A federal judge yesterday ordered Prince George's County police officials to turn over thousands of files on investigations of police brutality and other complaints made by citizens against county officers.

The order arose from a $12 million lawsuit filed by the wife of a District of Columbia fireman who was shot and killed by a county policeman in 1974 in what the suit claims was excessive deadly force.

Lawyers said the request for documents for as far back as 10 years before the shooting was necessary to show a pattern of brutality by county officers, which has "never properly been investigated by the department."

The action by U.S. District Court Judge Herbert F. Murray in Baltimore may for the first time open to public scrutiny the records of the police department's internal affairs unit, which investigates citizen complaints against police officers. The county police department has been criticized by some groups for alleged brutality.

County attorney Bob Ostrum said the county would study whether it could appeal the order.

"It's volumes of material," said Osterum, "possibly revealing investigative techniques, informants' names and much information that should remain confidential. Obviously you must have confidential files to run a police department."

The suit was filed over the fatal 1974 shooting of District fireman Oris D. Townsend in his Seat Pleasant bedroom. The officer involved was William R. Atkins, who is no longer on the force.

Murray ordered that the documents be sealed until they could be examined by county police officials and, if necessary, by himself in his chambers.