PHOENIX — An Arizona jury failed to reach a verdict Thursday in the sentencing retrial of Jodi Arias after a lone juror refused to back the death penalty, a development that spared the former waitress from execution for murdering her former boyfriend.

It was the second time a jury has been unable to decide whether the 34-year-old Arias, convicted of murder in 2013, should be executed for the 2008 killing of Travis Alexander. Under Arizona law, she can no longer be sentenced to death.

“We are hung and additional time will not change this,” the foreman of the jury of eight women and four men wrote in a note read by Maricopa County Superior Court Judge Sherry Stephens, who swiftly declared a mistrial, drawing sobs from Alexander’s relatives.

The judge now has the task of deciding Arias’ punishment, and can sentence her either to spend the rest of her life in prison or to give her the possibility of parole after 25 years. The next hearing is set for April 13.

“The real justice will be in the afterlife, when Jodi burns in hell,” Alexander’s sister, Tanisha Sorenson, tearfully told reporters outside the court.

County Attorney Bill Montgomery said the jury vote was 11-1 in favor of the death penalty, and jurors confirmed one woman had been the lone holdout.

Alexander, 30, was found dead in a shower in his Phoenix-area home in 2008. He had been stabbed more than 20 times, his throat was cut almost from ear to ear, and he had been shot in the face. Prosecutors say Arias killed him in a jealous rage. She says she acted in self-defense.

Defense attorney Kirk Nurmi had shown jurors photographs of Arias in her youth and pleaded with them at closing arguments to spare her life, describing her as a remorseful and mentally ill woman who had been abused since childhood. He said no verdict could have soothed the anguish over Alexander’s death.

“I don’t think today’s victory will repair any sadness or change anything. But we hope it can begin the closure process for all those who are affected by that tragedy,” Nurmi said.

The prosecution had shown jurors a photo of Alexander with his neck slashed, portrayed Arias as cold and calculating, and said there was nothing to stop her receiving the death penalty.