VACAVILLE, Calif. - During the 26 years that James Alexander has spent in prison for killing a fellow drug dealer, he has maintained a spotless behavior record and devoted himself to helping other inmates shake addictions.

He has been such a model prisoner that state parole commissioners, on three occasions, recommended his release. All three times, California Gov. Arnold Schwarzenegger overruled them.

Alexander, 47, is among the hundreds of "lifers" whom state parole boards have deemed rehabilitated and ready to rejoin society, but who sit behind bars because their crime was murder.

In recent years, some judges have sided with lifers, ruling that the state cannot deny an inmate parole solely because of the gravity of his or her original offense, but must provide "some evidence" that the prisoner poses a threat to public safety if released.

The legal notion that corrections officials must, in essence, show that an inmate remains a threat to society is being challenged in a pending case before the U.S. Court of Appeals for the Ninth Circuit.

In California, 23,000 state prisoners are serving life sentences who are technically eligible for parole. Nearly 4,000 other inmates serving "life without parole" sentences, and 685 on death row can never be considered for release.

Until the 1980s, when a succession of tough-on-crime governors came to power, parole was routine for those sentenced to life who showed evidence of rehabilitation.

In 1983, California Gov. George Deukmejian invoked what was then a rarely used 1913 law to overrule the parole board decision to free murderer William Archie Fain after an outcry from the small town of Oakdale, where Fain's victims had lived.

His successor, Pete Wilson, reversed parole grants more frequently, and Gov. Gray Davis embraced a virtual no-parole-for-murderers policy, freeing only six during his time, five of them women whose crimes stemmed from domestic abuse.

Schwarzenegger also has been loath to release killers, granting only four such paroles himself, but allowing more than 300 other parole board decisions to go through without his review.

There is political risk also in granting paroles, as former Arkansas Gov. Mike Huckabee discovered recently when a man he paroled a number of years ago killed several police officers in Washington state. A potential presidential candidate, Huckabee has faced uncomfortable questions.

Despite a federal court order to reduce the state's prison overcrowding, neither Schwarzenegger nor corrections officials have suggested considering violent offenders for early release.

Victims-rights organizations defend what they consider the governor's responsibility, as well as power, to keep murderers off the streets, especially in the current economic crisis, which has cut funding for law enforcement and parole supervision.

"For the sake of public safety - that's what we have life sentences for," said Harriet Salarno, head of Crime Victims United of California whose 18-year-old daughter, Catina, was killed by a man who comes up for a ninth parole hearing next year.

Bill Schmidt, a lawyer who specializes in representing lifers, says whether reformed prisoners should get parole is often clouded by the horrific nature of their crime.

For example, some of Charles Manson's accomplices in the 1969 cult slayings have unblemished records for four decades. Nonetheless, he said, they routinely have been denied parole.

While popular opinion may back keeping killers locked up forever, "where does the law give the subjective authority for the governor or the board to say, 'No, your crime was so horrendous that we're not ever going to let you out'?" Schmidt asks.

In the case now before the Ninth Circuit, convicted murderer Ronald Hayward challenged Davis' reversal of the parole board's decision to release him after 27 years' imprisonment for the stabbing death of a motorcycle gang member who had tried to rape Hayward's girlfriend.

A three-judge panel of the appeals court ruled in January 2008 that Hayward's constitutional right to due process was violated because the governor failed to cite any evidence he was still dangerous.

The three-judge panel's decision was suspended four months later by the court's vote to reconsider the case with a full 11-judge panel.

Supervising Deputy Attorney General Jennifer Neill has urged the court to reconsider whether prisoners have a liberty interest in parole decisions. Life prisoners have no right to a term less than life, Neill argues, so denial of parole "merely means that the inmate will have to serve out his sentence as expected."

Some legal scholars say the decision in Hayward's case will depend on how the federal judges interpret the intent of laws on sentencing.

"It goes back to the question of whether we want sentences to be punitive and how to weigh rehabilitation vs. punishment," said Pepperdine University law professor Laurie Serafino.

As for the Hayward case's implications for him, Alexander has no illusions.

"It's hard for me to have faith in the integrity of the system," he said, "when the state agency charged with finding me suitable for parole has done so on numerous occasions and I'm still here."