Van Houten went before a California parole board for the 17th time today, backed by supporters who said she no longer deserves to be behind bars.
The parole board denied the request.
Van Houten was one of five people, including Manson, sentenced to death for her participation in a drug-fueled murder spree ordered by Charles Manson in 1969 at the height of California's "Summer of Love." The sentences were later commuted to life in prison.
"Leslie, my God, is unbelievable," her father, Paul Van Houten, said. "I'll guarantee you there are people on the outside who haven't done as well."
Van Houten, 60, has been described by her supporters and prison staff as a model inmate. She is working as a college tutor while studying for her master's degree in humanities and has not had one prison infraction on her record in more than 40 years.
But Debra Tate, whose pregnant sister, Sharon Tate, was one of seven people slain by the so-called Manson family during two nights in August 1969, said she had collected 60 letters asking the parole board to keep Van Houten behind bars.
Tate, who has made a full-time job of advocating to keep Manson and his followers in prison, said she has no doubt that Van Houten has been a model prisoner, but pointed out that she thrived only in a tightly controlled environment.
"Is a tiger dangerous if it gets out of its cage? We proved that at the L.A. zoo," Tate said. "In the cage they are fine. You cannot let them out."
Tate said she still gets regular death threats from Manson supporters, at a rate of about three to four a year.
Since the parole board today denied what is called a "parole grant" for Van Houten, the Board of Parole now has 120 days to conduct a decision review. Once that is complete, her case will go to the governor for review.
California Gov. Arnold Schwarzenegger recently struck down a parole recommendation for another one-time Manson follower, Bruce Davis, who is serving life sentences for two murders unconnected to the Tate killings.
Van Houten's reputation as a prisoner dedicated to education and volunteerism is in stark contrast to the brutal savagery that made her and the rest of Manson's eager killers household names four decades ago.
In 1969, Van Houten had been upset that she was not picked to come along when Susan Atkins, Patricia Krenwinkel and Charles "Tex" Watson broke into Sharon Tate's posh Los Angeles-area home and butchered the eight-months pregnant actress along with four visitors at the house that night; celebrity hair stylist Jay Sebring, coffee heiress Abigail Folger, writer Wojciech Frykowski and teenager Steven Parent, who had been visiting a friend on the property.
Van Houten, then 19, joined Watson and Krenwinkel the next night when they savagely killed supermarket owner Leno LaBianca and his wife, Rosemary. Van Houten would later say Rosemary LaBianca was already dead when she stabbed her in the back more than a dozen times. Before leaving, she raided the couple's fridge for cheese and milk and changed into Rosemary LaBianca's clothes.