Robert Lee Williams, accused of killing seven persons in August when his car plowed into a Southeast Washington bus stop, pleaded guilty yesterday to lesser charges of manslaughter, just hours before his criminal trial was set to begin at D.C. Superior Court.

In a voice so hushed it was barely audible, Williams told the judge he had used heroin "roughly 20 to 25 minutes before" the accident and also had drank "two glasses of champagne . . . , one beer and a small shot of Hennessy a cognac in Coke" before the crash that has been termed the worst in D.C. history.

"At the time, I wasn't aware that I had collided into anything . . . ," Williams said softly. "I must have passed out for a brief second or so behind the wheel of the car . . . . "

Charron McKethean, who suffered serious injuries and whose 6-month-old daughter and best friend were killed that day, sat in the courtroom's second row, trembling slightly at times and staring steadfastly at Williams. "This is still not going to bring my baby back," she said later, sobbing as she talked of her daughter, Charquita. "I'm glad it's over with . . . but I still feel he didn't pay the price."

Williams, 42, pleaded guilty to two counts of manslaughter while armed -- each of which carries a maximum life penalty -- five counts of manslaughter and a traffic charge of driving while intoxicated. At the time of accident, Aug. 25, Williams had been on parole for about six weeks from prison in Virginia, where he had served part of a 20-year sentence for bank robbery.

In exchange for the plea agreement, the government agreed to dismiss seven counts of second-degree murder and two counts of assault with a dangerous weapon when he is sentenced June 28.

U.S. Attorney Joseph E. diGenova said Williams faces a maximum penalty of 55 years to life. "Because of his age, that's the rest of his natural life," said diGenova, "which is the maximum we can get in the District of Columbia." Had Williams gone to trial on the murder charges, a maximum penalty on each charge would have been a life sentence, diGenova said.

Assistant U.S. Attorney Charles L. Hall, who was prosecuting the case, said the defense offered the plea. He said prosecutors agreed to accept it, in part, because "there are always things that can happen at trial that you don't expect . . . and that can be adverse. If you can work out a satisfactory plea you should go in that direction."

The hearing before Superior Court Judge Eugene N. Hamilton was over in less than an hour.

McKethean said she remembers leaving her home on L Street SE the day of the accident with her daughter; her best friend, Linda Taylor, and Taylor's fiance, Willie Calliham Jr., on an outing to buy the infant, called "Quita" by the family, a dress for her christening the next day. They waited with some other friends, Theodore and Sandra Chrisp and their three children, at the bus stop in the 200 block of M Street SE, where the sidewalk runs along the brick wall of the Washington Navy Yard.

"A bus passed us," McKethean recalled. "It was too crowded, and we didn't get on . . . . I happened to look down the street. I said, 'Willie, look at that car.' It was on the opposite side of the street coming fast . . . driving zigzag, 60 or 70 miles an hour."

McKethean remembers seeing the car hit the median strip. "That was it," McKethean said yesterday. "There wasn't any place to run."

McKethean said she next recalls being in the hospital. "All I can remember is asking for my baby. My older sister came in and said she had died. I asked 'what about Linda?' and she told me she was dead, too."

The Chrisp family, including a 2-week-old girl, was also killed.

Yesterday in court, the prosecutor said Williams had been traveling the wrong way on M Street at speeds of 50 to 80 mph -- so fast that "three hubcaps came off and spun into the street." He appeared in control of the car until he tried to cross onto the proper side, hit the median strip and "careened up on the sidewalk."

The injured and the families of the dead have filed a $27 million damage suit against Williams, Metro and the District, charging them with negligence, according to their attorney, Dean Swartz.

Yesterday, McKethean and her parents, and Linda Taylor's mother said they wished the case had gone to trial. "I feel as though if he had heard some testimony of what really happened, it might be something for him to deal with in jail," said Rose McKethean. "He should be aware of what he has done . . . what he is still doing to the one's that are living because it is still tearing us up."