Authorities in Virginia yesterday filed capital murder charges against the suspects in the Washington area sniper shootings as doubts grew that prosecutors in Maryland could secure the death penalty against them.

Prosecutors in Prince William, Hanover and Spotsylvania counties used Virginia's new anti-terrorism law for the first time, charging that John Allen Muhammad, 41, and John Lee Malvo, 17, carried out the shootings to intimidate the public or influence the government. By using the statute, which went into effect in July as a response to the Sept. 11 attacks, Virginia could obtain the death penalty without proving who fired the fatal shots, prosecutors said.

In addition, Justice Department sources said last night that federal prosecutors plan to file charges against Muhammad and Malvo related to the sniper attacks as soon as this afternoon, a move that would add to the uncertainty over where a trial might take place. The charges probably would be brought in Greenbelt, government sources said.

Investigators across the country continued yesterday to try to piece together Muhammad's and Malvo's movements, hoping to determine who fired the rifle that killed 10 and wounded three in a series of shootings that terrorized the Washington region this month.

The FBI was fielding calls from police departments in states where the pair traveled. The local departments were seeking evidence that might link the suspects to unsolved killings and robberies in those jurisdictions.

But for now, the focus is on the Washington region, where charges against Muhammad and Malvo are building. Yesterday's indictments were the first filed in Virginia since Muhammad and Malvo were captured last week, and they follow similar charges filed Friday in Montgomery County.

With charges now pending in several jurisdictions, there is a messy debate over where the pair would be prosecuted first -- a debate that will be settled by U.S. Attorney General John D. Ashcroft. Several sources said the arguments are focusing on the likelihood of securing the death penalty.

In that respect, there is widespread agreement that Virginia, which has executed more people than any other state besides Texas and where Malvo would be eligible for execution despite his age, has the upper hand.

"The death penalty is reserved for the worst of the worst," said Prince William Commonwealth's Attorney Paul B. Ebert. "This may be the most heinous case that I've ever prosecuted. The effect it has had on the entire area is mind-boggling and devastating. If someone deserves to receive the maximum punishment available, these folks appear to be them."

Maryland courts are more likely than those in Virginia to overturn death sentences, fueling the belief that Montgomery County would not get the first trial.

There also is concern that the sniper shootings do not meet Maryland's standard for a capital crime. One of 10 aggravating circumstances must be present for the jury to consider the death penalty. In this case, legal experts said, the only applicable circumstance would be if there was more than one killing "arising out of the same incident."

But Maryland law does not define "same incident," legal experts said, and there are no appellate court decisions strictly defining the term.

Baltimore County State's Attorney Sandra O'Connor, whose office has tried more capital cases than any other in Maryland, said the four killings in Montgomery County on Oct. 3 do not quality as the same incident.

"They went from one place to another to another," O'Connor said. "If you go into a 7-Eleven and kill one person and then go down the street to another 7-Eleven and kill another person, that is two incidents" under Maryland law.

Montgomery County Executive Douglas M. Duncan said in an interview yesterday that he does not have a preference about where the case is tried. He urged prosecutors to present a unified front for the public.

"Wherever you have the strongest case and the stiffest penalties is where the case should go," he said.

Perhaps complicating the decision are the pending federal charges. Two Justice Department officials said prosecutors would use provisions of the Hobbes Act -- which prohibits the use of extortion or threats of violence to disrupt interstate commerce -- to charge Muhammad and Malvo. A killing in connection with a federal crime can bring the death penalty.

Extortion and threats apparently come into play because police found a note from the snipers outside an Ashland, Va., restaurant after the penultimate shooting. The note demanded $10 million to stop the violence.

Because Muhammad and Malvo are in federal custody, the decision on where they are tried will rest with Ashcroft. Muhammad is being held on a federal weapons charge and Malvo on a material witness warrant.

"Nothing is decided," a Justice Department official said last night, cautioning that if federal charges were filed today, those charges would not necessarily be tried first.

"The filing of charges, if that is done, will not answer the question of who would go first," another official said.

