Prosecutors say it was that same abuse that led to the death of the boy's sister, Hana Williams.
With the help of interpreters, the young deaf boy explained to jurors the kind of home life he had with his adoptive parents, Carri and Larry Williams.
The 12-year-old, named Emanuel, said he was beaten with a stick and hosed down with with frigid water.
"If the water was really, really cold when it came out I'd be scared," Emanuel said.
The boy's sister, Hana, died two years ago at the family's Sedro-Woolley home. Prosecutors accuse Larry and Carri Williams of starving, beating and neglecting the young girl until she died.
An autopsy showed Hana died of hypothermia brought on by malnutrition. Emanuel described to the jury what a typical meal in the house was like.
"Some of the food, you know, was still frozen," he said. "It wasn't well cooked. You know, it was hard for me to eat.
The day Hana died, prosecutors say she was banished to the back yard. It was raining hard, and the family found her unconscious in the mud a short time later.
Emanuel said he and his sister were often forced outside to eat.
"Well, it was snowing. I couldn't eat at the table. I would have to go under the shelter to eat," he said.
Later in the day, lawyers called family friend Beverly Davies to the stand. Davies said Carri Williams complained how Hana failed to obey her and was routinely spanked.
"She said, 'My house, my children, my rules," Davies said.
Carri and Larry Williams have three biological children, who prosecutors say did not suffer the same abuse as the two adopted kids.
The two youngest boys will not testify, but the oldest will be called to the stand later in the trial.