Ingrid Brewer is charged with eight felony counts, including torture, cruelty and assault with a deadly weapon.
She had plead not guilty.
The 50-year-old woman was arrested in January after the 7-year-old girl and her 8-year-old brother were found bruised and beaten on a street, huddled under a blanket in 20-degree weather.
The children had run away to escape abuse, authorities said.
In court on Tuesday, Sheriff’s investigators testified that Brewer zip-tied the children’s wrists, beat them with a plastic jump rope, and locked them in separate rooms while she was away – sometimes for as long as 12 hours.
After Brewer’s arrest, county investigators uncovered a history of child maltreatment investigations involving Brewer going back to 2001, when callers to a hot line twice reported that she was abusing her two biological children.
Both times, social workers concluded that the allegations were unfounded.
After visiting Brewer’s Palmdale home while assessing her application to adopt the children, the social worker reported that the children appeared stiff in Brewer’s presence and had to ask permission to do anything.
The girl told a social worker she was scared.
Despite that report, the Los Angeles County Department of Children and Family Services looked no further and contact with the family was soon terminated.
Brewer is due back in court March 19 for pretrial motions.