(CNN) Leslie Van Houten, a Charles Manson follower convicted in a 1969 killing spree, was denied parole for the third time in three years Monday.

Leslie Van Houten

The California parole board in January recommended parole for Van Houten. California Gov. Gavin Newsom said in a parole release review that despite Van Houten's productive time in prison -- she earned a bachelor's and master's degrees and completed "extensive" self-help programming -- the negative factors of her involvement in the murders outweighed the positive factors.

"Ms. Van Houten and the Manson family committed some of the most notorious and brutal killings in California history," Newsom said. "When considered as a whole, I find the evidence shows that she currently poses an unreasonable danger to society if released from prison at this time."

Van Houten, 69, was 19 years old when she met Charles Manson and became part of his murderous cult that came to be called the "Manson Family," according to parole documents.

On August 10, 1969, she and other members of the Manson Family brutally stabbed Leno and Rosemary LaBianca to death at their home in Los Angeles. Van Houten was arrested November 25, 1969.