WASHINGTON — Almost two decades after two men terrorized the Washington region in the fall of 2002 in a series of deadly sniper attacks, the Supreme Court considered on Wednesday whether one of them, Lee Malvo, may challenge his sentences of life in prison without the possibility of parole.

Mr. Malvo was 17 when he and John Allen Muhammad killed 10 people in sniper attacks in Virginia, Maryland and the District of Columbia. Mr. Muhammad was sentenced to death, and he was executed in 2009.

Mr. Malvo, now 34, was sentenced to life in prison by a judge in Virginia in 2004, before a series of Supreme Court decisions that limited harsh punishments for juvenile offenders. The questions for the justices in the case, Mathena v. Malvo, No. 18-217, were whether and how those decisions applied to Mr. Malvo.

A ruling from the Supreme Court in Mr. Malvo’s favor is unlikely to benefit him as a practical matter. He has also been sentenced to life without parole in Maryland after pleading guilty to six murders there and is challenging those sentences in a separate proceeding. In addition, he and Mr. Muhammad are suspected of killings in Alabama, Arizona, Louisiana and Washington State, and he could be charged with murder in those states. And a new sentencing in Virginia could reimpose a sentence of life without parole.