Mayra Rosales was nicknamed the “half-ton killer” after she claimed to have killed her 2-year-old nephew by accidentally sitting on him. The south Texas woman was acquitted of the crime after she recanted the story and her younger sister was found guilty of child abuse, but Rosales’ journey to freedom had just begun.

Rosales, of La Joya, near the Mexican border, explained in an interview with ABC's "Nightline" that she only tried to take the rap for her sister in the first place because she believed she was going to die anyway.

"I tried to protect my sister, and I was already dying, so I didn't see ... like I was doing [something] wrong," she said. "I was already giving up in life, and the way I saw it, when they began saying I was going to get capital murder charges, I really saw it like they were doing me a favor."

Now her sister Jamie is serving 15 years in prison for the death of her son, little Eliseo Rosales Jr. She also wants Mayra to have custody of her other three children while she is in behind bars.

In 2008, with cameras filming every second of her murder trial, Mayra Rosales weighed 1,200 pounds. She took up a whole king-sized bed to herself and needed to be cut out of her bedroom to attend her court proceedings. "I couldn't even stand up on my feet,” she told Nightline. “My legs couldn't hold my weight."

Autopsies of her nephew showed that it was impossible for the “half-ton killer's” story to be true. Eliseo had suffered from repeated blows to the head. While Jamie has been serving time for the young boy’s murder, Rosales has been working hard on herself and undergone a metabolic metamorphosis.

TLC was there with their cameras to catch the Texan's journey. Doctors told her she needed to lose 600 pounds before they considered gastric bypass surgery. In her first week she lost 100 pounds. After various surgeries to remove tumors and excess skin, in addition to maintain a high-protein diet, Rosales has lost 800 pounds. She says she is practically in perfect health and has been searching for a job.

"I think it's a miracle of God that I'm healthy," she said. "I'm alive, and I'm not diabetic. I do not have cholesterol [problems]. I don't have high blood pressure, so I'm healthy."

Rosales’ special, "Half-Ton Killer: Transformed," will air Wednesday on TLC at 9/8c.

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