The only teenager charged as an adult in this year's string of juvenile joyriding deaths pleaded guilty yesterday to killing a 21-year-old man last month in Southeast Washington.

Looking anxious and speaking in a reluctant whisper, Andrew Lofty, 16, admitted being behind the wheel of the stolen minivan that plowed into Terry Andrew Weaver on July 2 on G Street SE.

It was the first conviction of a driver in the four recent deaths linked to juvenile joyriders, many of whom operate stolen cars.

Charged with second-degree murder, Lofty pleaded guilty in D.C. Superior Court to the lesser charge of involuntary manslaughter. The agreement did not seem to make it any easier for him to address the court and acknowledge his guilt.

More than once, Judge Robert I. Richter had to repeat a question as he queried the defendant.

"How do you wish to plead, guilty or not guilty?" Richter asked. Lofty, dressed in an orange jail jumpsuit and standing next to his attorney, James E. Williams, said nothing. "Guilty, or not guilty?" Richter asked again.

"Guilty," Lofty murmured.

Unlike a charge of murder or voluntary manslaughter, which generally requires that the defendant had a specific intent to kill, involuntary manslaughter requires evidence only that the defendant should have known the potentially fatal risks of his or her actions.

Lofty was traveling about 15 mph over the 25 mph limit and was in the oncoming traffic lane when he collided with Weaver's motorcycle. Five other youths were in the minivan, and all have been charged as juveniles; two have pleaded responsible to various charges, and the other three are awaiting trial.

The maximum sentence for involuntary manslaughter is 30 years, and the maximum for unauthorized use of a vehicle -- the other charge Lofty pleaded guilty to -- is five years.

By pleading guilty just a month after he was charged and before he was indicted by a grand jury, Lofty has probably earned himself a measure of leniency when he is sentenced Oct. 15.

Defense attorneys and the prosecutor both said the plea was the right outcome.

"There was really no dispute about the facts," Williams said outside the courtroom. "Involuntary manslaughter would have been a good resolution after a trial."

Assistant U.S. Attorney Jay Balacek said the deal was "appropriate."

In the corridors outside the courtroom and on the sidewalk outside the courthouse, Lofty's mother, Vivian Lofty, and his uncle, Vernon Knight-Bey, expressed sympathy for Weaver's family.

"We feel sorry for the family of the young man my nephew killed," Knight-Bey said, calling it an accident.

Vivian Lofty said that she had tried to keep her son in line and out of trouble but that he was defiant. "I talked to my son plenty of times, and he didn't listen," she said.

Now, she said, she is resigned to the fate of Weaver and the fate of her son. "I can't bring that person back," she said, "but my son is going to pay the price."