John Allen Muhammad (search) on Monday became the first person convicted under a unique Virginia anti-terrorism law enacted after Sept. 11, all but guaranteeing the statute will be put to the test on appeal.

Defense lawyers will almost certainly argue that the law is too vague to have been used to convict Muhammad in the sniper slaying of Dean Harold Meyers (search) at a gas station.

The anti-terrorism law, passed by Virginia lawmakers last year, makes a killing punishable by execution if the crime was intended to intimidate the public or influence the government.

Prosecutors argued that Muhammad and his alleged accomplice, Lee Boyd Malvo (search), tried to intimidate the public in the Washington area in order to extort $10 million from the government. They portrayed Muhammad as the "captain" of a two-man "killing team."

Other states have anti-terrorism laws, but Virginia's is the only one with the "mastermind clause," said Tim Murtaugh, spokesman for Virginia's attorney general. The clause means that someone could be convicted of a capital offense for orchestrating a murder even if the person did not actually commit the killing.

In Muhammad's case, the defense argued that there was no evidence that he fired the shot that killed Meyers.

The case will automatically be reviewed by the Virginia Supreme Court if he is sentenced to death, and an appeal is likely even if he gets life imprisonment.

"The fact that it's the first case under this new and untested law guarantees the appellate court will look hard at the application of this statute," said Anne Coughlin, a University of Virginia law professor.

Virginia Attorney General Jerry W. Kilgore, a Republican who drafted the legislation, said he believes the law was applied correctly to Muhammad.

"It was written in response to and in the aftermath of 9-11, but it was written broadly enough to include individuals who terrorize a community," he said. "The snipers terrorized an entire state. People were afraid to go to the mall, afraid to take their kids to school, afraid to pump gas."

But whether prosecutors proved he was the mastermind of a terrorist act, with enough control over Malvo to command the killings, is questionable, some lawyers said.

"The question has always been whether (the law) includes the type of psychological relationship that may have existed here between Muhammad and Malvo," said Richard Bonnie, a criminal law professor at the University of Virginia.

Defense attorneys have argued that the law is worded so vaguely that any crime that produces fear in a community could be prosecuted as terrorism, rendering the statute unconstitutional.