A Texas court relied on outdated and stereotypical rationales to determine that a death row inmate who struggled as a teenager to grasp basic math was not intellectually disabled and should be executed, the U.S. Supreme Court has ruled, reinforcing that established clinical guidelines must underpin such decisions.

The justices held on Feb. 19 that the Texas Court of Criminal Appeals, the state's highest court for criminal cases, did not follow instructions issued by the Supreme Court in March 2017 when it first reviewed the proposed execution of Bobby James Moore.

The state court in June ran afoul of prior high court decisions that barred executions of the intellectually disabled and found that any determination of whether a defendant was indeed disabled had to include criteria "informed by the medical community's diagnostic framework," the opinion said.

The high court's unsigned opinion said the Texas court erred in using criteria that includes the inmate's alleged ability to show leadership capabilities and whether he could respond "rationally and coherently to questions."

"The appeals court's opinion, when taken as a whole and when read in the light both of our prior opinion and the trial court record, rests upon analysis too much of which too closely resembles what we previously found improper," the opinion said. "And extricating that analysis from the opinion leaves too little that might warrant reaching a different conclusion than did the trial court."

The Supreme Court reversed the state appellate court's ruling and sent the matter back so the court can again determine whether Moore may be executed.

The American Psychological Association, which had filed an amicus brief in the case, commended the high court for again finding that Texas sought to use "outdated means" of ascertaining whether individuals are mentally fit to be executed.

Correctly diagnosing whether someone has an intellectual disability should include assessing how an individual adaptively functions in social and practical spaces and whether deficits were present as the person was growing up, among other criteria, the association told the court in November.

"APA is pleased that the Supreme Court continued to uphold the need for modern, scientific standards for assessing intellectual and developmental disabilities, especially cases involving capital punishment," Arthur C. Evans Jr., the association's CEO, said in a Feb. 19 statement.

Moore was found guilty in 1980 of fatally shooting a grocery store clerk during a robbery, according to court documents.

A Texas trial court found he was ineligible for execution in part because of evidence such as that at age 13, he could "scarcely" understand time or know that subtraction is the opposite of addition, according to court documents. The state appellate court reversed the trial court's ruling in September 2015.

Justices Samuel Alito, Neil Gorsuch and Clarence Thomas dissented on Tuesday, asserting that the Supreme Court had previously failed to give Texas sufficiently specific instructions on how to comply with its 2002 Atkins decision banning execution of the intellectually disabled, and that the current majority goes against long standing high court precedent by delving into the specifics of the case.

"The court's foray into fact finding is an unsound departure from our usual practice," Justice Alito wrote. "The error in this litigation was not the state court's decision on remand but our own failure to provide a coherent rule of decision in Moore."

Chief Justice John Roberts, who had dissented in the previous case, on Tuesday issued a concurring opinion with the majority, writing that Texas had "repeated the same errors that this court previously condemned," such as focusing on Moore's "adaptive strengths rather than his deficits."

"That did not pass muster under this court's analysis last time," Justice Roberts wrote. "It still doesn't."

After prosecutors in Harris County agreed with Moore's attorneys that he should not be executed, the Texas attorney general's office unsuccessfully tried to take over the case, according to court documents.

"The Harris County District Attorney's Office disagreed with our state's highest court and the attorney general to stand for justice in this case," District Attorney Kim Ogg said in a statement. "The U.S. Supreme Court agreed. Bobby Moore is intellectually disabled."

The Texas attorney general's office could not be reached for comment on Wednesday.

"We greatly appreciate the important ruling from the Supreme Court," Clifford M. Sloan, an attorney at Skadden Arps Slate Meagher & Flom LLP representing Moore, told Law360 on Wednesday. "We are very pleased that justice will be done for Bobby Moore."

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