Fairfax County's top prosecutor, Robert F. Horan Jr., expressed confidence yesterday that investigators acted properly in questioning John Lee Malvo for seven hours Thursday night without a lawyer or guardian present, an interrogation in which sources say the 17-year-old took responsibility for pulling the trigger in several attacks.

Horan -- who continues to refer to Malvo only as "the juvenile" because the case against him has not been transferred to adult court -- declined to comment on what was said in that session, and he criticized unnamed law enforcement sources for leaking details.

"I've heard that the defendant's attorney is outraged, and he can't be more outraged than I am," Horan said. "The right of the American people to know is not the right of the American people to know right now."

At the same time, Horan said, "I'm satisfied that the Fairfax police followed the rules" in their dealings with Malvo, who along with John Allen Muhammad, 41, is charged in the Washington area sniper shootings and suspected in attacks in several other states.

Although Malvo's attorneys have argued strenuously that the questioning of the teenager was illegal and unethical, Horan said yesterday that any suspect, juvenile or adult, can choose whether to talk to the police.

"Hypothetically, any juvenile has the right and the ability to waive his constitutional rights, just like an adult can," Horan said. "The question is: Were those rights explained, did he understand those rights and did he waive those rights?"

Officials across the country continued to look at unsolved shootings to see whether ballistics or other evidence might link them to Muhammad and Malvo.

In Atlanta, a high-ranking law enforcement source said yesterday that a witness saw Malvo lean out of a car window and, using a handgun, kill a man who was standing outside a liquor store early Sept. 21. No charges have been filed in that case, but ballistics evidence links that attack to a handgun found in Montgomery, Ala., where police have charged Muhammad and Malvo in an attack later that day.

In Northern Virginia today, federal officials are scheduled to turn over information about their investigation to authorities in Prince William County and Fairfax, as the focus of the case continues to shift from Maryland toward the two counties where the first trials will be held.

Muhammad and Malvo were transferred Thursday afternoon from federal custody in Maryland to Virginia for prosecution after federal extortion charges against them were dropped. U.S. Attorney General John D. Ashcroft decided that Malvo would be tried first in Fairfax for the Oct. 14 slaying of Linda Franklin, 47, near a Home Depot, and that Muhammad would be sent to Prince William to stand trial for the Oct. 9 killing of Dean H. Meyers, 53, at a gas station near Manassas. Ashcroft cited Virginia law and the evidence in making the decision. Unlike Maryland, Virginia allows the state to pursue capital murder charges against juveniles.

Malvo and Muhammad are suspected in 21 shootings -- 14 of them fatal -- in Maryland, Virginia, the District, Washington state, Alabama, Georgia and Louisiana.

In Prince William and Fairfax, Muhammad and Malvo are charged with two counts each of capital murder. In each case, one count involves a provision of Virginia's standard capital punishment law that makes a killer eligible for the death penalty if he kills more than once in three years. Under that provision, the prosecutor must prove someone was the "triggerman" to obtain a death sentence.

Prosecutors also have invoked Virginia's new anti-terrorism law to charge that the men carried out the shootings to intimidate the public or influence the government. Under the terrorism statute, in effect since July, prosecutors do not have to prove who pulled the trigger.

When Malvo and Muhammad were transferred to Virginia, they were effectively left without lawyers, because the lawyers who represented them against the federal charges in Maryland had not been appointed to defend them in Virginia.

That created an opportunity for investigators to seek to question Muhammad and Malvo on Thursday night and into Friday, before they appeared Friday in Virginia courtrooms and had attorneys appointed for them.

Muhammad refused to talk in those hours, sources said, but Malvo gave investigators details of some of the attacks. Sources say Malvo said he pulled the trigger in several: the killing of Franklin at Seven Corners; the Oct. 22 death of bus driver Conrad Johnson in Aspen Hill; and the Oct. 7 wounding of a 13-year-old boy at a school in Bowie. A source said that Malvo gave conflicting statements about the shooting of Meyers near Manassas -- at one point saying he pulled the trigger and at another point saying he did not.

Malvo's attorneys say they will try to have his statements ruled inadmissible in court, although prosecutors and some lawyers not involved in the case believe that will be difficult if police can show they followed legal procedures.

"We do have very strong issues with Fairfax County police interrogating the guy, knowing that by moving him [to Virginia] he would lose any possible representation," said Thomas B. Walsh, one of Malvo's attorneys in Virginia.

Todd G. Petit, a Fairfax lawyer who was appointed Malvo's guardian last week, met with Malvo yesterday and said his client "obviously is concerned. He's trying to be optimistic. But this is a very difficult position for a 17-year-old boy to be in."

After being appointed Malvo's guardian Thursday afternoon, Petit, a former public defender, went to Fairfax police headquarters and tried to stop the questioning. Fairfax police took his card and sent him away.

Petit, as the legal equivalent of Malvo's parent, said that "whether a parent gives permission for the questioning is a factor in whether a statement is admissible." Petit added, "I also find it concerning that, knowing I was there, the police department continued to question this 17-year-old boy for seven hours."

Martin Lester, the Fairfax public defender, said that moving Malvo to Virginia and leaving him without a lawyer was "a blatant and unjust manipulation of the rules." But, he said, it will be difficult for defense lawyers to have Malvo's statements ruled inadmissible if Malvo didn't ask for a lawyer during the questioning.

Muhammad's attorney, Peter D. Greenspun, said he had an "extended visit" with Muhammad at the jail in Prince William yesterday, but he wouldn't comment further on the case.

He did express dismay that details of Malvo's statements to investigators had been leaked to reporters.

"This is not just a leak," Greenspun said. "It is the opening of a floodgate by police of unchallenged, inaccurate and likely illegally obtained statements affirmatively put out in the media for the purpose of ensuring public opinion at the outset and to taint the jury pools. Law enforcement knows better and should be embarrassed by this outrageous conduct."

In Atlanta, police continue to investigate the Sept. 21 slaying of Million A. Woldemariam, 41, who was shot at 12:15 a.m. outside a liquor store.

The witness told police that a man shot from the window of a Chevrolet Caprice. The witness, who later identified Malvo as the shooter, said that the car drove off slowly and that there was no attempt to rob the man. Prosecutors in Atlanta are considering charges in the case.

Muhammad and Malvo are charged with killing one woman and wounding another in Montgomery, Ala., later that day.

One of the Alabama victims, Claudine Parker, 52, was slain with the Bushmaster rifle that Muhammad and Malvo allegedly used later in the Washington area sniper attacks, according to ballistics tests cited by investigators.

Police said the other Alabama victim, who was wounded, may have been shot with a .22-caliber handgun found along the route taken by Muhammad as he ran from police. Atlanta police officials said ballistics tests have confirmed that the nickel-plated revolver was used to kill Woldemariam.

Staff writers Sari Horwitz and Josh White contributed to this report.