Updated at 1:45 p.m. with new information throughout

WASHINGTON -- The method Texas has used for 13 years to evaluate mental disability in death-row inmates has allowed for the execution of such inmates, violating the Constitution's prohibition on "cruel and unusual punishment," the Supreme Court ruled Tuesday.

The court ordered Texas to use modern medical standards, rather than the criteria the state now uses, which are based on medical standards from 1992, to determine whether death row inmates are fit to be executed.

The inmate at the center of Tuesday's case -- Bobby Moore, who has been on death row for more than 36 years -- will have his case sent back to Texas' highest criminal court for re-evaluation.

Although a trial judge once declared Moore intellectually disabled, noting, among other evidence, that Moore still had trouble understanding the days of the week and the seasons of the year at age 13, Texas' Criminal Court of Appeals overturned that ruling. The court agreed that Moore was disabled under modern criteria -- but fit for execution under the outdated and non-scientific criteria that the state judges preferred to use.

The justices voted 5-3 to reject Texas’ method for evaluating mental disability in Moore's case, with Chief Justice John Roberts and Justices Clarence Thomas and Samuel Alito dissenting.

Justice Ruth Bader Ginsburg, who wrote the court’s opinion, rejected Texas’ current approach in no uncertain terms.

The standards Texas uses are "an invention" of the Court of Criminal Appeals, "untied to any acknowledged source" and "not aligned with the medical community's information," Ginsburg wrote. "Accordingly, they may not be used, as the CCA used them, to restrict qualification of an individual as intellectually disabled."

For years, Texas has used a seven-part test called the Briseño standard to evaluate mental disability. The test involves a 1992 definition of disability used by the American Association on Mental Retardation as well as a number of subjective, nonscientific factors devised by a former judge. Those nonscientific factors include whether the individual's parents and friends believed them to be intellectually disabled in childhood and whether or not they seem capable of telling a lie.

The former criminal court appeals judge, Cathy Cochran, quoted the John Steinbeck novel Of Mice and Men in crafting the Briseño standards, citing the character Lennie Small as an example of someone who should be exempt from the death penalty. Since then, some critics pejoratively refer to the method she devised as "the Lennie standard."

Stereotypes

In using criteria based on Cochran's impressions of disabled people, Texas “advanced lay perceptions of intellectual disability,” Ginsburg wrote. “Those stereotypes, much more than medical and clinical appraisals, spark skepticism.”

Even Roberts, who wrote the dissent, agreed with Ginsburg that Texas' reliance on the Briseño standards was inappropriate.

"I agree with the court today that those factors are an unacceptable method of enforcing the guarantee of Atkins," Roberts wrote, citing a 2002 case that established a prohibition on executing intellectually disabled people.

However, Roberts said, it wasn't the Supreme Court's responsibility to specify that modern clinical standards must be used.

"Clinicians, not judges, should determine clinical standards," Roberts wrote.

The case began in 1980, when Moore, who was 20, was involved in a grocery store robbery in Houston. Moore shot and killed James McCarble, the 72-year-old store clerk.

Two months later, Moore was sentenced to death. But lawyers for Moore, who was still illiterate at the age of 14, argued that he was severely intellectually disabled, and made Moore's intellectual disability a major part of their appeal strategy.

In 2002, the Supreme Court banned the execution of individuals with intellectual disabilities, noting that it was a violation of the Constitution's ban on cruel and unusual punishment. The court gave broad leeway to the states to determine who qualified as intellectually disabled.

Disregarding standards

But in Tuesday's ruling, Ginsburg wrote that court hadn't gone so far as to license "disregard" of current medical standards. Ginsburg noted that Texas is willing to use current medical standards when it evaluates individuals outside of the criminal justice system, including when the state assesses students for intellectual disabilities.

"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.

Texas courts must now re-evaluate Moore under modern medical criteria.

A spokesman for Attorney General Ken Paxton said he was "disappointed" by the decision, but he declined to comment further.

Moore's lawyer, Cliff Sloan, said he was pleased the justices were willing to reaffirm that intellectually disabled individuals should be exempt from execution.

"The Supreme Court has sensibly directed Texas courts to be informed by the medical community's current diagnostic framework before imposing our society's gravest sentence," Sloan said in a statement.

The ruling in this case could open up a new avenue of appeal for any number of death row inmates who were deemed intellectually fit for execution under Texas' old standards, according to death penalty expert Jordan Steiker, a professor at the University of Texas School of Law.

An analysis Steiker worked on last year concluded that 30-40 inmates on Texas' death row would probably have strong claims of intellectual disability under the vast majority of other states' standards.

Steiker noted that even the dissenting justices agreed Texas' standards were inappropriate.

"I think that's pretty astonishing," Steiker said. "To have eight justices weigh in on what has been the Court of Criminal Appeals' approach for over a decade?"

"That's a pretty dramatic intervention," he said.