Richard Lee Earman, acquitted of murdering an Arlington couple in 1977 in one of Northern Virginia's most celebrated murder cases, pleaded guilty yesterday to a separate, lesser charge of conspiring to murder the couple.

His plea was the latest turn in a bizarre case that has been a source of friction between police and prosecutors in Arlington and has embroiled Virginia's attorney general in a running feud with the Arlington common-wealth's attorney, William S. Burroughs.

Earman, a 36-year-old former real estate salesman, offered the plea yesterday afternoon, telling a reporter he had been hounded by a Washington woman who wants to write a book with him about the crime. "That tough, old broad just kept on me until I cracked," Earman said of writer H. Kaya Ploss, who is collaborating on the book with Earman.

Burroughs said he and Fairfax County prosecutors have agreed to drop various felony charges against Earman in return for his plea and Earman's promise to testify against Joseph N. Martin, who also had been charged with murder previously in the 1977 killings.

Martin was arrested Tuesday in Las Vegas and charged with conspiracy to murder the couple, the same charge to which Earman pleaded guilty yesterday.

Burroughs said yesterday that he expects Earman will receive a 10-year prison sentence on the conspiracy charge when he is sentenced, probably after Martin's trial.

Martin, 28, a former salesman for New York Life Insurance Co., was brought before an Arlington judge yesterday, but his preliminary hearing was postponed until March 21. He was identified at Earman's 1977 murder trial as the person who sold a $56,000 life insurance policy on Alan Foreman, 26, several months before Foreman and his fiance Donna Shoemaker, 25, were found shot to death in the garage of Foreman's North Arlington home.

Burroughs dropped the murder charge against Martin in the middle of the eitht-day trial in 1977, citing "new evidence" in the case that the prosecutor said indicated Martin was innocent.

"When I dropped the charges in 1977," Burroughs said in an interview yesterday, "and requested that police cotinue their investigation, I always knew that, if new evidence was developed, the case against Martin could be reopened, and that is what happened."

Burroughs refused yesterday to discuss what new evidence led to Martin's arrest and Earman, who is free on $2,000 bond, also declined to discuss who killed the couple. "That will come out in Martin's trial," Earman said.

"Nobody likes to go to jail, least of all me," said Earman. "But if I didn't do time, the police would just keep after me. I'm relieved it's over."

Ploss, who was in the Arlington Circuit Court room when Earman pleaded guilty, agreed that Arman had done the right thing. "We had many serious talks," she said. "Lee knew he had to do this."

Under Virginia law, Earman, who describes himself as a self-employed tennis instructor, could be eligible for parole in aboot three years if he receives the 10-year sentence that Burroughs mentioned.

His 15 minute court hearing before Judge Charles S. Russell was attended by Foreman's mother, Sally Dixon, who wept quietly as Earman pleaded guilty and later smiled at Burroughs as she left the courtroom.

Earman's appearance in the hushed courtroom capped a day of hectic closed-door meetings between Earman, his attorney LeRoy E. Batchelor, Burroughs and the judge as they worked out details of the plea agreement.

Last year, following complaints by Arlington detectives and Ploss that Burroughs had hampered the murder investigation and refused to prosecute Martin, Virginia Attorney General J. Marshall Coleman ordered a state police investigation of Burroughs' conduct in the case.

After a three-month investigation, Coleman, a Republican, announced that he was clearing Burroughs, a Democrat, of any criminal misconduct in the case. But that has not ended Burrough's anger over the state investigation, and he has repeatedly called for a new, separate investigation into why Coleman ordered the probe.

Martin, who was freed on $2,500 bond yesterday, had been arrested in Las Vegas where he worked as a sales manager for a photocopy firm.

"I can't believe it," Martin said when contacted last night. He declined further comment.

Martin had said last year that he moved to Las Vegas to escape what he saw as "harassment" from police that he said continued after the charges against him had been dropped.