A teenager who ran from a Northern California home wearing a shackle on his ankle endured frequent beatings, sometimes in front of other children, that worsened over the year he spent there, according to grand jury testimony made public Friday.

The 970-page transcript includes testimony from the teen, the alleged abusers' children, social workers, police officers and about three dozen other people who had knowledge of the events.

The emaciated boy was 16 when he escaped the house in Tracy in December and stumbled into a nearby fitness center, nearly naked and covered in filth. His physical condition was so bad that he required skin grafts to repair burn damage all over his body, according to a doctor who testified before the grand jury.

Homeowners Michael Schumacher and Kelly Layne Lau; the teen's one-time guardian, Caren Ramirez; and neighbor Anthony Waiters have pleaded not guilty to multiple charges, including torture, aggravated mayhem, torture and false imprisonment.

A gag order is in place, preventing both sides from discussing the case.

The boy told the grand jury in March that Ramirez and Lau beat him for infractions such as forgetting to water the lawn or not cleaning the bathroom properly, the court documents said. He said they initially hit him with their hands, but that eventually escalated to belts, a mallet, a hammer and an aluminum baseball bat.

The teen testified that his abusers often had conversations in front him about torturing and killing him.

"I remember they said they would try to, like cut me up and everything and throw me in the delta, and one time he, Michael, asked Kelly for a syringe so he could, like, pump air into my veins and stuff like that," he testified, according to the documents.

The teen said Waiters once sliced his arm with a knife while Ramirez held him down and Lau watched.

"`You better not scream or anything,"' the boy said Waiters told him. "They just told me to shut up."

The teen said Ramirez poured bleach and salt on his open wounds.

Prosecutors say the boy began receiving regular beatings shortly after arriving at the Tracy home. By January 2008, they say, he was being chained up in various rooms in the house.

Two of Schumacher and Lau's four children — ages 5 and 9 — testified that the boy regularly was denied food and that his diet consisted of candy bars and water. They said the hungry teen often was reprimanded for trying to take food from the refrigerator.

At one point prosecutors asked the 5-year-old girl what prompted the poor treatment.

"He would think he was the boss of us and do bad stuff at the house so that's why he got chained to the table," said the girl, who was not named in the transcript.

She said her mother and father hit him with a baseball bat "hard. Like in the head, on the legs, on the arms."

The girl testified that the teen became bloody from the beatings and that she heard him scream and cry. She also said her mother told her not to tell anyone what she'd seen.