A 22-year-old Haymarket man pleaded guilty yesterday to second-degree murder, telling a judge that he helped friends kill a respected Loudoun County scientist with a sword.

Michael Paul Pfohl's plea in Loudoun County Circuit Court comes a little more than a year after Robert Schwartz, 57, was slashed and stabbed in his remote Leesburg area farmhouse. Pfohl did not wield the sword, or even enter Schwartz's home, but he admitted yesterday in court that a friend, Kyle Hulbert, planned to kill Schwartz and that he agreed to drive Hulbert to Schwartz's house.

Pfohl, who wore an orange prison jumpsuit and had his hair trimmed to just above his shoulders, politely answered questions from Judge Burke F. McCahill. At one point, McCahill asked Pfohl if he was guilty of murder.

"As much as I hate to say it, yes," Pfohl said, "and as much as it shames me to say it."

Pfohl's plea bargain spared him from a trial on charges of first-degree murder and conspiracy to commit murder. Under the agreement, Pfohl faces a maximum 21 years and four months in prison.

Loudoun County Commonwealth's Attorney Robert D. Anderson said the conviction is "appropriate to the level and extent" of Pfohl's involvement. Jensen Barber and Joseph R. Conte, Pfohl's attorneys, declined to comment.

Pfohl is among four young friends who were charged in connection with the Dec. 8, 2001, killing. The group hung out together at local Renaissance fairs and shared an interest in fantasy games and vampire lore.

Clara Jane Schwartz, 20, the scientist's youngest daughter and a former college student at James Madison University, was convicted in October of first-degree murder, conspiracy to commit murder and solicitation to commit murder for orchestrating the slaying. Prosecutors said she harbored a long-standing hatred of her father and told friends that Robert Schwartz, a respected expert in DNA research, abused her and poisoned her food.

During her October trial, prosecutors said Clara Schwartz sought out two men to kill her father and eventually persuaded one of them, Kyle Hulbert, 19, to do it.

Hulbert, who has a long history of mental illness and suffers from schizophrenia, is awaiting trial on charges of murder and conspiracy.

On a rainy Saturday night, prosecutors said, Pfohl drove his then-girlfriend, Katherine Inglis, 20, and Hulbert to the Springfield Mall to meet other friends and do some Christmas shopping. While there, prosecutors said, Pfohl told one of the friends that Hulbert had asked him for a ride and that he was "scared" to provide it.

"The defendant said he had to take Hulbert to do a job that night and that he didn't want to be an accessory to murder," Assistant Commonwealth's Attorney Thomas Mulrine said in court. "He knew that when Hulbert said he had a job to do that meant that Hulbert was going to kill someone."

Prosecutors said Pfohl, Inglis and Hulbert headed to Schwartz's farmhouse later that night with Pfohl at the wheel of his Honda. In a statement to detectives, Hulbert said he went inside alone with his two-foot sword and slashed and stabbed Schwartz after confronting him about the still-unproven abuse.

While Hulbert was inside, Pfohl tried to turn the car around but got stuck in the mud on the narrow dirt road. Detectives said they were able to track down Pfohl quickly because he gave the tow truck driver his name and phone number.

Inglis, a high school friend of Clara Schwartz's, faces a conspiracy charge in the case. In June, prosecutors dropped the murder charge against her after she agreed to testify against her friends.

A Loudoun jury has recommended that Clara Schwartz spend 48 years in prison. Her sentencing is set for next month. Hulbert's trial is set for March.

Pfohl is scheduled to be sentenced April 11. In a statement to detectives written the day of his arrest, Pfohl called the killing "a big oopsy."

"I knew what I was getting myself into even if only vaguely," Pfohl wrote. "I'm fully responsible for that."