The Texas solicitor general urged the U.S. Supreme Court during oral arguments Wednesday to overturn a decision allowing a death row prisoner's successive habeas claim for intellectual disability under new diagnostic standards, saying the challenge did not qualify for a rare exception under the Antiterrorism and Effective Death Penalty Act of 1996.

AEDPA generally bars state prisoners from filing successive habeas applications. In this case, prisoner Dexter Johnson filed a successive application raising a claim under Atkins v. Virginia , a 2002 high court decision that holds that executions of people with intellectual disabilities violate the Eighth Amendment's prohibition on cruel and unusual punishments. Johnson contended that he could not raise the claim in his first habeas petition because he did not qualify as intellectually disabled under earlier criteria.

Wednesday's arguments focused on whether Johnson's claim falls under a rare exception for those who rely on "a new rule of constitutional law, made retroactive to cases on collateral review by the Supreme Court, that was previously unavailable," and how courts should handle changing medical and scientific definitions of intellectual disability.

Solicitor General William Peterson told the justices that the Atkins rule is not new because it was decided before Johnson's conviction and was thus previously available to Johnson, even though it would not have been successful under the diagnostic standards of the time. Peterson said updates to the Diagnostic and Statistical Manual of Mental Disorders — the industry standard reference guide — "can provide new factual predicates for claims" but did not constitute a change in the law.

"Why is the DSM a fact?" Justice Elena Kagan asked. "Why isn't it part of the law? In other words, when Atkins was announced, we made clear that there was — it was going to be based in large part on psychological criteria that were developed under the DSM. You know, it was clear that it was going to evolve. ... So why think of it as factual matter rather than the thing that provides in — at least in large part — the legal standard and was contemplated in just that way?"

Peterson replied that the high court's 2014 opinion in Hall v. Florida , which ruled unconstitutional hard IQ score cutoffs for intellectual disability determinations in Atkins cases, highlighted a distinction between the legal determination of intellectual disability and a medical diagnosis. And the high court's 2017 opinion in Moore v. Texas held that states must use modern medical standards to make intellectual disability determinations.

In Johnson's case, a jury found him guilty of capital murder in 2007 for kidnapping, raping and murdering a woman. He was 18 at the time of the killing.

Johnson's defense had presented expert testimony that he had the intellectual functioning equivalent to a 10-year-old, but the expert said Johnson did not have an intellectual disability based upon the diagnostic criteria at the time because his IQ was higher than 70.

This made a claim under Atkins impossible then, and Johnson's court-appointed counsel did not raise an Atkins claim in state habeas proceedings, according to court documents. Texas' highest criminal court, the Court of Criminal Appeals, affirmed his conviction and sentence and denied his initial state habeas petition. The U.S. Supreme Court denied his petition for certiorari.

In 2011, Johnson filed a federal habeas petition that also did not raise an Atkins claim or assert an intellectual disability. But while the petition was pending, in May 2013, a new edition of the Diagnostic and Statistical Manual of Mental Disorders — the DSM-5 — was published.

The manual contained changes that reflected a new recognition that those with IQ scores over 70 could still be intellectually disabled.

The federal court denied Johnson's petition in August 2013. The Fifth Circuit affirmed, and the U.S. Supreme Court denied certiorari again.

Johnson was scheduled for execution in May 2019. Months beforehand, the district court appointed the Federal Public Defender to represent Johnson after he raised concerns about his attorney.

Two weeks before his execution date, he filed a state habeas application raising an Atkins claim based on an evaluation performed by a new expert. The doctor found Johnson had an IQ score of 70 and qualified as intellectually disabled.

But the Court of Criminal Appeals tossed his application a week later, saying the new Atkins claim should have been raised in the earlier petition. The next day, though, a federal judge stayed Johnson's execution over the public defender's concerns about his counsel.

His new public defenders filed another state habeas petition raising an Atkins claim with additional evidence, including a comprehensive forensic neuropsychological report and other testimony and evidence that was not included with the previous filing. The state courts dismissed the petition.

Johnson's attorneys also sought the Fifth Circuit's authorization to file a successive federal habeas application. The Fifth Circuit allowed the filing and granted a further stay of execution.

In 2022, a federal district court found that Johnson met AEDPA's successive-petition requirements and allowed his Atkins claim to go forward.

The district court certified one of Johnson's questions for interlocutory review: Whether there can be judicially created exceptions to 28 U.S. Code Section 2244(b)(2)(A).

The Fifth Circuit accepted the appeal last year and reaffirmed its 2017 holding in In re: Cathey , which holds that AEDPA's "previously unavailable" rule requires courts to explore whether the claim could have been meritorious at the time of the earlier federal habeas proceedings.

Texas filed its petition for certiorari in January, telling the high court that circuits are split over when to consider when new rules were actually available in habeas cases.

On Wednesday, Johnson's attorney, Jeremy Schepers of the Office of the Federal Public Defender, argued that Atkins is tied to evolving clinical criteria, and so updates to the DSM are part of the legal standard. A change to those standards may shift the definition of the Eighth Amendment's protected class of people with intellectual disabilities.

In this case, the Atkins rule was not available to Johnson until the update, Schepers argued.

"In contrast, the petitioner and the United States assert that a rule is available simply when it's been announced," he said. "But existence and availability aren't the same thing. Many things exist that aren't necessarily available to us."

Texas is represented by Ken Paxton, Brent Webster, William Peterson, William Cole, Cameron Fraser and Gwendolyn Vindell of the Office of the Texas Attorney General.

Johnson is represented by Jason Hawkins, Jeremy Schepers, and Joe Hamrick of the Office of the Federal Public Defender.

The United States is represented by Emily Ferguson of the U.S. Department of Justice.

The case is Eric Guerrero v. Dexter Johnson, case number 25-1003, in the Supreme Court of the United States.

--Editing by Dave Trumbore.