In a new interview, Mayra Rosales, 31, of Texas, says she could not have hit the boy on the head because her arm was so big that she would not have been able to lift it to strike him.
When two-year-old Eliseo Jr died in March 2008, 74-stone Ms Rosales, who had been babysitting at the time he was taken into hospital, originally claimed she caused his death by falling onto him.
Accused: 74-stone Mayra Rosales stood trial for the murder of her two-year-old nephew after covering for her abusive sister
But after doctors revealed the death could only have been caused by a blow to the head, Ms Rosales confessed that she had invented the story to protect her sister Jaime, whom she claimed had struck the boy various times over his body with a hairbrush earlier the same day.
Mayra and her husband Bernie had recently moved in to live with sister Jaime, who had undertaken a full-time role caring for her when Mayra became so large she struggled to walk.
Despite the fact that Mayra was almost entirely bed-ridden, Jaime would often go out, leaving Mayra in charge of her four children.
'I was more of a mother than Jaime,' Mara said in an interview with Reveal magazine. Whenever she wanted to go out or go shopping, she didn’t take the kids. She would always leave them at home with me.'
But events took a horrific turn in March 2008, when Mayra witnessed her sister hit Eliseo Jr. ‘Jaime was giving my nephew breakfast and he didn’t want to eat,’ says Mayra. ‘I told her if he was crying he wasn’t going to eat, but she got mad, got a brush and hit him on his arms, legs and head which left a bump. Afterwards, she got his Winnie the Pooh blanket, covered him up and put him to bed. Then she went out, leaving me with the children.'
Later that day, Eliseo Jr began suffering from breathing problems and Mayra phoned for an ambulance. Jaime phoned her sister from the hospital, sobbing that the police would not let her see her son unless she told them who had hurt him. Jaime begged Mayra to tell the authorities she was responsible for the injuries.
In a move she would come to bitterly regret, Mayra accepted.
Murdered: An autopsy revealed that Eliseo Jr, left, was killed by a blow to the head, not by being crushed in a fall
‘People may not understand this but I wanted to help my sister and I didn’t want the authorities to take the other children’ says Mayra.
‘I told the investigators that I rolled over to the edge of my bed to where Junior was and my hand slipped and I fell on him with my hand. I fell. I was the one to blame. But only by accident.'
Mayra was subsequently arrested and charged with capital murder. But as the trial progressed, the court heard that the fatal injuries sustained by the boy were consistent with a blow to the head and could not have been caused by someone falling on him.
'It would have required her to have to swing her arm to strike the child on the head but she could never move her arm in that manner,’ says Mayra’s lawyer Sergio Valdez.
‘We knew that her size was her best defence because she couldn’t move her arm.'
Despite the physical impossibility of Mayra committing such a crime, the authorities had to conduct a full trial, with Mayra as the chief suspect.
Months went by before a courtroom was found that was large enough to accommodate Mayra, and doors and walls had to be removed to fit her in.
Finally, Mayra could testify. But as a result of her testimony, Jaime went on the run, leaving Mayra facing the possibility of a death sentence.
‘I wasn’t surprised,’ says Mayra. ‘Jaime is into a lot of bad things and I understood why she did it.’
As the trial date approached, prosecutors became suspicious at Mayra's account that she fell on Eliseo Jr. Mayra decided at that point to come clean with a confession that would incriminate her sister.
Abusive: Jaime Rosales was found guilty of causing injury to a child and sentenced to 15 years in jail. Her remaining three children, fathered by boyfriend Eliseo Sr, right, are now being cared for by their grandmother
Testifying from her bed at home under oath, she admitted that Jaime was behind the abuse.
‘We were all trying to cover for my sister,’ she says. ‘There was abuse from her towards her son. She yelled at him. She kicked him. On that night Junior didn’t want to eat and she got frustrated and she hit him on the head with a hairbrush. I thought I was dying anyway so I decided to admit that I’d done it to protect my sister because I love her.’
Ill-health: Mayra, who has lost 20st since being admitted to a hospital for the super-obese, now needs round-the-clock care
A few months later, Jaime was persuaded to return to Texas where she stood trial for her son’s murder.
Pleading guilty to the lesser charge of causing injury to a child, she was sentenced to 15 years in jail.
The stress of the case caused Mayra's health to deteriorate to the point that she had to be admitted to a hospital for the super-obese, where she remains today, confined to a hospital bed. When a regular ambulance was too small to transport her, a removal truck had to be used.
‘I began retaining more water in my legs and they got so hard,’ she says. ‘The skin is so stretched out that it hurts. It feels like my legs are going to pop like a balloon. Sometimes the sores open up and water oozes out. I wondered if we should amputate.
'Sometimes I got mad. I tried not to show it that much because I didn’t want anyone feeling bad for me. It was like I was in prison, with chains holding me there so I couldn’t move.’
Mayra has suffered chronic skin infections around her body caused by the folds of fat in her skin, and doctors attempting to treat her have removed several litres of fat and fluid from around her body.
In the first 12 weeks of hospital treatment she shed 20 stone.
Doctors have told Mayra she still has years of treatment ahead of her. Against all odds, Mayra manages to look to the future with optimism.
‘I’m really sad that my sister is in jail but I think my sister understands now that her actions were wrong. I believe she can change and learn from what happened. Today it’s like I’m getting a new chance. I never gave up on hope and faith that some day my life will change.’
Accused: The 74 stone Babysitter is on Channel 4, tonight, 3 January at 9pm.
Read the full interview by Jill Foster in this week's Reveal magazine, on newsstands now.