A 20-year-old Burke man who had been charged with murder in the stabbing of another youth at the Pentagon Metro station last summer pleaded guilty to a lesser charge yesterday, sparking complaints from the victim's father that the plea bargaining arrangement was too lenient.

As a result of an agreement between defense lawyers and Arlington prosecutors, Kevin J. Durgin pleaded guilty to voluntary manslaughter in the death of Frank Clarke Finnell III, 19, of Alexandria. Finnell was killed in a scuffle following the fireworks on the Mall last July 4.

His death was the first and only homicide on Metro since the subway system opened six years ago, according to transit authorities.

Under Virginia law, Durgin could serve up to 10 years in prison, or could be granted parole and released. Sentencing for Durgin, who is being held without bond in Arlington County jail, was set for Jan. 27.

"Justice, you call that justice?" said the victim's father, Frank Clarke Finnell Jr. of Montgomery County, after hearing Arlington Chief Circuit Court Judge William L. Winston accept Durgin's guilty plea. "My son is dead, and there's a very good chance that this kid is going to walk out of here on probation."

Kenneth E. Melson, Arlington's deputy commonwealth attorney, defended the plea bargaining agreement, saying that he did not believe it would have been wise to press prosecution of first- or second-degree murder given the facts of the case and the history of Arlington jury verdicts in similar cases. "I can understand why the father feels that way," said Melson. "And from an emotional point of view I feel the same way he does. I feel the sentence for voluntary manslaughter is too low."

Durgin's attorneys also defended the agreement. "Based on the facts, it's justice," said Cheryl A. Wheeler.

According to an account of the incident presented in court yesterday, Finnell was walking across the Mall to a Metro stop with seven friends when Durgin, a stranger, stopped them and attempted to "pick up" two girls in the group. Finnell and Durgin were both intoxicated, Melson said, and a loud argument erupted in which witnesses said Finnell threatened to kill Durgin, attempted to punch him and missed, hitting one of the two girls.

Friends separated the two and Finnell boarded the subway at the Smithsonian stop at Independence Avenue, Melson said. Durgin boarded the same car and hurled taunts at Finnell as they rode to Virginia, the prosecutor said. When the train stopped at the Pentagon station shortly after midnight, Melson said, a scuffle ensued and Finnell came at Durgin with his fists raised.

Durgin, a burly young man who was half a foot taller and 50 pounds heavier than Finnell, pulled out a knife with a six-inch blade and stabbed Finnell, killing him almost instantly, Melson said.