(CNN) Cyntoia Brown has been incarcerated for nearly half her young life. She is serving a life sentence in Tennessee for killing a 43-year-old man who had bought her for sex when she was 16 years old.

Now 30, Brown's fate may be determined by Tennessee Gov. Bill Haslam, who can choose to grant Brown clemency before his term ends on January 19.

A US congressman, several Tennessee lawmakers and a number of A-List celebrities including comedian Amy Schumer and actress Ashley Judd are joining growing calls for Brown's clemency -- calls which have prompted viral hashtags like #FreeCyntoiaBrown and #Clemency4Cyntoia as well as online petitions, some of which have received several hundred thousand signatures.

I encourage and plead with my Tennessee Governor @BillHaslam to grant #Clemency4Cyntoia . Cyntoia Brown was a victim of child sex trafficking, raped and forced into paid sexual exploitation to stay alive. She deserves our empathy and your mercy.

Years-old case ignites new interest

In 2004, Brown killed Johnny Mitchell Allen who she says had solicited her for sex and taken the 16-year-old back to his house. Prosecutors at the time said Brown shot Allen in the head while he was sleeping, stole money and guns, took his truck, and fled the scene. They argued the killing wasn't motivated by self-defense, but robbery. Brown said she was scared for her life by Allen's behavior, and took money for fear of returning empty-handed to her pimp, nicknamed "Cut Throat."

A juvenile court found Brown competent to be tried as an adult. She was convicted of murder and robbery, and sentenced to life in prison.

Cyntoia Brown in 2010, at the Tennessee Prison for Women.

Though more than a decade since her trial, the harsh punishment for a teenage victim of sex trafficking sparked outrage around the US -- particularly after celebrities Rihanna and Kim Kardashian West came to her defense on social media in 2017.

Since Brown's conviction, juvenile sentencing guidelines in Tennessee have been amended: "If Cyntoia Brown were tried today, legal experts say she would not have been tried in the same way," explains Stacy Case, an anchor on WZTV, in Nashville, who had been investigating reports of sex trafficking in Tennessee when she came across Brown's story. "Our courts today would view her as a child sex slave... she would be viewed as a victim."

In fact, it was Brown's trial that inspired a documentary that eventually helped to alter the way Tennessee deals with sex trafficking victims, particularly those who are juveniles.

"If you look at Cyntoia's original transcripts, they are peppered with the phrase 'teen prostitute,'" says Derri Smith, founder and CEO of non-profit End Slavery Tennessee. "Well we know today there's no such thing as a teen prostitute ... because this teen may think that she decided this was her idea to be raped multiple times a day and give money to someone else, it's pretty clear there's an adult behind that who's manipulating and exploiting her."

Abandoned, abused and exploited

In the 2011 documentary "Me Facing Life: Cyntoia's Story," Brown describes being forced into prostitution at a young age, sex trafficked, and raped repeatedly.

"The first time he did something to me is when he choked me and I passed out," Brown recounts of her alleged pimp "Cut Throat" in the documentary. "I made him money...he wasn't going to let me go nowhere. He told me he'd kill me."

Cyntoia Brown as a child.

The documentary by Daniel H. Birman Productions, Inc . also revealed new evidence that suggests Brown suffered from Fetal Alcohol Syndrome, which can cause brain damage -- evidence that the jury which convicted her in 2004 never saw. Her mother also admitted to drinking heavily while pregnant, according to court records from a 2014 appeal.

"Then as a teenager, she did have a nice adoptive family," says Case, "but because of her experiences she veered and ended up on the wrong side of law -- and ended up being sex trafficked. If she had grown up differently, if she had had other opportunities, it may not have ended up that way."

A second installment of the documentary is scheduled for release in 2019.

Fighting for a second chance

Since her sentencing, Brown has spent all of her adulthood in prison -- but her advocates say she has worked to transform herself during her time behind bars.

"She is light years today, as a woman, different from the traumatized 16-year-old that she was," says Smith. "She's mentoring... troubled youth, working on her college degree, she is planning a nonprofit so she can help other young people."

Cyntoia Brown at her graduation.

Brown received her associates degree from Lipscomb University in 2015, and according to Smith is working towards her Bachelor's degree from inside prison. She's also collaborating with Tennessee's Juvenile Justice System to help counsel young people at risk, and her supporters say she's been a model inmate during her incarceration.

"I learned that my life was -- and is -- not over," Brown says over the phone in a clip titled "Prison Reflections" from the documentary filmmakers... "I can create opportunities where I can actually help people."

Cyntoia Brown in the back of a van, during her criminal trial in 2006.

Juveniles serving life sentences

Although her story has captured national attention, Brown is among more than 11,000 people currently serving life sentences or "virtual life sentences" for crimes committed before they were 18, according to the non-profit research and advocacy group The Sentencing Project

According to Human Rights Watch , the United States has one of the highest rates of juvenile detention in the world, and until a Supreme Court ruling six years ago, it was one of the only countries in the world to allow juveniles to be sentenced to life in prison without the possibility of parole.

That 2012 Supreme Court decision, which banned life without parole for juveniles who commit murder, gave momentary hope to Brown's case -- but her sentence does carry the possibility for parole. Despite attempts at an appeal, the Tennessee Supreme Court recently affirmed her sentence was constitutional; Brown will not be eligible for parole until she's 67 years old. The unanimous decision renewed interest -- and outrage -- around her case.

"I cannot find a case where there has been such a harsh punishment imposed on a similarly aged person who was, after all, in the process of being raped as a child when this crime happened," Wendy Murphy, former sex crimes prosecutor and sex violence law professor at New England Law Boston told CNN. "We can't take that out of this equation."

But as CNN legal analyst Joey Jackson explains, sentences for crimes as heinous as murder are not determined lightly: "The basic facts are, no one can take a life. So if you take a life, and it's not deemed to be self-defense, then it becomes problematic no matter what age you are -- and that's the issue."

Tennessee's Attorney General, which represented the state at Brown's appeal, declined to comment to CNN about her case.

Decision rests with governor

Gov. Bill Haslam on April 4, 2018, in Memphis, Tennessee.

Gov. Haslam declined an interview with CNN, but a statement from his office says he is "reviewing numerous clemency applications, including Cyntoia Brown's...there is no 'set' timeline, other than that any clemency grants would have to be completed by the time Governor Haslam leaves office on January 19. As of this point, Governor Haslam has granted clemency in 10 cases and other grants are forthcoming."

Brown's lawyers also declined to speak to CNN until the governor announces a decision. Gov. Haslam can choose to commute Brown's sentence to a lesser prison term, or allow her to be released for time served. He can also issue a pardon, or sidestep requests for her clemency altogether before he leaves office, which would punt the issue to incoming Republican Gov. Bill Lee. Typically, governors do not issue clemencies until the end of their terms.

"I know that the survivors that we serve are watching very carefully to see whether there is hope for them - because if they work really hard at their rehabilitation, like Cyntoia has, and society recognizes that and gives them a chance to move forward, that is exhilarating," says Smith of other sex trafficking victims she works with at End Slavery Tennessee. "But if instead they see that no matter how hard they work, their past is always going to define their future, that's disheartening."

Also joining the calls for her clemency are several Tennessee lawmakers, who gathered in Nashville for a press conference on the issue. Tennessee State Representative John Ray Clemmons pleaded for Brown's release: "In the interest of equity, in the interest of fairness, in the interest of justice, we as a state must address this issue, and set Miss Brown free."