WASHINGTON — Thomas Arthur’s luck finally ran out late Thursday night on his eighth date with Alabama’s lethal injection gurney.

The Supreme Court denied Arthur’s last-minute petition seeking yet another reprieve with just minutes to go before he would have survived to fight another round in court. As a result, the aging Arizona prisoner was executed at 12:15 a.m. CT for a 1982 murder he claims he did not commit.

Justice Sonia Sotomayor dissented from the court’s otherwise unsigned decision to allow the execution to go forward. She said his lawyers should have been allowed to take a cellphone into the witness area so they could alert the courts if anything went wrong with the lethal injection, as it has in the past.

“When Thomas Arthur enters the execution chamber tonight, he will leave his constitutional rights at the door,” Sotomayor said.

The justices had dealt with Arthur before, most recently in November, when they granted his seventh stay, and in February and March, when they refused to hear his request for a firing squad rather than a lethal injection. Two justices dissented then and said Arthur faced the potential for “intolerable and needless agony” during his execution.

Now in its 35th year, the saga surrounding Arthur’s three trials and eight execution dates for the point-blank shooting of Troy Wicker in Muscle Shoals, Ala., had become an object lesson for both sides in the national debate over the death penalty, in steady decline since 1999.

“Thirty-four years after he was first sentenced to death for the murder of a Colbert County man, Thomas Arthur’s protracted attempt to escape justice is finally at an end,” state Attorney General Steve Marshall said. “Most importantly, tonight, the family of Troy Wicker can begin the long-delayed process of recovery from a painful loss.”

Rather than life in prison without parole,…