San Francisco ? A federal appeals court threw out more than 100 death sentences in Arizona, Montana and Idaho on Tuesday because the inmates were sent to death row by judges instead of juries.

The case stems from a 2002 decision by the U.S. Supreme Court, in which the high court found that juries, not judges, must render death sentences. But the Supreme Court left unclear whether the new rules should apply retroactively to inmates awaiting execution.

In an 8-3 vote, the San Francisco-based 9th U.S. Circuit Court of Appeals said all condemned inmates sentenced by a judge should have their sentences commuted to life in prison.

The ruling applies only to Arizona, Idaho and Montana, the only states in the 9th Circuit that have allowed judges to impose death sentences.

Two other states, Nebraska and Colorado, also have allowed judges to sentence inmates to death. But the federal appeals courts that oversee them have yet to rule on the issue.

The ruling affects approximately 3 percent of the 3,700 people on death row in the United States.

“By deciding that judges are not constitutionally permitted to decide whether defendants are eligible for the death penalty, the Supreme Court altered the fundamental bedrock principles applicable to capital murder trials,” Circuit Judge Sidney Thomas wrote for the court.

Defense attorneys hailed the verdict.

“This is fundamental justice,” said Ken Murray, a federal public defender in Phoenix.

Murray and attorneys for Arizona estimated that the decision affected around 100 inmates on that state’s death row alone.

Arizona Atty. Gen. Terry Goddard said his state would ask the U.S. Supreme Court to review the decision. Even if the ruling is upheld, he said Arizona could conduct new “mini-trials” with juries deciding whether to impose life or death sentences in individual cases.

In Idaho, the ruling is expected to reduce the death sentences of at least 15 condemned inmates, while Montana Atty. Gen. Mike McGrath said the ruling should have no effect on that state’s five death-row inmates.

McGrath said the specific circumstances of those cases insulated them from the appeals court decision.

Scott Crichton, executive director for Montana’s chapter of the American Civil Liberties Union, said the ruling “takes us a step closer to the day when the United States will join the civilized nations of the world in outlawing the cruel, inhumane and biased application of the death penalty.”

The case the appeals court used to decide the issue concerned Arizona inmate Warren Summerlin, who was found guilty of murder in the 1981 slaying of Brenna Bailey, 36.