The youngest member of the Manson cult has been approved for parole, 48 years after the notorious group carried out its killing spree.

A California state panel determined that Leslie Van Houten, who is now 68, had drastically changed her life and was no longer a threat to society.

But Van Houten – who has served more than four decades of a life sentence for her part in a double murder – may still be blocked from leaving jail.

The final decision on Ms Van Houten's release rests with state governor Jerry Brown, who last year rejected her parole.

In stopping her release then, Mr Brown said Van Houten had failed to adequately explain how a model teenager and former homecoming princess from a privileged Southern California family could have transformed into a merciless killer by the age of 19.

“I've had a lot of therapy trying to answer that question myself,” Ms Houten told the parole panel on Wednesday.

“To tell you the truth, the older I get the harder it is to deal with all of this, to know what I did, how it happened."

Ms Van Houten's attorney, Rich Pfeiffer, said he believed his client had answered the governor's question and he should agree to her release.

“My hope is he's going to follow the law and let his commissioners do their job,” he said.

He added: “I'm getting her out of here. That's not an issue. The question is when."

No one who took part in the Manson clan's two-night killing rampage has been released from prison so far.

Van Houten told the panellists she was devastated when her parents divorced when she was 14. Soon after, she said, she began socialising with an outcast crowd in the Los Angeles suburb of Monrovia.

She started smoking marijuana and then began taking LSD at 15. When she was 17, she and her boyfriend ran away to San Francisco's Haight-Ashbury District during San Francisco's summer of love.

When they returned, she said, she discovered she was pregnant. When her mother found out, she ordered her to have an abortion.

Soon after, while travelling up and down the California coast, she met Manson, who was living on an old abandoned movie ranch on the outskirts of Los Angeles.

He had recruited what he called a “family” to survive a race war he would launch by committing a series of random, horrifying murders. His disaffected youthful followers became convinced that the small-time criminal and con man was actually a Christ-like figure and believed him.

Van Houten went on to describe how she joined several other members of the “Manson Family” in killing Los Angeles grocer Leno La Bianca and his wife, Rosemary, in their home on 9 August 1969.

She was not with Manson followers the night before when they killed pregnant actress Sharon Tate and four others during a bloody rampage.

On the night of the second attack she said she held Rosemary La Bianca down with a pillowcase over her head as others stabbed her dozens of times. Then, ordered by Manson disciple Tex Watson to “do something,” she picked up a butcher knife and stabbed the woman more than a dozen times.

“I feel absolutely horrible about it, and I have spent most of my life trying to find ways to live with it,” she added quietly.

“No member of the Manson family deserves parole, ever,” the La Biancas' nephew Louis Smaldino said. “She is a total narcissist and only thinks of herself and not the damage she has done.”

The voice of the La Biancas' oldest grandson, Tony LaMontagne, broke as he noted he's about to turn 44, the same age his grandfather was when he was killed.

“Please see to it that this fight doesn't have to happen every year for the rest of our lives,” he said of Van Houten's nearly two dozen parole hearings.

Family members left before the panel announced its decision.

In reaching it, Parole Commissioner Brian Roberts and Deputy Commissioner Dale Pomantz said they took into account Van Houten's entire time of incarceration. During those years she has earned bachelor's and master's degrees in counselling, been certified as a counslelor and headed numerous programmes to help inmates.

“You've been a facilitator, you've been a tutor and you've been giving back for quite a number of years,” Mr Roberts said.

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Yet he warned her that living in society again would not be easy. He noted parole officials have heard from “tens of thousands” of people who don't want her released.

Others, he added, including many who have known her since childhood, spoke up for her, saying they've seen her mature in prison and become a different person.