Lena Marie Lunsford Conaway, 35, faces multiple charges in the September 2011 disappearance of Aliayah Lunsford, whose body has never been found.
Lewis County Prosecutor Christina Flanigan told jurors in opening statements that Conaway refused to get help for the girl, media outlets reported.
Conaway is charged with murder of a child by parent by failure to provide necessities, death of a child by parent by child abuse, child abuse resulting in injury and concealment of a dead body. She now lives in Florida.
One of the victim's sisters, the first witness called to testify, said Aliayah Lunsford had been placed in a corner as punishment when she saw her mother hit her younger sister with a broken bed slat.
The sister said she and another sibling the next morning checked on Aliayah, who wasn't responsive. They told their mother, who tried to revive her.
Instead of calling authorities, their mother put Aliayah's body in a laundry basket, put clothes on top of her and drove to the woods where the body was placed, the girl testified.
Conaway's husband at the time was at work when the body was disposed of and was unaware that Aliayah had been struck, the girl testified. She said her mother told the girls not to reveal what happened.
The girl said that in 2016, she looked at her adoptive father and said, "I know where Aliayah is." Authorities were never able to find the body.
Defense attorney Tom Dyer said in his opening statement that in 31 years, "without question this is the ... most twisted and bizarre, most complicated case I've ever been involved in."
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