A D.C. judge sentenced a 19-year-old man yesterday to nine years in prison for the murder of a 28-year-old Army captain, telling him he had participated in a "very heinous crime," but that a longer sentence would be "destructive."

There is a need to "do justice to everybody involved," D.C. Superior Court Judge Fred L. McIntyre told the defendant, Joseph D. Washington, who was 17 at the time of the murder. "But I haven't given you a hopeless sentence, Mr. Washington. I hope you can do what is right" after being released.

Washington pleaded guilty in July to second-degree murder while armed and burglary in the slaying Feb. 27, 1984, of Camille DeRose Chapman at her home at 5403 Seventh St. NW, which was broken into three times in the month before her death.

Washington told the judge that he "was very remorseful for what happened" but that he "didn't participate in any way in Miss Chapman's death."

Washington, who lived in the neighborhood, has maintained throughout the two-year investigation that he was involved in only the burglary of Chapman's home and did not participate in her attack. Under District law, however, a person who commits a felony that leads to a death can be charged with felony murder.

Prosecutor Wallace H. Kleindienst said that a group of young men, including Washington, entered Chapman's house to burglarize it and that someone "jumped her, raped her; they tied her up . . . like a caterpillar in a cocoon and put a bag over her face . . . suffocating her with a plastic death mask."

Later that day, Kleindienst said, Washington and another man indicted in the murder, Gary Darby, returned to the house and stole "the mattress out from under" Chapman's body. Darby, Chapman's next-door neighbor, is scheduled to be tried next month on first-degree murder charges.