A D.C. police retirement board has denied retirement on medical disability to a homicide detective, rejecting his contention that he suffered permanently disabiling psychological problems when he was shot in a 1979 incident in which he killed a man.

Detective Ronald Washington, a 15-year veteran of the force, recovered from the gunshot wound but was placed on sick leave with pay last May after he and his psychiatrist told police officials that Washinbgton was psychologically disturbed by the incident and was unable to use a gun or return to work.

Washington was off duty and attending a friend's wedding in Northeast Washington in July 1979 when a guest became unruly and began threatening a security guard. Washington intervened and the two men exchanged shots. Washington was given a gold medal for his actions by the Greater Washington Board of Trade during a "heroes luncheon" last fall at the Hyatt Regency Hotel.

The retirement ruling, which was made March 19 but not announced by the Police and Firefighters Retirement and Relief Board, can be appealed to the D.C. Court of Appeals. An attorney handling Washington's retirement request was not available for comment yesterday, but Washington said he expected the decision to be appealed.

William R. Hairston, chairman of the retirement board, said the board heard Washington's case last September and "the decision was that he was not permanently disabled."

Washington was told in early March that he no longer would be paid administrative sick leave by the police department and would have to return to work. Police union attorney Michael Grealy, who is representing Washington in the sick-pay dispute, characterized this decision as "arbitrary" and said it also is being appealed. Washington, who has not returned to work, is now using his earned, accumulated sick leave.

His psychiatrist, Dr. James Ballard, wrote a letter to the police department on March 18 objecting to the change in leave status. Ballard's letter said Washington continued to suffer mental anguish about the shooting and was unfit for police work, attorney Grealy said.