Several elements are likely to enter into the debate in the next few days as authorities decide where the best case can be made. Many of the prosecutors agree that the jurisdiction with the strongest evidence should go first because it is crucial to win a capital conviction the first time out.

Many of the factors seem to favor Virginia, sources said, including the fact that neither Maryland nor federal law allows the execution of juveniles such as Malvo. In addition, although Maryland and Virginia have a so-called triggerman rule requiring prosecutors to prove who fired the fatal shot, Virginia has a way around it with the terrorism law.

The question of who pulled the trigger in each shooting is an important one for prosecutors, who have to present either direct or circumstantial evidence to juries about that fact. Several sources said yesterday that so far, there is no direct evidence linking the men to specific shootings.

But the new Virginia law -- enacted July 1 -- allows prosecutors to seek the death penalty against anyone who was part of a terrorist act.

"What makes it terrorism is the extortion, the widespread nature of it and the fact that people were put in terrible fear," said Prince William Assistant Commonwealth's Attorney James A. Willett, who has successfully prosecuted six death penalty cases. "With the new statute, there won't be a need to show which one was the triggerman. We'll all be walking on new ground."

Hanover County Commonwealth's Attorney Kirby H. Porter, who yesterday announced grand jury indictments related to the Oct. 19 Ashland shooting, said he decided to charge the pair under the statute because it represented a perfect test case.

The terrorism law passed overwhelmingly during this year's General Assembly session. Virginia Attorney General Jerry W. Kilgore said crimes such as the sniper shootings were not specifically considered during the debate last winter.

"Certainly, we were thinking of Osama bin Laden," Kilgore said last night. But he said prosecutors "could use this terrorism law as a backup if you will, another option in their arsenal. They certainly plagued an entire community. It locked that community into that situation of fear."

State Sen. Kenneth W. Stolle (R-Virginia Beach), who co-sponsored the legislation, echoed Kilgore's enthusiasm for using the sniper prosecutions as a way to test the terrorism law. Stolle recalled discussions during the drafting of the legislation that centered on the idea that an assailant might write notes to the police or the public intended to incite terror. Hearing of the notes left by the sniper -- one of which said, "Your children are not safe anywhere at any time" -- made him think of the law's applicability, he said.

"This is exactly what we discussed," he said. "The note in the Hanover case could be used for all of the other cases as well."

Kilgore pointed out one danger in using the law: It is untested. Courts have not had an opportunity to say whether the definition of a terrorist act is too broad or whether the many pieces of the legislation meet constitutional muster.

"That's certainly a danger," Kilgore said. "That's why prosecutors, when they can show the shooter, will use the traditional capital murder statutes."

Prosecutors in Prince William and Spotsylvania took that tack as well, filing additional capital murder charges under a more commonly used Virginia provision making it a capital offense to kill twice within a three-year period. But to get the death penalty under that law, prosecutors would have to prove who pulled the trigger.

Muhammad was charged in separate indictments in Virginia with four counts of capital murder and several weapons and conspiracy charges. Malvo was charged identically under the state's juvenile code, and prosecutors said they would seek to try him in adult court.

Virginia prosecutors spared no time in getting indictments because of a state law that would bar such cases from going to court if federal charges came first. Fairfax County did not seek indictments yesterday -- the only Virginia jurisdiction with a fatal sniper shooting that did not.

Fairfax County Commonwealth's Attorney Robert F. Horan Jr. said he did not join other Virginia prosecutors in pursuing indictments because not all the evidence has been processed.

"I'm going to wait until I see the forensic reports," Horan said, adding that he has seen no evidence indicating who fired the gun in any of the incidents. "It's the purest kind of speculation to say which did which," he said. "They were both in the car at the time of the arrest. That's all we know for sure."

Other prosecutors said they went forward with the expectation of having plenty of time to investigate.

"We can't do anything as long as they're over in Maryland," one prosecutor said. ". . . They know about the death penalty in Virginia. They know where the hammer is."

Staff writers Christian Davenport, Maria Glod, Lyndsey Layton, Brooke A. Masters, Michael D. Shear and Katherine Shaver contributed to this report.

Hanover County Commonwealth's Attorney Kirby H. Porter.