John Burgess pleaded guilty to involuntary manslaughter in the death of Donna Jou in 2009.
Burgess, a registered three-time sex offender, met Jou in 2007 on Craigslist, where she advertised as a math tutor.
Burgess said he and Jou went to his house one night to party. He confessed to giving her alcohol, marijuana, cocaine and heroin. He said he found her dead of an overdose the next morning. He denied killing her, but the case remains clouded in mystery.
Jou's body was never found, though many searches have been conducted.
In a stunning courtroom admission in 2009, Burgess said he had panicked after finding Jou dead and cast her body into the ocean.
Burgess was released from prison back in April after serving two years of a five-year prison term. He was sent to Men's Central Jail in Los Angeles to serve time for a misdemeanor.
Jou's parents, however, do not believe Burgess' account of what happened to their daughter. Wednesday, they rallied with supporters, saying that Burgess is withholding the truth.
"No one has a reason to conceal a dead body unless he's trying to hide something. Not an accidental death. We never buy it. No one with a right frame of mind accept a story from a multiple-time convicted sex offender," said Jou's father, Reza Jou.
They want the case reopened, but the district attorney said they will not do that because there is no evidence to justify doing so.
"A 35-year-old man took my daughter to his house, drugged her, gave her alcohol and caused her death. This is murder," said Jou's mother, Nili Jou.
"We're giving them incentive to put everyone through this kind of torture by telling them, 'If by chance you can get away with it, you're almost scot-free,'" said Lisa Jou, Donna's sister.