Joe Pittman's hands shook as he read his son's confession to a roomful of strangers during a Food and Drug Administration (search) hearing in Washington.

"I took everything out on my grandparents, who I loved so very much," wrote then-12-year-old Christopher Pittman (search). "When I was lying in my bed that night, I couldn't sleep because my voice in my head kept echoing through my mind, telling me to kill them."

Authorities say Christopher shot his grandparents as they slept in their rural home three years ago because they had scolded him for fighting on the school bus.

Joe Pittman thinks his son killed because his sense of right and wrong was clouded by the anti-depressant Zoloft (search). He spoke out against the drug in a hearing early this year. The boy, who had threatened suicide, was put on the drug three weeks before the slayings, and his dose was doubled just two days earlier.

But prosecutors and police say Christopher's actions during and after the November 2001 slayings show he clearly knew what he was doing was wrong.

The boy waited until his grandparents were sleeping and took a pump-action shotgun from a gun cabinet. He crept into the couple's dark bedroom, first shooting 66-year-old Joe Frank Pittman in his open mouth, then firing into the back of 62-year-old Joy Pittman's head.

Christopher then set the house on fire and drove off in the family car. When he got stuck on a dirt road 20 miles away, he told hunters he was kidnapped by a man who killed his grandparents, set the fire, drove him into the woods and ran away.

Christopher was living with his father's parents in hopes of turning his life around. He told defense experts he felt abandoned by his mother and his relationship with his father was rocky. No one answered phone calls to Joe Pittman's home.

A month before the slayings, Christopher was hospitalized in Florida, where his father lives, after he threatened to kill himself. The boy was prescribed the anti-depressant Paxil, but another doctor soon put him on Zoloft instead.

Pittman decided to send the boy to live with his grandparents in Chester County, a rural area between Columbia and Charlotte, N.C.

Christopher, who turns 16 in April, is being prosecuted as an adult and faces 30 years to life in prison if convicted at his trial, set to start next month. His lawyers argue that his case should be moved to Family Court, where if convicted, he could only be kept in custody until he turns 21.

Karen Menzies, one of Christopher's lawyers and an attorney specializing in lawsuits against anti-depressant makers, said medical research is available to support the Zoloft defense.

In the three years the teen has spent in jail awaiting trial, the FDA has become increasingly wary of doctors prescribing Zoloft and other antidepressants for children.

In October, the agency ordered the drugs to carry "black box" warnings -- the government's strongest warning short of a ban -- about increasing the risk of suicidal behavior in children.

"The science has been out there for a while. The prescription drug companies have been able to hide it," Menzies said.

On the other side is Pfizer Inc., the maker of Zoloft, which has aided the prosecution, according to Solicitor John Justice, who has since taken himself off the case for health reasons.

The company has vigorously fought cases claiming antidepressants cause violent or suicidal behavior.

A spokesman responded to inquiries by pointing out an October statement on the company's Web site addressing concerns of suicide attempts, saying studies show "no statistically significant difference" between children using Zoloft and nonusers. The statement, though, does not discuss any possible link between the drug and violent acts against others.

Trying to blame a drug for causing someone to commit a crime is an uphill fight, but it has been done successfully.

In April, a Santa Cruz, Calif., jury acquitted a man of attempted murder after he beat his friend, then blamed the episode on Zoloft.

National Association of Criminal Defense Lawyers spokesman Jack King said the "Zoloft-made-me-do-it" defense likely means that the Pittman case will come down to defense vs. prosecution experts.

"It's going to be a battle of whose experts the jury believes," King said.

Christopher's maternal grandmother, Delnora Duprey, of Wildwood, Fla., said her grandson is no longer on any medication and is the "sweet, quiet, laid-back" boy she knew growing up. "He's the old Christopher again."

Menzies said the teenager is getting good grades and behaving behind bars.

Duprey says the "whole entire family is behind Christopher 150 percent."

She thinks Zoloft had to have caused Christopher to kill his grandparents because he loved them both, especially the grandfather he called "Pop-Pop."

"We used to joke that he was his Pop-Pop's shadow," Duprey said.

However, those who dealt with the boy after the crime feel differently.

"Anybody who could kill his grandparents in the fashion he did shouldn't be let loose on the public at age 21. And that would have been the best-case scenario," said former prosecutor Justice, who pushed to move the case to adult court.

The current prosecutor, Barney Giese of Columbia, said through his office that he doesn't talk about cases before they go to trial.

Chester County Sheriff Robbie Benson said interviews with Christopher left him shaken because he could not believe the lack of remorse. "This was cold-blooded."

Menzies said those observations might help her case.

"The boy was still suffering from the side-effects of this medication after the incident," she said. "I think we see a different Christopher now."