What to Know
Police say mother's arrest is due to leaving the child home alone, not necessarily related to death investigation.
Child's body found two weeks after she was reported missing; father later said she choked on milk and he moved her body.
Couple's biological child remains in foster care; hearing set for Nov. 29 to determine custody.
The mother of a North Texas toddler whose body was recovered last month from a drainage culvert weeks after she was reported missing was arrested Thursday on a charge of child endangerment.
Police said she and her husband left their 3-year-old adopted child, Sherin Mathews, home alone while they went to dinner just hours before they claimed she had disappeared.
Sini Ann Mathews, who has maintained her innocence in the death of Sherin, surrendered to Richardson police Thursday and is being held on $250,000 bond on the state jail felony charge.
She was arraigned Friday morning and did not respond to reporters questions when she was transferred to the Dallas County Jail Friday afternoon.
In a statement Thursday, Richardson police said detectives learned Sini Mathews, 35, and Wesley Mathews took their 3-year-old biological daughter to dinner and left Sherin alone at home, placing her in "imminent danger of death, bodily injury, or physical or mental impairment."
"The time that they left, she was not under the care of any other adult or of any other person, she was left home alone by herself and it's for that reason that you see this particular charge," said Kevin Perlich, with the Richardson Police Department. "It's not necessarily related to her death, it's related to her care that she was being given while she was in that home."
According to an arrest warrant affidavit, detectives used cell phone records to show Wesley and Sini went to a North Garland restaurant on the evening of Oct. 6. The theory is supported by a receipt obtained by police that showed the couple purchased only one child's meal in addition to their individual meals as well as the testimony of a waiter who said only one child was present at the table.
During an interview with detectives, Wesley Mathews, 37, admitted to leaving Sherin home alone after growing frustrated she wouldn't drink her milk and said they returned home about 90 minutes later and found her where they left her, in the kitchen.
Both Sini and Wesley told police the child was alive when they returned home from dinner, though police have not confirmed that information.
Hours later, on the morning of Oct. 7, Wesley Mathews called police and reported Sherin missing. In a story he would later change, Wesley originally told police Sherin disappeared overnight after he ordered her to stand outside at about 3 a.m. for not drinking her milk. When he returned, Wesley said she had disappeared and that her location was unknown.
Weeks later, Wesley Mathews changed his story and said he "physically assisted" her in drinking her milk and that she choked and died at the home. He said he then moved the girl's body and later called police to report her missing.
The Dallas County Medical Examiner's Office is still working to determine what killed Sherin Mathews.
Sini Mathews said she was sleeping when Sherin disappeared and was unaware of what took place overnight between the child and her father.
Meanwhile, Wesley Mathews remains jailed on a charge of felony injury to a child and is being held on a $1 million bond.
NBC 5 confirmed Friday that at some point in the last month Sini Mathews was terminated from her job at Children's Medical Center in Dallas where she worked as a case manager.
On Thursday, her attorney Mitchell Nolte thanked Richardson police for allowing his client to surrender.
"We learned this morning that the Richardson Police Department had obtained an arrest warrant for Sini Mathews for the offense of Abandoning/Endangering a Child. The police were professional and courteous and allowed us to bring Mrs. Mathews to the Police Department and surrender herself into custody," Nolte said in a statement.
Earlier this week, Wesley Mathews' attorney, David Kleckner, said his client loves his children and wife and that he's a good family man who wants custody of their surviving daughter to be returned to her mother.
Sini Mathews was in court as recently as Monday asking for custody of the couple's child to be returned to her, but that hearing was rescheduled 1 p.m. Nov. 29. The couple's surviving child has been in foster care since shortly after her sister's disappearance. The child was expected to be placed in the care of family in the Houston area following Monday's hearing.
NBC 5's Diana Zoga and Maria Guerrero contributed to this report. Check back and refresh this page for the latest update. As this story is developing, elements may change.