A District man pleaded guilty yesterday to second-degree murder in last year's suffocation slaying of a 28-year-old Army captain, saying he was very sorry that a burglary cost a woman her life.

Joseph D. Washington, 19, in a voice hushed with emotion, told D.C. Superior Court Judge Fred L. McIntyre that he was guilty of killing Camille DeRose Chapman during a burglary of her Northwest home on Feb. 27, 1984.

Washington, pleading to reduced charges before the scheduled start of his trial, told the judge he had made a "big mistake." He said, "I'm very sorry that a life was taken in the course of a burglary."

Hazel Chapman, the slain woman's mother, sat in the fourth row of the courtroom and fought tears as the prosecutor outlined the burglary and attack that led to Chapman's death by suffocation.

Chapman's body, her legs bound and a bag over her head, was found the next day after her family couldn't reach her by phone.

"When I heard the taps and they lowered her body into the ground I felt a part of me was gone forever," Hazel Chapman, a teacher, said later. "It is a part of me I don't feel I will ever regain."

Washington pleaded guilty to one count of second-degree murder while armed, which carries a maximum life penalty, and a first-degree burglary charge, which carries a maximum of 30 years. In exchange for the plea, the government agreed to dismiss a felony murder charge and other charges, including rape and armed robbery.

Washington, who was 17 at the time of the killing, could be sentenced under the old federal Youth Corrections Act, which would make him eligible for an indeterminate sentence. Had he been convicted of felony murder, Washington would have faced a minimum sentence of 20 years. McIntyre scheduled sentencing for Sept. 27.

Washington's plea came moments before McIntyre was scheduled to rule on whether to admit as evidence Washington's statement to police that he was in Chapman's house at 5403 Seventh St. NW the day she was killed and watched as she tried to fight off other attackers. After Washington entered his guilty plea, McIntyre said he would have permitted introduction of the statements.

In a videotaped statement recorded one month after the murder, Washington told police that he and four other men broke into Chapman's house through the basement on Feb. 27. When he reached Chapman's second floor bedroom, Washington said, some of the other men already had raped her.

Chapman, Washington said on the tape, tried to fight off her assailants but they wrapped a cord around her legs and tied them to a dresser. At that point, Washington said he was "scared" and decided to leave the house, according to the tape. Later that day, Washington said on the tape, he and some of his companions returned to the home and took the brass bed, a mattress, some sheets and towels.

No other arrests have been made in the killing.

Public defender Mary Lou Soller had argued that her client was pressured into making his statements because he had little experience with police procedures, was only 17 at the time and had been drinking heavily the previous night. Prosecutor Mike Hannon countered that police had exceeded their obligations in protecting his rights.

After Washington's plea yesterday, Chapman's mother, brother and other relatives talked about how excited "De," as they called her, was about her move to Washington and the recent purchase of her first home after spending several years living on Army posts.

"I told her to go to the police department and check the crime rate," Hazel Chapman said, recalling how her 98-pound daughter later told her the police said the neighborhood had a low crime rate.

After Chapman's home had been broken into again, her mother said she urged her daughter to move or get a dog. When it was broken into the third time she told her daughter to change the locks.

"The first time it was broken into, De thought it was a bunch of kids furnishing a house because the things they took -- frozen food from her freezer -- were so ridiculous," said her cousin, June Daugherty. "But when she was broken into the second time she told me, 'If I don't go back in this time I will never be able to go back in it and stay.' "