PHOENIX (AP) — An Arizona prisoner is scheduled to be executed by lethal injection in less than three weeks for killing an 8-year-old girl, marking the second condemned man to decline lethal gas since the state refurbished its gas chamber — a method of execution that hasn’t been used in the United States in more than 20 years.

Frank Atwood declined to pick a method of execution when corrections officials asked him if he wanted to die by lethal injection or the gas chamber. Lethal injection is Arizona’s default execution method when condemned prisoners refuse to make a selection.

Clarence Dixon, who earlier this month became the first prisoner to be executed in Arizona since July 2014, also had refused to make a choice on his execution method.

The last lethal gas execution in the United States was carried out in 1999 in Arizona, which refurbished its gas chamber at the prison in Florence, southeast of Phoenix, in late 2020. The state also had purchased materials to make hydrogen cyanide gas, which was used in some past U.S. executions and by Nazis to kill 865,000 Jews at the Auschwitz concentration camp alone.

Death penalty experts say the United States turned away from the gas chamber and switched to lethal injections due to the horrific nature of the lethal gas deaths. They said gas chamber executions were slow deaths in which prisoners gasped for breath, thrashed their restrained bodies and appeared to be in excruciating pain.

Arizona, California, Missouri and Wyoming are the only states with decades-old lethal-gas execution laws still on the books. Arizona is the only one that still has a working gas chamber.

Atwood is scheduled to be executed with an injection of pentobarbital on June 8 for his murder conviction in the killing of 8-year-old Vicki Hoskinson in 1984.

Authorities have said Atwood kidnapped the girl, whose remains were discovered in the desert northwest of Tucson nearly seven months after her disappearance. Experts could not determine the cause of death from the bones that were found, according to court records.

Atwood’s defense team didn’t have immediate comment on the method of execution for their client.

Deborah Denno, a Fordham Law School professor who has studied executions for more than 25 years, said a substantial number of condemned people don’t make a selection when asked how they want to be put to death.

“No one knows the reasons (why), but one factor is they are depressed and have given up,” Denno said. “This is the least of their worries. They are going to die.”

The state’s nearly eight-year hiatus in executions that ended with Dixon’s May 11 death has been attributed to the difficulty of securing lethal injection drugs as manufacturers refuse to supply them and problems encountered during the July 2014 execution of Joseph Wood.

Wood was given 15 doses of a two-drug combination over nearly two hours. Wood snorted repeatedly and gasped before he died. His attorney said the execution had been botched.

In recent years, Oklahoma, Mississippi and Alabama have passed laws allowing executions with nitrogen gas, at least in some circumstances, though experts say it’s never been done and no state has established a protocol that would allow it, according to the Death Penalty Information Center.

The last prisoner to be executed in a U.S. gas chamber was Walter LaGrand, the second of two German brothers sentenced to death for killing a bank manager in 1982 in southern Arizona. It took LaGrand 18 minutes to die in 1999.

Both brothers chose the gas chamber in hopes that courts would find the method unconstitutional. While Karl LaGrand accepted the state’s last-minute offer of lethal injection, Walter LaGrand rejected it, saying he would prefer a more painful execution to protest the death penalty.

The case drew widespread criticism in Germany, which has no death penalty, and prompted repeated diplomatic protests.

Arizona’s gas chamber refurbishment was condemned internationally, including coverage in Israel and Germany drawing parallels to Holocaust atrocities.

In early April, a judge denied a request by the Jewish Community Relations Council of Greater Phoenix to bar the state from using cyanide gas to carry out executions in Arizona.

Arizona now has 112 prisoners left on the state’s death row.