Almost two years after a lone gunman killed two FBI agents and a D.C. police sergeant inside the District's police headquarters, three members of the killer's "crew" pleaded guilty yesterday to participating in a racketeering conspiracy.

Although the criminal charges covered by the pleas had no legal connection to the police headquarters killings, U.S. Attorney Eric H. Holder Jr. said they "stand as a testament" to the commitment of investigators who gathered evidence against the drug crew. He called it "a fitting tribute" to their colleagues who were slain.

As part of their plea bargains with the government, two members of the First and Kennedy Street Crew -- Kobi Mowatt, 25, and Jermaine Graves, 24 -- each will spend 35 years in prison for his role as a key leader of the drug crew that terrorized that Northwest neighborhood since at least 1988. A third defendant, Marcel D. Washington, 23, agreed to a prison term of more than 16 1/2 years for his role in the group.

The three defendants were part of a case originally brought against eight members of the gang a year after Bennie Lee Lawson walked into D.C. police headquarters Nov. 23, 1994, and shot to death Sgt. Henry Joseph Daley, 51, and FBI agents Michael John Miller, 41, and Martha Dixon Martinez, 35, and seriously wounded FBI agent John David Kuchta, 31. Lawson then apparently killed himself.

Mowatt, Graves and Washington admitted to participating in a ruthless gang that killed, robbed or shot anyone who tried to infringe on its turf. In court papers, prosecutors William M. Blier and Patricia M. Haynes said the crew warred openly with rival drug dealers from Seventh and Kennedy streets NW.

Mowatt, Graves and Washington will be sentenced Jan. 7 by U.S. District Judge Royce C. Lamberth, who approved the plea bargains and the prison terms they specify. The five other defendants -- Mark E. Bundy, 23; Gregory E. Ray, 23; Jesse L. Bell, 22; Antoine E. Boyd, 24; and Dorian M. Ray, 22 -- pleaded guilty earlier and are awaiting sentencing. Of them, only Bell cooperated with authorities. Two other crew members pleaded guilty after their arrests last year and were not named in the indictment.

Had the case gone to trial, prosecutors and defense attorneys said, the jury probably would have heard gruesome details of Lawson's bloody rampage at police headquarters. David A. Sidbury, Washington's attorney, said his client decided to plead guilty because he would have faced life in prison without parole if he had gambled on a jury trial and been convicted.

"It was a tough decision," Sidbury said. "It spared a lot of people a lot of pain. We don't need to relive all of that."

During their probe of the headquarters shootings, officials learned that Lawson believed that he was going to be charged with a triple murder that he, Graves and Mowatt committed in October 1994. He had been told as much when police interviewed him about the slayings not long after they happened. Lawson was told that police were analyzing blood and vomit found at the scene to identify one of the killers. According to court papers, Lawson had gotten sick outside the house where the three people were slain.

Lawson, who had been raped in prison while serving time on a firearm conviction, also had vowed that he would never again be locked up. Authorities speculate that his brazen attack on police headquarters also may have been an attempt to regain the respect of his friends.

When he walked into police headquarters, Lawson headed for what he thought was the police homicide unit, which was investigating the triple killings. But he walked into the wrong room, entering the offices of the "cold case" homicide squad. There, he pulled out a gun and immediately shot Daly to death. In the fierce gun battle that ensued, he killed Miller, wounded Kuchta and shot Martinez to death after he disarmed her and took her gun.