A District man was convicted yesterday of raping and murdering his next-door neighbor, a 28-year-old Army captain, and later returning to steal the bed from under her body, in a finding issued by a judge after an unusual trial without a jury.

"This has been without exception the most difficult experience I've had in 8 1/2 years on the bench . . . , " D.C. Superior Court Judge Frederick H. Weisberg told the defendant, 25-year-old Gary E. Darby, who had asked the judge to try the case without a jury. "I cannot imagine a more difficult responsibility in both the power and obligation to decide the facts in a case such as this . . . . "

Darby, who sat placidly throughout yesterday's proceedings, is the second man to be convicted in the February 1984 murder of Camille DeRose Chapman, an Army accountant stationed at Buzzard Point.

Chapman, an accomplished musician who was proud of how she had renovated her house at 5403 Seventh St. NW, had reported a series of burglaries to police shortly before her death. Yesterday, Weisberg also convicted Darby of one of those prior break-ins, along with finding him guilty of felony murder, rape, and several other burglary and theft charges.

Hazel Chapman, the slain woman's mother and a schoolteacher, rushed out of the crowded courtroom as the judge announced his finding that Darby and others had raped and "brutally murdered" Camille Chapman by suffocating her during a burglary attempt.

Chapman's body, her legs and arms bound and a plastic bag over her head, was discovered wrapped in blankets like a "cocoon." Police found the body after her family became concerned because they could not reach her by phone.

Hazel Chapman said she had urged her daughter to consider moving after her house had been broken into twice, but recalled, "She told me, 'Mom, this is my house. I bought it and I am going to stay here.' "

Judge Weisberg told Darby yesterday that although the case was built largely on circumstantial evidence, in the end he believed the essential parts of the testimony of Joseph Washington, the government's key witness who pleaded guilty in June to second-degree murder in Chapman's death.

Washington testified that he and three others, including his lifelong friend Darby, broke into Chapman's house on the morning of Feb. 27, 1984, after Darby had asked Washington whether he "wanted to make some money."

Washington told the judge that he followed the others up the stairs and did not really see what occurred in Chapman's bedroom, but that he saw a leg on a mattress and heard a "mumbled" sound "like a hand or bag being put over" someone's face.

Washington said Darby, also known as Fuzzy, told him to go away. Later that evening after spending the day "getting stoned," Washington testified, he and Darby returned to Chapman's house and stole her freezer and the brass bed from her bedroom. Chapman's bound body was discovered in that room the next day.

In addition to Washington's account, prosecutor Wallace H. Kleindienst had argued to the judge that a stolen credit card later found in the basement of Chapman's house tied Darby to the woman's murder, as well as other items from Chapman's house that Darby gave or sold to others and that were later found by police. A neighbor testified that Darby had described the means of Chapman's death long before police told anyone how she died.

Darby did not take the stand in his own defense, but his lawyer, Frederick Douglas, tried to prove that the government's case hinged on a "liar and fabricator" and on weak circumstantial evidence.

Darby jumped up from his seat following the judge's finding. As he marched through the door leading to the cell block, he turned and grinned widely at the judge. Weisberg stared straight ahead, looking at the Chapman family as they left the courtroom, crying.