TALLAHASSEE — Attorneys for condemned killer Frank Walls have gone to the U.S. Supreme Court in a last-ditch attempt to prevent his scheduled Thursday execution.

The attorneys Monday filed a petition and a motion for a stay of execution after the Florida Supreme Court and a panel of the 11th U.S. Circuit Court of Appeals in recent days refused to halt the execution.

Walls, 58, was convicted in the July 22, 1987, murders of Edward Alger and Ann Peterson, who died of gunshot wounds after Walls broke into their Okaloosa County home, according to court documents. If the execution is carried out, he would be a record 19th inmate put to death by lethal injection this year in Florida.

Monday’s filings at the U.S. Supreme Court focused, in part, on arguments that Walls should be shielded from execution because he is intellectually disabled and that the Florida Supreme Court has not properly addressed the issue. The U.S. Supreme Court has held that executing intellectually disabled people violates the Constitution’s Eighth Amendment ban on cruel and unusual punishment.

“The record is rich with evidence of Mr. Walls’ intellectual disability,” his attorneys wrote in the petition Monday. “Not only does Mr. Walls have qualifying IQ scores, but there is also evidence of his subaverage functioning and issues with adaptive functioning. This (U.S. Supreme) Court should not ignore this evidence.”

But in a filing this month at the Florida Supreme Court, state Attorney General James Uthmeier’s office disputed that Walls is intellectually disabled.

“Walls is not now intellectually disabled and never was,” the state’s lawyers wrote.

The petition filed by Walls’ attorneys is more nuanced than simply whether he is intellectually disabled and involves a series of court decisions.

In 2014, the U.S. Supreme Court, in a case known as Hall v. Florida, rejected part of the state’s tests for determining whether defendants have intellectual disabilities. That part set a cutoff score of 70 on IQ exams to determine if people were intellectually disabled. The U.S. Supreme Court said the state could not use such a “rigid rule.”

In the aftermath of that decision, the Florida Supreme Court in 2016 ordered a hearing to determine whether Walls was intellectually disabled. But justices in 2020 reversed course on an earlier stance and said the Hall v. Florida decision should not retroactively apply to older cases — such as Walls’ case.

A circuit judge in 2021 rejected arguments about Walls being intellectually disabled, and the Florida Supreme Court later turned down an appeal based on the retroactivity issue, according to court documents.

Walls’ attorneys said the inmate, who had IQ scores of 72 and 74 in tests as an adult, has repeatedly raised intellectual-disability issues.

“Yet an amalgamation of wrongly decided state court precedent and convoluted procedural hurdles have thus far prevented a merits-determination on whether Mr. Walls is categorically prohibited from being executed,” the U.S. Supreme Court petition said.

The petition also said the Florida Supreme Court’s “treatment of Mr. Walls’ intellectual disability claim showcases why it is imperative for this (U.S. Supreme) Court to clarify that the Constitution’s shield against the unacceptable risk of executing an intellectually disabled person extends across every stage of a defendant’s case.”

Attorneys for the state had not filed a response as of Tuesday morning, according to a U.S. Supreme Court online docket.

Gov. Ron DeSantis on Nov. 18 signed a death warrant for Walls, who likely would be the final inmate executed this year in the state. The previous modern-era record for executions in a year was eight in 1984 and 2014. The modern era represents the time since the death penalty was reinstated in 1976, after a 1972 U.S. Supreme Court decision halted it.