Houston: The mysterious death of three-year-old Sherin Mathews in Richardson, Texas, in 2017, took a new twist on Friday with a Dallas court dropping child abandonment charge against her foster mother Sini Mathews, a Keralite from Ernakulam district.

Sini Mathews, accused in the death of her adopted daughter Sherin Mathews, was acquitted by Dallas County district attorney's office for want of evidence. However, her husband Wesley Mathews is still in jail facing the charge of felony injury to a child, which carries a sentence of up to life in prison, as his trial is yet to begin in a court. Trials of Sherin and Wesley are conducted separately.

Sini was charged with child abandonment for allegedly leaving Sherin home alone on the night of her death. Her husband, Wesley, is accused of killing the three-year-old girl, who was adopted from an orphanage in Bihar in 2016.

Sherin was found dead under a culvert near the family's home in Richardson, Texas, on October 22, 2017, two weeks after her family reported her missing. Wesley initially told the police that his daughter had gone missing from outside the house. He had made her stand outside the house at 3am as punishment for not finishing her milk. Sherin was missing when he went back for her, Wesley had contended.

He changed his story later and told investigators that Sherin died after choking on milk. He admitted to putting her body under the culvert near their home in Richardson in suburban Dallas.

The Dallas County Medical Examiner's Office which released Sherin's autopsy report listed the cause of death as homicide and the manner as homicidal violence. Both Wesley and Sini were lodged at the Dallas County jail. Their four-year-old biological daughter is staying with relatives in Houston.

The story of Sherin's whereabouts and her tragic death in 2017 made headlines worldwide.

The investigating agencies had found that one of the three cars at the Mathews' residence had gone out of the premises on the same night when little Sherin reportedly went missing. With the evidence pointing that the child was killed and body taken out in a car and dumped under the culvert ,Wesley Mathews was charged in the case.

Sherin, who had developmental issues and limited verbal communication skills, was last seen outside her family's backyard in Richardson, Dallas, at 3.15am.

US child protection authorities had earlier stated that they had found "insufficient evidence" to confirm that Sherin was physically abused by her adoptive parents and blamed "an unknown perpetrator" for her injuries, prior to her adoption.

Sherin's decomposed body was found by a cadaver dog. Wesley had admitted that the family had gone out for dinner that night and left Sherin home alone.

Sini, if the charges were proved, would have faced a punishment ranging from two to 20 years in prison with a fine up to $10,000. Friday's verdict has allowed her to walk out free.

A Child Protective Services (CPS) report had detailed the agency's investigation into allegation that Sherin's adoptive parents abused her months before she died.

The report detailed a CPS investigation from March 2017.

The CPS said it found "insufficient evidence to determine if the deceased child was physically abused by her mother."

"An unknown perpetrator was confirmed for the physical abuse...which may have happened prior to her adoption," the report said.

"The allegation of physical neglect of the deceased child by her parents was not confirmed," the report said.

Dr Suzanne Dakil, a paediatrician, testified during a custody hearing for Sherin's sister had said that she was the one who called the CPS in March last year with concerns that Sherin was being abused by her parents.

"I tried, actually, very hard to find another good explanation, and I didn't have one," the doctor said in court, noting that she concluded Sherin's injuries had occurred after her time in India.

Dakil's clinic in Dallas had been treating Sherin for her weight problems.

Sherin was hospitalised in February 2017 after her adoptive mother "noticed swelling around (Sherin's) right shoulder".

Sini reported that Sherin had fallen on a slide at the park. Doctors diagnosed Sherin with a skin infection and fractures on her shoulders, and X-rays revealed a previous injury, a fracture of her left leg.

"There were concerns that the child's injuries were not consistent with the explanation given and that the child had been physically abused."

The CPS interviewed Sherin's parents, who "denied harming the child."

Sini said she had taken Sherin to a park, where she fell and her mother tried to grab her arm to break the fall.

Wesley told investigators that Sherin slipped and fell while on monkey bars at the park.

When asked about Sherin's previous arm fracture, Sini told CPS officials that Sherin fell while jumping on the couch with her sibling.

The CPS contacted medical officials, who "stated there were no concerns about the previous injury because the story was consistent with the child falling off the couch."

The medical officials said the fractures in Sherin's shoulder injury were "questionable.

The issue of Sherin's weight was also raised in the investigation.

Both parents said Sherin had health problems when they adopted her from India, including being underweight.

Doctors who had treated Sherin "denied having concerns about abuse and neglect while the child was with her adoptive parents" and that Sherin was in better health and at a better weight following her adoption."

Law enforcement authorities investigated the report but did not file charges.