Lee Boyd Malvo became an adult in the eyes of the court yesterday when authorities unsealed an indictment charging him with capital murder, making him eligible for the death penalty.

Malvo's indictment, which came 27 days before his 18th birthday, marks the first step in his prosecution in Fairfax County Circuit Court for the Oct. 14 sniper slaying of FBI analyst Linda Franklin, 47. But the case already is influencing the national debate over whether people who kill as juveniles should be eligible for execution.

Last fall, Attorney General John D. Ashcroft said he sent Malvo to Virginia for trial so he could face the "ultimate sanction" if convicted in the October shooting spree that left 10 dead and three others wounded. Of the 38 states that have the death penalty, 22 -- including Virginia -- allow execution for juvenile crimes.

Since 1924, Virginia has executed three men who committed murder as juveniles. Another is on death row.

The grand jury charged Malvo with two counts of capital murder -- murder of more than one person in three years and murder as an act of terrorism -- in connection with Franklin's slaying outside a Seven Corners Home Depot. Malvo also was indicted on a firearms charge. The grand jury charged Malvo under the name Lee Boyd Malvo, which authorities said is his legal name, rather than John Lee Malvo, which had been used in previous legal proceedings.

Fairfax County Circuit Judge Jane Marum Roush, whose high-profile cases included a 2001 capital murder prosecution that ended in a plea, was appointed yesterday to Malvo's case. Prosecutors said Malvo could go to trial as soon as this summer, but defense attorneys said they will need considerable time to prepare for the complex case and predicted a later trial date.

Legal experts said Malvo's case may interrupt what had become a growing sentiment against executing juvenile defendants. In 1999, Montana banned the death penalty for people who committed capital crimes while younger than 18, and Indiana followed suit last year.

In October, four U.S. Supreme Court justices said they opposed executing defendants who committed capital crimes at age 16 or 17, calling such executions "a relic of the past [that] is inconsistent with evolving standards of decency in a civilized society." The opinion, written by Justice John Paul Stevens and joined by Justices David H. Souter, Ruth Bader Ginsburg and Stephen G. Breyer, dissented from the majority's refusal to consider whether such executions were "cruel and unusual."

The Supreme Court seemed poised to outlaw such executions, and "then the sniper case hit," said New York Law School professor Robert Blecker, who argues that juveniles should be eligible for the death penalty.

"It exploded any possibility that [the court] could claim a national consensus against executing anyone who committed crimes when they were under 18," Blecker said.

Victor L. Streib, a law professor at Ohio Northern University who studies the death penalty, said he believes the Supreme Court eventually will ban the execution of juvenile offenders, just as the court recently barred the death penalty for the mentally retarded.

"The death penalty for juvenile offenders has been fading fast for some time, and it's possible Malvo's case will cause a little blip," Streib said. "But ultimately, I think it's fading fast."

Legal experts said they expect both supporters and opponents of capital punishment to try to make points with the Malvo case.

"It would be a convenient case for those who support leaving the law the way it is," said Richard C. Dieter, who heads the District-based Death Penalty Information Center.

Malvo and John Allen Muhammad, 42, are suspected in the Washington area sniper shootings and nine other shootings around the country.

During Malvo's preliminary hearing last week, Fairfax County Commonwealth's Attorney Robert F. Horan Jr. said the pair taunted police in letters and phone calls and carried out the shootings in an attempt to extort $10 million from the government. Muhammad is facing trial in Prince William County on capital murder charges in the Oct. 9 slaying of Dean Harold Meyers, 53, at a Prince William County gas station.

Dieter said Malvo's case can be cited by those who believe that juvenile offenders should not be executed because they "aren't as intellectually mature, they are often led by older compatriots." Dieter said evidence and accounts by people who know the sniper suspects suggest that Malvo was strongly influenced by Muhammad.

"As soon as you think of Malvo, you think of Mr. Muhammad, too," Dieter said. "In a way, this underscores the problem of juveniles and the death penalty."

Joshua Marquis, a prosecutor in Oregon and member of the National District Attorneys Association, declined to discuss Malvo's case specifically, but he noted that prosecutors rarely seek the death penalty in juvenile cases.

"The tiny, infinitesimal number of teenagers who are sentenced to death in the U.S. commit crimes that are adult crimes, that are so horrific that no child would commit them. That's why we treat children differently than adults," Marquis said.

According to the Death Penalty Information Center, 21 people have been executed for juvenile crimes since the reinstatement of capital punishment in 1976.

In recent years, Virginia has executed three men who were minors when they killed. In October 1998, Dwayne Allen Wright, who was 17 when he fatally shot an Annandale mother of three, died by lethal injection and became the first Virginia inmate since 1924 to be executed for a crime committed by a minor. The killing was part of a five-day rampage during which Wright shot two other people, one fatally, in Prince George's County. Horan successfully argued that case.

Two other Virginia men who committed murder as minors were executed within three days of each other in January 2000.

Lee Boyd Malvo's case is fueling a national debate about executing defendants for crimes committed as juveniles.