Three former California governors on Thursday threw their political weight behind a proposed ballot measure to dramatically speed up the state's notoriously slow death penalty system, increasing the likelihood voters will be asked next fall to reform an appeals process for death-row inmates that many experts consider beyond repair.

George Deukmejian, Pete Wilson and Gray Davis backed the death penalty measure, which in theory would require the California court system to finish death penalty appeals in about five years -- a profound shift for a state that typically takes 12 to 15 years to complete appeals for condemned killers who then move on to the federal courts, where cases languish for another decade or more before an execution can take place.

California has not executed any of its more than 740 condemned inmates since 2006 as a result of legal challenges to the state's lethal injection procedure, and there are unlikely to be any scheduled for the next few years barring resolution of that issue. Current Chief Justice Tani Cantil-Sakauye and former Chief Justice Ronald George have branded the state's system "dysfunctional."

The ballot measure would come as other states are either abandoning the death penalty -- Washington's governor suspended it this week -- or struggling to find lethal injection methods that hold up in court. California voters in 2012 defeated a ballot measure that would have abolished the death penalty and replaced it with life in prison without parole.

Death penalty opponents plan to campaign against the measure, and challenge it in court if voters approve it, arguing that it strips key legal rights from death row inmates.

The measure's supporters must gather about 800,000 signatures, validated by June 26, to qualify for the ballot.

"This initiative will bring common sense reform to a broken system," Davis said at a Los Angeles news conference.

Gov. Jerry Brown and Attorney General Kamala Harris have not taken a position on the measure, their spokesmen said Thursday.

Under the proposed reforms, death penalty appeals would for the most part be reviewed by the state courts of appeal, with the California Supreme Court a last resort. The measure calls for other reforms, including overhauling the way death row inmates' lawyers are appointed, which can take several years before the first appeal is filed.

The reforms would avoid some of the state's problems adopting a lethal injection method by allowing prison officials to change the execution procedure without going through complex administrative review rules.

Courts have twice ordered the state to scrap its method because prison officials failed to comply with those rules.

But whenever California opts for a new execution method, it must still be reviewed by a federal judge handling a long court battle over the legality of San Quentin's lethal injection protocol.

As it stands, death row inmates have an automatic right to appeal to the state Supreme Court, and then can file petitions for habeas corpus based on new evidence turned up during appeals. In the case of condemned Santa Clara County killer Miguel Bacigalupo, that process took about 25 years before he was recently spared the death penalty because of prosecutor misconduct at his original trial.

The ballot measure also could not address appeals in the federal courts, which typically take at least a decade from the lower courts to the U.S. Supreme Court.

But Kent Scheidegger, legal director of the pro-death penalty Criminal Justice Legal Foundation and a key drafter of the measure, said there is no reason California cannot carry out executions less than 10 years after a jury hands down a death sentence.

"We've had this notion that capital cases are these hugely different things and it's not true," he said. "Judges can move these things along if they want to."

The measure includes other provisions, including requiring death-row inmates to work in prison and moving them into the general prison population instead of on a death row.

Death penalty foes say the measure will just lead to more expensive legal battles, delays and heighten the threat en of executing an innocent inmate.

"California has to abide by constitutional minimums," said Ellen Kreitzberg, a Santa Clara University law professor. "They are misleading the public with false promises."

Howard Mintz covers legal affairs.

Death penalty in California
last execution in California
Number of inmates currently on death row
Number of years it takes to complete the state appeals process before moving on to the federal court system