COLUMBIA, S.C. - Attorneys have asked the U.S. Supreme Court to hear the case of a teen sentenced to 30 years in prison for killing his grandparents when he was 12, arguing that the sentence is cruel.

Christopher Pittman used a shotgun to shoot his grandparents, Joe and Joy Pittman, and then set fire to their home in 2001. During his trial four years later, Pittman's attorneys unsuccessfully argued that the slayings were influenced by the antidepressant Zoloft - a charge the maker of the drug vigorously denied.

In the brief submitted to the high court late Monday, attorneys from the University of Texas School of Law argued that the 30-year sentence violates Christopher Pittman's Eighth Amendment protection from cruel and unusual punishment.

Such a lengthy sentence is "unconstitutionally disproportionate as applied to a 12-year-old child," according a copy of the petition provided by the Juvenile Justice Foundation. It said Pittman "is the nation's only inmate serving such a harsh sentence for an offense committed at such a young age."

Zoloft is the most widely prescribed antidepressant in the United States, with 32.7 million prescriptions written in 2003. In 2004, the Food and Drug Administration 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.