JACKSONVILLE, Fla. -- A man accused of locking his 9-year-old son in a room and treating the child like a prisoner has reached a plea agreement.

Prosecutors announced on Thursday that Randall Piercy would be at the Duval County Courthouse in four weeks to plead guilty to aggravated child abuse charges.

In 2006, Piercy was arrested after police said they found his youngest son locked in a bedroom that smelled of urine. Investigators said the boy was allowed out only once a day to go to the bathroom, didn't go to school, didn't get medical attention and wasn't allowed to have friends.

Police said the father had video cameras in almost every room to monitor the boy's actions.

Piercy admitted on "Dr. Phil" that he taped the light switch in the boy's room so the child couldn't turn on the lights. Piercy said he did that because the boy had been burning things on the light bulb. He also admitted on the show to taping the boy's window shut.

"What he did -- he had opened the window and decided he wanted to crawl out on the roof and I had to run out and catch him," Piercy said on "Dr. Phil."

Prosecutors said the only real explanation Piercy has ever given was to Phil McGraw and not to them.

With his guilty plea, Piercy could face as many as nine years in prison. Prosecutors said they might show the Dr. Phil Show interview to the judge because they said Piercy made himself look worse than they ever could.

The boy at the center of the child abuse case is now 11 years old. Channel 4 has learned he is living in foster care.

"We're committed to providing the help that the child needs, and certainly he is getting services and counseling. He has been through a lot, but he is living a fairly decent life. I mean, he's doing well. He's going to school," said Department of Children and Families spokesman John Harrell.

Piercy's wife, Michelle Piercy, was arrested days after her husband was taken into police custody.

"Yes, my husband is a little controlling. Yes. He's a little controlling. Yes, I am a little controlling," Michelle Piercy told Channel 4 shortly before her arrest.

Prosecutors said they have always believed Randall Piercy was more to blame for what happened to the child than his wife. They said in the end, Michelle Piercy could also end up reaching a plea deal.