California Governor Jerry Brown said Van Houten (pictured above) - serving a life sentence for killing a grocer and his wife over 40 years ago - had failed to explain how she had turned from a mild-mannered teenager into a killer.

"Both her role in these extraordinarily brutal crimes and her inability to explain her willing participation in such horrific violence cannot be overlooked and lead me to believe she remains an unacceptable risk to society if released," Brown wrote.

Van Houten has now been denied parole 20 times.

Van Houten participated in the August 1969 killings of Leno and Rosemary La Bianca, a day after other Manson family members murdered actress Sharon Tate, the pregnant wife of filmmaker Roman Polanski, and four others. Van Houten did not take part in the Tate killings.

Van Houten told her parole hearing how she had helped tie a pillowcase over the head of Rosemary La Bianca with a lamp cord and hold her down while another member of the Manson family stabbed the woman. The word "WAR" was carved on the stomach of her husband, Leno La Bianca.

"I don't let myself off the hook. I don't find parts in any of this that makes me feel the slightest bit good about myself," she told the panel.

The parole board ruled that Van Houten was no longer the violent young woman who committed the gruesome murder, citing the facts that she had completed college degrees and been a model inmate.

"Gov. Brown has done a good thing here, and I think he sees what we see - that this was an unrepentant killer," said Lou Smaldino, nephew of the La Biancas.

Van Houten's lawyer, Rich Pfeiffer, said he expected Brown's decision because of the political pressure put upon him. He said he will challenge the decision in Los Angeles County Superior Court. Van Houten's next parole hearing could come in as little as a year, he added.

Manson (pictured at right), 81, and other followers involved in the killings are still serving life sentences. Patricia Krenwinkel and Charles "Tex" Watson have each been denied parole multiple times, while Susan Atkins died in prison in 2009.

jbh/cmk (AP, Reuters)