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.

Affects three states

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, have also 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 R. Thomas wrote for the court.

Defense attorneys hailed the verdict.

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

Murray estimated that the decision affects at least 100 inmates on Arizona's death row alone.

If the decision stands, Arizona and the other states might hold new penalty trials, convening juries to decide between life and death, said John Pressley Todd, a lawyer with the Arizona Attorney General's office.

He said the state was trying to determine exactly how many condemned inmates are affected by the ruling.

"We are disappointed. We are going to appeal," said Kent Cattani, chief counsel for the Arizona Attorney General's office.

The ruling is expected to reduce the death sentences of at least 16 condemned inmates in Idaho. Montana Assistant Attorney General Pamela Collins said state attorneys were reviewing the decision to determine whether its five condemned inmates would be affected.

"This may cause some chaos in the short term. I don't think this is going to hold up," Collins said.

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.

The Tempe finance company administrator's body was found in the trunk of her car a day after she visited Summerlin to check on money he owed. Summerlin was convicted in 1982 and a judge sentenced him to death.

Prior to the U.S. Supreme Court's ruling last year, a jury determined guilt or innocence, but one or more judges evaluated whether the particulars of the case made it worthy of the death penalty in Arizona, Idaho, Montana, Colorado and Nebraska.

The Death Penalty Information Center, which compiles statistics on capital punishment, calculated that since 1976, those five states have executed 29 people under laws allowing nonjury sentencing.

In July, meanwhile, the 11th U.S. Circuit Court of Appeals ruled in a Florida case that the Supreme Court decision should not be applied retroactively in some death penalty cases. In Florida, Alabama, Indiana and Delaware, juries recommend a life or death sentence but judges are allowed to give the death penalty against the jury's wishes.