The Prince George's County state's attorney's office will investigate all serious shootings by law enforcement officers in the county and present the cases to a grand jury under a new policy outlined yesterday by the county's top prosecutor.

State's Attorney Alex Williams, who promised in his inaugural speech in January that he would implement a policy for reviewing police shootings, said the new guidelines also would extend in some cases to allegations of police brutality.

For years the county has grappled with the police force's reputation, and the 1970s produced a steady stream of brutality complaints, especially from black county residents.

The perception among many members of the black community that the department often used excessive force came about during a time when the department remained more than 95 percent white while the county's black population was doubling. The 900-member department is now 25 percent black, while the county population is more than 45 percent black.

The department has made other changes to combat the negative perception, including hiring more black officers and adding sensitivity training for new and current officers to make them more aware of cultural differences.

Williams' election was in some measure a repudiation of the policies of incumbent Arthur A. Marshall Jr., who during 24 years as state's attorney did not review cases if police investigations ruled that shootings were justified.

After seven months in office, Williams was beginning to face questions from black supporters who expected him to act more quickly on his inaugural promise to deal with police brutality.

Williams raised some eyebrows in March when he said that the county police department had made progress and no longer deserved its reputation for police brutality.

Referring to his new policy yesterday, Williams said: "I think a clear, consistent policy helps the community. And quick action by our office also will help to relieve a lot of anxiety for officers involved."

The new policy will apply to shootings by any law enforcement officer in the county, including Prince George's and municipal officers, state police and sheriff's deputies, Williams said.

Currently, county police investigate any shooting by one of their own officers or by officers from many of the independent jurisdictions in the county. Larger municipalities such as Greenbelt and Hyattsville and the state police conduct their own investigations.

In all cases of police shootings, law enforcement agencies send results of their investigations to the state's attorney's office for review. But not all of those cases are presented to a grand jury.

Williams said he has sent copies of his policy to county law enforcement agencies for review. The heads of the county's largest two law enforcement departments -- Police Chief Michael Flaherty and Sheriff James Aluisi -- said it would be inappropriate to comment on the policy because they had not seen it.

Williams said that state's attorneys in Montgomery County and Baltimore County have similar guidelines on shootings by police officers.

Only one case of a police shooting has been presented to the grand jury since Williams took office in January. In that case, where a Cottage City officer fatally shot a man, the grand jury declined to indict the officer.

Williams said his office also will look into allegations of excessive force from people whose complaints are not investigated by police agencies within 90 days from the filing of the complaint or if the alleged victim is not satisfied with the outcome of the police investigation.

County police currently investigate all complaints against officers within 90 days, said Carol Landrum, a department spokeswoman. In the last three years, she said, there has not been a complaint that was not investigated within 90 days.

If the complaint is unfounded, she said, the department notifies the alleged victim and the officer of the investigation's results. If there is some basis for the allegations, Landrum said, the officer and victim are notified and a police trial board hearing is scheduled.

Williams said his office will direct anyone with an allegation of excessive force to the law enforcement agency or the county Human Relations Commission. "If they are not satisfied with the results, or if nothing happens within 90 days," he said, "then we will explore criminal prosecution."

Williams said he does not anticipate a flood of complaints alleging police brutality because a majority of the allegations have no merit.

From 1979 to 1986, according to figures provided by the county police and the Human Relations Commission, 269 allegations of excessive force were made against county police. Eight of the complaints have been upheld.