Was Natalia Grace really a child when she was adopted by an American couple, or was she a woman posing as a little girl?

Michael and Kristine Barnett adopted Natalia in 2010, in Florida, and he says they were told the girl was from Ukraine and had a rare form of dwarfism. Michael Barnett said the couple believed the girl was 6.

But both are now charged with felony neglect of a dependent and authorities say they abandoned her in Indiana while they moved to Canada in 2013. The couple, who are now divorced, claim they were scammed into adopting Natalia, who is really a 30-year-old woman, they say.

Trouble began not long after they adopted Natalia, he said. She had an advanced vocabulary for a child, he said, and there were signs that she had already begun menstruating.

According to Michael, Natalia twice tried to kill Kristine. Once, by trying to shove her into an electrified fence, and another time by pouring cleaning fluid into Kristine's coffee, he said. She admitted she wanted her new parents dead, he said, and told them she wanted to stab the family to death while they slept.

The Barnetts reportedly had Natalia's birth year legally changed from 2003 to 1989 two years after they adopted her. When they left her in Indiana, they prepaid the rent on her apartment and signed her up for social welfare programs, Michael said.

The couple said they left her behind because they feared for the safety of themselves and their three other children, including physics genius Jacob Barnett whose accomplishments prompted "60 Minutes" to profile him in 2012.

Michael said the family moved to Canada, without Natalia, so Jacob could pursue college studies. Natalia, Michael said, was capable of taking care of herself.

Natalia is now living with another family in Indiana, who reportedly treat her as a teenager.

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