Confusion and alleged "lies" still swirl around the strange case of an Indiana family that claimed a young girl they adopted was actually a full-grown woman who terrorized them, according to an upcoming documentary.

"There were arguments on both sides that she was an adult or she was a child," Beth Karas, a New York attorney and former prosecutor featured in the three-part Investigation Discovery documentary called "The Curious Case Of Natalia Grace," told Fox News Digital. 

"I’m leaning toward one side, but I don’t know that we’ll ever know everything," Karas said.

In April 2010, Michael Barnett and his then-wife, Kristine Barnett, adopted Natalia Grace, who has a rare form of dwarfism called spondyloepiphyseal dysplasia congenita and who they thought was a 6-year-old Ukrainian girl.

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Natalia Barnett

Natalia Barnett allegedly pretended to be a young girl at the time of her adoption. (Investigation Discovery)

Just roughly six months later, however, the parents allegedly began witnessing violent behavior and called into question whether Natalia was really a child or an adult woman who was scamming the family. The alleged behavior included hoarding knives in her room, urinating on her adoptive siblings, and even allegedly trying to kill her adoptive mom with Pledge cleaning solution, according to Michael Barnett. 

"She tried to poison and kill my wife," Michael said in the documentary, which Fox News Digital reviewed before its release. "One night, I opened my eyes and Natalia is standing at the foot of the bed with a knife in her hand."

Michael explained that they went through a few psychiatrists after Natalia began allegedly hoarding knives in her room, before one warned the family that they were in danger and diagnosed her as a sociopath. 

"She was doing as many things as possible to cause hurt or harm or mental distress to the entire family," he stated. "She would find little toy cars that the boys had, would take them and throw them into the street, so the boys would notice. She was baiting my kids to run into traffic so they’d get run over. I can’t put it into words … the everyday abject horror that we had to go through and live with." 

"There certainly was, like, a lot of fear, like, what if Natalia actually harms one of us," added Jacob, the oldest son.

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Barnett Family

Michael and Kristine Barnett, who adopted a young girl from Ukraine but soon questioned her real age after a series of alleged violent outbursts. (Investigation Discovery)

In the documentary, Karas pointed out that the ultimate question surrounding this entire case was whether Natalia was actually a child or an adult woman.

"On the adult side, there are people, neighbors, who observed her, lived next to her, observed her conduct and said she just wasn’t acting like a child," Karas told Fox News Digital. "There’s Michael saying that when they got her at what they thought was 6 years old, she had pubic hair and supposedly, you know, soon after she admitted to menstruating, that she was hiding it."

She went on to highlight that a family doctor didn't notice any bone growth in Natalia after a few years had passed. A mother of a girl who had the same disability and was the same age as Natalia, but looked more like a child with "chubby cheeks," also helped support the belief that Natalia was actually an adult.

"Natalia seemed older. Natalia acted out a little bit, sexually, toward people, other children and adults, so these things seem to support that she was an adult masquerading as a child," Karas said.

Natalia was taken to Larue Carter, an Indiana state mental hospital, to receive a mental health evaluation after she allegedly tried to push her adoptive mother, Kristine, into an electric fence on a farm that they visited for one of the boys' birthdays, according to Michael. Her stay there included health officials charging that she was "aggressive," "manipulative" and was even allegedly "propositioning men" at the hospital, according to the documentary.

After her release in 2012, due to alleged inconsistencies, the parents had her date of birth changed from 2003 to 1989 by an Indiana court, making the then-8-year-old a 22-year-old. 

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Larue Carter Hospital Indiana

Natalia was taken to Larue Carter, an Indiana state mental hospital. (Google Street View)

The parents decided to move her into an apartment in Westfield, Indiana, by herself, where she interacted with neighbors and led many of them to question who she was, how old she was and why her adoptive parents allowed her to live on her own.

Karas revealed to Fox News Digital that there’s "some pretty good evidence" Natalia was really a child because her biological mother in Ukraine said she was born in the early 2000s and a doctor who specialized in Natalia’s disease determined she was still growing after moving to the U.S.

Karas said that regardless of how old Natalia was, "She didn’t have the skills to live on her own and she was not put in an apartment that was modified for her disability."

In 2013, the family then planned to move to Canada with their biological children, where their oldest son was slated to start college. The Barnetts relocated Natalia from her apartment to another apartment complex in Lafayette, Indiana, which opened the door later to the eventual charges of neglect of a dependent that were brought against the adoptive parents in 2019, after their divorce, and led to their arrests after an investigation.

"If Natalia never entered our lives, I’d never get divorced," Michael claimed in the documentary.

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Beth Karas

Beth Karas, a New York attorney and former prosecutor, unveils questions and insight into the 2023 documentary "The Curious Case of Natalia Grace." (Patrick McMullan via Getty Images)

In 2022, the jury in the trial for Michael found that he was not guilty due to the judge not allowing Natalia’s age to be a factor in this case. In March 2023, Kristine had all eight counts of charges against her dropped after the prosecuting attorney argued that there was "insufficient evidence," according to Purdue The Exponent.

Karas explained that there are two sides to every coin when asked if the justice system had failed in any way following the Barnetts' charges getting dropped.

"It depends on whose side you’re talking to, right? If you’re talking to Michael, he’d say it operated exactly the way it should, and he walked away with an acquittal," the attorney said.

"He says he’s not guilty, but what the judge did was prevent the prosecution from introducing any evidence about Natalia’s age being an issue, and that’s what this whole story is about: Is she a child? Is she an adult?" she went on. "They had to dismiss half of their charges, they could not refer to age at all. The jury might have had a different verdict if they could have considered her age."

Karas said that the adoptive parents probably should have gone to the police, but it's rare to see children in custody. However, she added that the alleged acts like "homicidal thoughts, hoarding knives and standing at the foot of the bed with a knife in her hand in the middle of the night, that’s pretty scary stuff, so that could be something for the juvenile system, if necessary."

Karas also mentioned that because the two police departments had different investigations at different times, things may not have changed as much regarding the overall case. 

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"I don’t know if Detective Clouse had come into the picture earlier, if it would have really changed things," Karas said. "Maybe they would have gotten her some help. I mean, they were trying, they were getting her into a hospital, they were trying, you know? She was drawing pictures they said of things that, you know, scared them, like her thoughts – her homicidal thoughts."

"But if she was a child," Karas continued. "If she was abused as a child, maybe this is like her coping mechanism and she was fantasizing about wanting to hurt them because they were hurting her and she was pretty defenseless? I don’t know. Is she really evil? I don’t want to believe she is, but I really frankly don’t know where the truth is."