Patricia Krenwinkel, one of the last surviving followers of cult leader Charles Manson, remains in prison.
California Gov. Gavin Newsom over the weekend disagreed with the parole board's recommendation to grant the 74-year-old's 15th parole request.
Newsom said Krenwinkel continues to pose a threat to the public because of her commitment to Manson's "racist and apocalyptic ideology."
As a member of the so-called Manson Family, Krenwinkel was involved in a series of murders in Los Angeles in the summer of 1969 in which the heavily pregnant wife of filmmaker Roman Polanski, Sharon Tate, the entrepreneurial couple Leno and Rosemary LaBianca and four other people died in agony.
She later admitted to stabbing Leno LaBianca in the stomach with a fork, smearing the victim's blood on the walls and inciting a race war.
Krenwinkel had been sentenced to death for murder in the spring of 1971.
After all death sentences were overturned in California, her sentence was commuted to life imprisonment in 1972.
Manson died of complications from cancer in November 2017 after decades behind bars.