After Vernon Madison’s attorneys argued in court that their client could no longer remember murdering a police officer in 1985 due to dementia, U.S. Supreme Court Justice Clarence Thomas on Thursday evening issued a temporary stay on the execution of the 67-year-old death row inmate, just minutes before Madison was scheduled to be executed by lethal injection.

Later that night, the Supreme Court announced that it had officially granted a stay in light of an eleventh hour petition for a writ of certiorari to the Alabama Supreme Court.

The Equal Justice Initiative filed the successful last-minute appeal. Bryan Stevenson, one of its attorneys, praised the intervention of Justice Thomas and the high court.

“We are thrilled that the court stopped this execution tonight,” Stevenson said. “Killing a fragile man suffering from dementia is unnecessary and cruel.”

Vernon Madison was sentenced to death for murdering Officer Julius Schulte in Mobile, Alabama. On that day, Madison’s then-girlfriend had called the police to report a missing child, the Associated Press reports. Schulte responded to the call, and as he sat in his patrol car, Madison snuck up behind the officer and shot him in the back the head.

Since Madison committed the act more than three decades ago, his attorneys say that Madison’s progressively worsening dementia and several strokes have left him legally blind, with severe memory impairment, BBC News reports.

“His mind and body are failing,” his lawyers wrote.

In 2016, after the 11th U.S. Circuit of Appeals stopped Madison’s execution with just hours to spare, the U.S. Supreme Court began looking into the case.

Although at the time, Madison’s case lacked the necessary standing to be heard in a federal court, and a 1996 statute constrains federal judges from second-guessing state court decisions, the U.S. Supreme Court issued an unsigned opinion on Madison’s case in 2017.

The Court said that Madison’s testimony indicated that the man “recognizes that he will be put to death as punishment for the murder he was found to have committed,” even if Madison does not remember pulling the trigger, the New York Daily News reports.

Now, Madison’s attorneys hope that the Equal Justice Initiative’s cert petition will convince the Alabama Supreme Court to hear Madison’s case and find Madison mentally unfit for execution.

Madison’s case raises difficult constitutional questions regarding the legality of executing inmates whose mental state may prevent them from fully understanding their guilt and punishment. The United States Supreme Court has never ruled on whether or not a convict who does not remember committing a crime can be executed.

The 2007 landmark Supreme Court case Panetti v. Quartmerman explored whether or not the execution of a mentally incompetent inmate constituted a violation of the Eighth Amendment’s prohibition on cruel and unusual punishment.

In a 5-4 decision, the majority opinion of the Court held that that death row inmates must have a “rational understanding” of not only the facts of the case, but also the reasoning for their execution. In addition, the Court mandated that death row inmates be provided the opportunity to litigate their mental competency in habeas corpus proceedings once their execution date is set.

However, in Panetti v. Quarterman, the Court left some important questions largely unanswered. Although it held that the Fifth Circuit’s analysis was unduly restrictive under Ford v. Wainwright, arguing that the state’s case rested on a flawed assumption of the legal principles articulated in this precedent, the Supreme Court did not articulate a standard by which an inmate could be judged to lack the sufficient “rational understanding” of guilt and consequence necessary for their execution to be considered constitutionally permissible under the Eighth Amendment.

In short, the Court ruled in Penetti v. Quarterman that the state had failed to give Panetti a fair psychiatric hearing that would allow him to present evidence of mental incompetence with hopes of prohibiting his execution. But the Court avoided answering one key question, which also lies at the heart of Vernon Madison’s case: What if Panetti understood the fact of his guilt, but was unable to comprehend the meaning of his punishment due to his delusions and memory problems?

Vernon Madison’s attorneys hope that the Alabama Supreme Court will draw the line that the U.S. Supreme Court has so far refused to clarify, and they are fighting to make sure Madison ends up on the better side of it.