The D.C. Police Department, which requires officers to carry their revolvers at all times, is liable for damages if off-duty officers use those weapons improperly, a D.C. Court of Appeals panel said yesterday.

The panel, in a 2-to-1 ruling, said a D.C. Superior Court judge erred when he overturned a 1979 jury verdict of $180,000 against the city after an officer used his service revolver to kill his father-in-law and wound his estranged wife and young son in 1974.

Appeals court Judge John M. Ferren said in yesterday's opinion that the city had a "general duty, owed to the public at large, to use reasonable care in supervising and controlling police officers and their service revolvers."

In a brief dissent, retired Judge George R. Gallagher, who was an active member of the appeals court when the case was argued nearly two years ago, said the majority decision "has the potential to bring about undeserved verdicts against the city with great financial loss to what is apparently regarded as the 'deep pockets' of the District of Columbia."

Gallagher said the liability placed on the city by the decision will "invite dangerous abuse," and that employers should not be liable for crimes committed by employes in their private lives.

City officials yesterday said they could not immediately assess the impact of the decision, and that they did not know whether the panel's decision would be appealed to the full appeals court.

The police officer in the case, John Henry Morgan Jr., was convicted in 1975 of first-degree murder in the shooting death of his father-in-law, Elton Pinkney. Morgan's wife, Garnett P. Morgan, and other surviving family members sued the city for damages.

The family contended that because the police department knew Morgan had threatened his wife before he walked into his father-in-law's home in Southeast Washington and began firing his gun, officials should have taken steps to prevent the incident. The jury agreed and awarded the family $180,000.

Shortly afterward D.C. Superior Court Judge Fred B. Ugast overturned the verdict, ruling that the officer's family had failed to show what legal responsibility the city had for Morgan's actions.

The family appealed, and yesterday the panel reinstated the jury's verdict. The majority said the jurors acted reasonably and pointed out that the department failed to investigate Garnett Morgan's complaint that her husband threatened her, failed to institute disciplinary proceedings and failed to disarm the officer during those proceedings.

Ferren said the city's responsibility was the same as it would be in any negligence case, namely, to exercise "reasonable care under the circumstances."

Ferren, citing earlier court rulings, said the goverment had a duty to "minimize the risk of injury to members of the public that is presented by its policy of requiring officers to carry service revolvers at all times" and that the city as a "corporate entity" had a duty to "supervise, train and control its police officers."