When Jerry Brown was governor from 1975 to 1983, he pardoned 404 convicted criminals, removing the convictions from their records, and granted one commutation, shortening a prisoner’s sentence.

But during his past eight years in office, he has granted 1,189 pardons and 152 commutations, far more than any other governor in modern California history.

“The atmosphere, the gangs, the hopelessness, sentences that are so long ... the no-exit attitude has made it virtually impossible to have any strong rehabilitative atmosphere,” Brown said in an interview. “This has given me the interest, where I can, in instilling hope.”

When asked what has changed, Brown pointed to another set of numbers: California had 12 prisons and about 25,000 inmates in 1975. By 2011, thanks to tough-on-crime changes that imposed fixed-term sentences, mandatory prison time for certain crimes, and long increases for repeat offenders, the state had 173,000 inmates in 35 California prisons and some private lockups in other states, a population since reduced to 128,000 by federal court orders and new laws.

Along the way, Brown said, California prisons became places of punishment and despair, with dwindling prospects of turning lives around to prepare inmates for release to the free world.

Clemency isn’t the only way the governor has tried to change that atmosphere.

Brown backed laws to move up parole hearings for youthful offenders and elderly prisoners. He also sponsored Proposition 57, the 2016 initiative that allowed the state parole board to consider releasing inmates after their term for the crime that sent them to prison, without waiting until they had served additional years for previous crimes. The new laws left the final decision to the parole commissioners, appointed by the governor to decide whether an inmate can be safely released.

Most of Brown’s pardons have erased long-ago convictions for drug crimes and nonviolent offenses. Pardons allow individuals to obtain many types of state licenses unavailable to convicted felons, and, for those whose crimes did not involve weapons, to possess firearms. For noncitizens who are legal U.S. residents, a pardon also spares them from deportation.

Similarly, while some of Brown’s sentence commutations set prisoners free, more often they have made inmates serving life-without-parole terms eligible for parole, or moved up an inmate’s previous parole eligibility date, allowing the parole board to weigh issues of rehabilitation and public safety. So far, he has not sought to commute the death sentences of any of the state’s 739 condemned prisoners.

“It’s not a get-out-of-jail-free card,” said Heidi Rummel, a University of Southern California law professor who works with inmates and supervises students who represent them in parole proceedings. “The fact that the governor is willing to look at how people do in prison has created a lot of momentum for positive rehabilitation. ... There are long waiting lists for rehab programs where there never were before.”

It’s also increased the number of prisoners and ex-convicts applying for clemency, far more than Brown said he could consider But he has set up a review process in which his staff screens the application, then studies the applicant’s record both in and out of prison and meets with prison staff and others who know the inmates or ex-convicts before recommending a commutation or pardon.

The final decision is up to the governor, unless the prisoner or former inmate has two or more felony convictions. The state Constitution then requires a majority of the California Supreme Court to approve a grant of clemency. The court, apparently anticipating a wave of applications in Brown’s final months in office, adopted a new policy in March that said it would not second-guess a governor’s decisions, but would reject them only if they represented an “abuse of power.”

In recent weeks the court, without stating reasons, has rejected one of Brown’s proposed pardons and two commutations.

When Brown first took office, virtually all felony crimes carried a range of sentences — one to 10 years, for example — and the parole board determined release dates. The system drew criticism from across the political spectrum, with conservatives claiming undue leniency and liberals alleging discrimination against minorities. Those “indeterminate sentences” were discarded in 1977 when Brown signed a law setting fixed terms — like two, four or six years — for most felonies, with the sentencing judge making the decision.

He wouldn’t sign that 1977 law today, Brown said.

“I didn’t fully understand the implications of where it would lead,” with substantial increases in the legally mandated sentences, particularly for gun crimes and repeat offenders, he said. “I thought about the idea of making things clear, certain and fair” with sentences defined for each crime. “I never thought that when you tell a man that you know when he’s getting out, he loses the incentive to transform his life.”

The 1977 law left the parole board with the sole task of deciding when to release inmates serving terms of up to life in prison, including convicted murderers, and, later, “three-strikers” serving 25 years to life for a third felony under a 1994 ballot measure. The laws also allowed the governor to veto a parole board’s decision to release an inmate, authority that was often used by previous governors but seldom by Brown.

“I believe in wide discretion for the parole board,” Brown said in the interview. “I believe in pardons, and I believe in commutations.”

Kate Chatfield, a University of San Francisco Law School professor and policy director of Re:store Justice, which advocates for less severe prison sentences, represented an inmate who spent about 20 years in prison for shooting and wounding a robbery victim before Brown commuted his sentence and freed him in August. She has another application pending.

Most of those who have won commutations are “poor, people of color, without attorneys,” Chatfield said. She compared Brown’s pardons and commutations to “Pope Francis washing the feet of migrants. ... It hasn’t made a dent in mass incarceration but it is wonderfully symbolic. It speaks to a belief in rehabilitation, in people being more than the worst of their actions.”

Brown, a former Jesuit seminarian, also sounded a spiritual theme.

“From my background, I do believe that redemption is an essential element of being human,” he said.

“Many people in today’s society do not believe in either forgiveness or redemption,” Brown added. “They believe that what you do is who you are. That philosophy is not something that I share. I don’t think it’s Christian ... and it does not comport with historical notions of justice.”

Bob Egelko is a San Francisco Chronicle staff writer. Email: begelko@sfchronicle.com Twitter: @BobEgelko