Prince William County prosecutors never proved that John Allen Muhammad fired the bullet that killed Dean H. Meyers during the 2002 sniper rampage in the Washington area, so the trial judge should not have allowed a jury to consider the death penalty, Muhammad's attorneys argued in their appeal this week to the Virginia Supreme Court.

The legal claim by Muhammad's defense team is one of 102 "assignments of error" raised in a 140-page brief filed late Monday in Richmond. The brief is the beginning of what could be a long appeals process that could lead to the federal court system and last for years.

Muhammad, now 43, and Lee Boyd Malvo, 19, were arrested in a parked car in Frederick County after 13 people had been shot, 10 fatally, during a three-week period in October 2002. The rifle believed to have been used in all the shootings was found in the car, along with a laptop computer mapping out the locations of some of the killings.

Malvo's fingerprints and skin cells were found on the rifle, and the teenager admitted firing the gun in conversations with jail guards and investigators. But Muhammad did not talk to investigators, and no physical evidence linked him to the rifle.

The two suspects were tried separately in different counties. Prince William prosecutors called Muhammad the mastermind of the shootings, and Fairfax County prosecutors said Malvo was the triggerman.

Prince William Commonwealth's Attorney Paul B. Ebert argued that Muhammad's role made him equally responsible for the shootings and that he deserved to die. Peter D. Greenspun and Jonathan Shapiro, Muhammad's attorneys, said that under Virginia law, only the shooter was eligible for the death penalty.

Prince William Circuit Court Judge Leroy F. Millette Jr. ruled for the prosecution.

"I think a fair inference can be drawn that they perfected their ability to shoot people and perfected their ability to shoot them and escape," Millette said in his ruling. "I think that an inference can be drawn that the vehicle itself was instrumental in their ability to do that; and it took two people to position that vehicle in situations so that they could complete the shooting and escape undetected."

Millette's ruling was arguably the most controversial legal decision in the case. Greenspun and Shapiro contended in their appeal that Virginia law states with "unambiguous precedent" that "only the actual killer . . . is eligible to receive the death penalty. There is absolutely no evidence of Mr. Muhammad's guilt as the actual perpetrator, that is, the triggerman."

The defense also argued that Millette improperly allowed victim impact testimony from the friends and family of Meyers and Linda Franklin, the shooting victim in Fairfax. The emotional 911 call by Franklin's husband, William, was played to the jury during the guilt phase of Muhammad's trial. In Malvo's trial for Franklin's killing, Fairfax Circuit Court Judge Jane Marum Roush did not allow the tape to be played during the guilt phase. It was played during the penalty phase, however.

"Nothing relevant to the crime was provided by Mr. Franklin," Muhammad's defense argued, saying it was "an effort to excite the passions of the jury regardless of the lack of facts." The defense noted that other victims' relatives also testified improperly during the guilt phase. Prosecutors said it was done to show the impact of terror.

The sniper trials provided the first test of a new Virginia anti-terrorism statute, which Muhammad's attorneys argue is unconstitutionally vague. The law prohibits intimidating the civilian population or influencing the conduct of the government. Prosecutors said the snipers did both by inflicting fear and by demanding payment to stop the shootings.

The defense said the definition of terrorism is far too fuzzy. "There is an enormous difference between criminals who 'terrorize' and 'terrorists,' " Greenspun and Shapiro wrote. "But the statute as drawn fails to draw that distinction, allowing instead unguided and unbridled law enforcement discretion."

The defense also renewed its argument that the prosecutors in the two sniper trials improperly used conflicting theories of the case, though they represent one entity, the commonwealth. Greenspun and Shapiro note that Ebert portrayed Muhammad as controlling and directing Malvo. But Fairfax prosecutor Robert F. Horan Jr. said Malvo was independent and intelligent.

The Virginia attorney general's office will file a reply brief for the prosecution. Oral arguments in the case could be heard this fall.

John Allen Muhammad's defense said the law requires proof that Muhammad was the triggerman.