Cyntoia Brown, jailed as a 16-year-old for murdering her alleged rapist and whose case was championed by US celebrities as a symbol of unfair prison sentencing, has been released from the Tennessee Prison for Women, ABC reports.
Kim Kardashian West, Rihanna, Snoop Dogg and LeBron James and several other US-based celebrities had lobbied for Ms Brown's release, calling her a sex trafficking victim.
She was granted clemency in January by outgoing governor Bill Haslam, commuting a life sentence for murdering 43-year-old Nashville real estate agent Johnny Allen, whom she accused of rape.
Police said she shot Allen in the back of the head at close range with a gun she brought to rob him after he picked her up at a drive-in restaurant in Nashville to have sex with her.
At the time of the incident, Brown had run away from her adoptive family in Nashville in 2004 and began living in a hotel with a man known as "Cut Throat".
She alleged that he forced her into prostitution and verbally, physically and sexually assaulted her, according to court documents.
Her lawyers contended she was a victim of sex trafficking who not only feared for her life but also lacked the mental capacity to be culpable in the slaying because she was impaired by her mother's alcohol use while she was in the womb.
At the time of her conviction, the state of Tennessee argued successfully in lower courts that Brown's sentence was not in violation of a federal prohibition on sentencing juveniles to life in prison.
The state argued then that she was not sentenced to life as she was eligible for parole after serving at least 51 years, which would have been in 2059.
Now 31, Brown will remain on parole for 10 years, on condition that she does not violate any state or federal laws, holds a job and participates in regular counselling sessions, Haslam's commutation says.