A teenager who unsuccessfully blamed Zoloft (search) after slaying his grandparents never should have been tried as an adult and should have his 30-year prison sentence cut to probation, his lawyers argued.

Defense attorney Andy Vickery argued in a motion filed Wednesday that trying Christopher Pittman (search) as an adult for a crime committed when he was 12 violated the Constitution's prohibition of cruel and unusual punishment.

Pittman, now 15, was convicted and sentenced last week for shooting Joe Pittman, 66, and his wife, Joy, 62, in 2001 and burning down their home. The judge's only choice in sentencing under the law was life behind bars or 30 years.

The defense argued at trial that Pittman was involuntarily intoxicated by the anti-depressant Zoloft when he killed the couple and couldn't tell right from wrong.

Vickery claimed Wednesday that the crime was committed before the part of Pittman's brain most often associated with criminal culpability had fully developed.

"How then can a civilized society assess the same culpability for, and impose the same punishment on, a 12-year-old as you would impose on a grown man?" Vickery asked.

The motion seeks credit for the more than three years Pittman has been in custody and asks that he be placed on probation until he reaches 21.

Vickery had tried to have the trial moved to Family Court before it began, but Circuit Court Judge Danny Pieper denied the motion, calling it premature.

In another motion Thursday seeking a new trial, Vickery wrote that a juror violated Pieper's order not to discuss the case outside the jury room.

Prosecutors had no immediate comment on either motion.