Jurors began deliberating Monday in the murder trial of a 15-year-old boy who claims the antidepressant Zoloft (search) drove him to kill his grandparents three years ago.

The trial has been billed as the first case involving a youngster who says an antidepressant caused him to kill. The trial also comes at a time of heightened scrutiny over the use of antidepressants among children.

Defense attorneys urged the jury Monday to send a message to the nation by blaming Zoloft for the killings by 15-year-old Christopher Pittman (search). They said the negative effects of Zoloft are more pronounced in youngsters, and the drug affected Pittman so he did not know right from wrong.

"We do not convict children for murder when they have been ambushed by chemicals that destroy their ability to reason," attorney Paul Waldner said.

But prosecutors called the Zoloft defense a smokescreen, saying the then-12-year-old Pittman knew exactly what he was doing three years ago when he shot his grandparents, torched their house and then drove off in their car.

Prosecutor Barney Giese said the real motivation for the crime was the boy's anger at his grandparents for disciplining him for choking a younger student on a school bus. And he reminded jurors how the boy carried out the killings — shooting his grandfather in the mouth and his grandmother in her head while both lay sleeping.

"That anger ... came bubbling up — came bubbling up like gas out of an oil pit," the prosecutor said. "I don't care how old he is. That is as malicious a killing — a murder — as you are ever going to find."

Prosecutors also pointed to Pittman's statement to police in which he said his grandparents "deserved it."

"They did not deserve those pellets in their brains," Giese said as he turned toward the defendant. "No, Chris Pittman, they did not deserve it. They deserved better."

The jury deliberated for about four hours Monday before going home for the day.

Pittman has not denied carrying out the slayings. He is charged as an adult in the November 2001 murders of Joe Pittman, 66, and his wife Joy, 62. If convicted, he could get 30 years to life in prison.

Zoloft is the most widely prescribed antidepressant in the United States with 32.7 million prescriptions written in 2003. Last October, the Food and Drug Administration (search) ordered Zoloft and other antidepressants to carry "black box" warnings — the government's strongest warning short of a ban — about an increased risk of suicidal behavior in children.

Pittman threatened to kill himself about a month before the slayings. He also ran away from home.