the views of medical experts,' " Ginsburg wrote, quoting in part from the high court's 2014 ruling in a Florida case. "That instruction cannot sensibly be read to give courts leave to diminish the force of the medical community's consensus."

Chief Justice John Roberts and two conservative justices dissented, arguing that Moore failed to prove the intellectual deficits necessary for a holding that the death penalty would be a cruel punishment. "Clinicians, not judges, should determine clinical standards," he wrote, "and judges, not clinicians, should determine the content of the Eighth Amendment."

Moore's case dates back to 1980, when he shot and killed a grocery store clerk during a botched robbery. He was twice convicted, then found to be intellectually disabled, but Texas' highest criminal court overturned that finding, citing its own precedent, which is based on a 1992 definition of intellectual disability. His case now returns to Texas for further consideration.

"Today, the Supreme Court reaffirmed that all persons with intellectual disability are exempt from execution, and that current medical standards must be used to determine whether a person is intellectually disabled," Moore's attorney, Cliff Sloan, said.

The Supreme Court has tightened sentencing rules for people with intellectual disabilities since its landmark 2002 ruling in Atkins v. Virginia. Three years ago, it barred Florida from using a single, strict IQ standard to determine a prisoner's competency.

That case, Ginsburg wrote, "indicated that being informed by the medical community does not demand adherence to everything stated in the latest medical guide. But neither does our precedent license disregard of current medical standards."

She noted that Texas does not use the outdated standards in other contexts, such as assessments of students' intellectual disabilities or the diagnosis of juveniles in the criminal justice system. "Texas cannot satisfactorily explain why it applies current medical standards for diagnosing intellectual disability in other contexts, yet clings to superseded standards when an individual's life is at stake," she wrote.

Justice Stephen Breyer — who, with Ginsburg's support, suggested in 2015 that the high court consider declaring capital punishment unconstitutional — said during oral arguments that the Texas standard "would free some, while subjecting others to the death penalty."

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Kennedy, the lone conservative to voice skepticism about the Texas system during oral arguments, acknowledged that the Supreme Court's 2002 precedent barring execution of the intellectually disabled "left some discretion to the states." But he said Texas' method of determining disability seemed designed to limit who can claim it.

Texas Solicitor General Scott Keller told the court that the state goes by the Supreme Court's standard — looking at defendants' intellectual functioning, adaptive behaviors and at what age their impairments appeared. "Texas is well within the national consensus," he said.

But Sloan disagreed. "Texas is very extreme and stands alone," he said, accusing the state of using "lay stereotypes" of intellectual disability such as the character Lennie in John Steinbeck's Of Mice and Men.

Texas leads the nation in executions with 542 since 1976, nearly five times the total of runners-up Oklahoma and Virginia. Its effort to execute another prisoner despite racially biased testimony from a defense witness was blocked by the high court last month.

Nationwide, the pace of executions has slowed since peaking in 1999. There were 20 last year, the lowest number in a quarter century; there have been six so far this year, including four in Texas. The trend is a result of action by legislatures and courts, as well as problems states face getting the drugs required for lethal injections.

Despite that trend, voters in California, Nebraska and Oklahoma decided to retain or restore capital punishment at the polls in November.