Police chiefs know that brutality is an occupational risk of the profession because they cannot absolutely control their officers' behavior.

To prevent brutality, the best chiefs avoid any signal that it is excusable or that any group of people is a legitimate target of excessive police force. When brutality is alleged, good chiefs investigate thoroughly and objectively.When brutality is found, examples are made of those who committed it, those who failed to stop it and those who covered it up. If brutality exists at all in well-run departments, it is the deep, dark secret of outlaw officers.

There is no secretiveness in the Rodney G. King videotape or in the half-joking computer conversations that followed it. Instead, we see officers who had to be confident that their colleagues would remain silent and that their department would reject any citizen's account of their conduct.

Their great confidence is evidence that this brutality was no aberration. The aberration memorialized on this tape is the Los Angeles Police Department itself.

The department's rise to and fall from a position of great respect are not without precedent. When J. Edgar Hoover took command of the Federal Bureau of Investigation in 1924, it was a corrupt, politicized agency staffed by incompetents and hacks.

Hoover reformed the bureau by finding ways to insulate it - and himself - from electoral politics. He then hired fine young men, trained and equipped them well, made them answerable only to him, and, with great success, unleashed them on bandits and Nazi saboteurs. He took great pains to see that his agency and its men were portrayed favorably in both the entertainment and news media.

Eventually, the FBI ran into trouble. In the name of national security and tough law enforcement, patterns of abuse - illegal surveillance and intelligence files, improper provocations, entrapment, even burglaries - entered the bureau's repertoire.

Over 40 years, the political insulation and independence that had been so important in allowing the fledgling FBI to get its feet off the ground had allowed Hoover and the bureau to rise above all accountability.

Reform was necessary, and it occurred. No FBI head since Hoover has been "director for life." The bureau's personnel and administrative practices have been closely examined, and the people who run it no longer enjoy the power to make sure that agents follow the company line unquestioningly.

Accountability has replaced arbitrariness, and we all - including the bureau and its agents - are better off.

The Los Angeles Police Department's development follows this scenario by about 25 years.

In 1950, William Parker was named its chief on his condition that he enjoy autonomy from the City Hall that had corrupted the department. Given this independence (and despite the great animosity between Hoover and himself), Parker made the department an outstanding law-enforcement agency, closely modeled on the FBI.

The police department's great autonomy and Joe Friday image were necessary then, but they have long outlived their usefulness. Like Hoover's FBI, the Los Angeles Police Department must now be brought in line with democratic principles.

The King tape is not the first display of the department's freedom from accountability. The Los Angeles Police Department's ferocious and deadly 1975 confrontation with the Symbionese Liberation Army is still a subject of amazement among police in other, more restrained, places.

During one five-year stretch, twice as many Angelenos died after suffering police choke holds as in the 20 other largest American cities combined.

Without giving any advance warning to potential victims, officers of the Los Angeles Police Department's elite Special Investigations Section have watched suspects commit burglaries and armed robberies that police knew were going to occur, so that they could confront suspects afterward, often with bloody results.

And in a state where the mere possession of nunchuka - a lethal martial-arts device - is a felony comparable to possession of a switchblade knife, the department is embroiled in a lawsuit charging that officers unconstitutionally used this thug's weapon against peaceful anti-abortion demonstrators.

In short, for encouraging and tolerating brutality and excessive force, the Los Angeles Police Department has for several years been the outlaw among big American police departments.

In providing Bill Parker with the authority he needed to straighten out a badly bent police agency, Los Angeles' city fathers insulated it from any accountability to elected officials or the public. In essence, for more than 40 years, the chief of police has been answerable to nobody.

Some of his officers have learned that they need not worry about anybody's judgment but his. The record shows that this chief's judgments often have been indefensible.

The Los Angeles Police Department prides itself on its military organization, discipline and appearance. But as Gen. Douglas MacArthur discovered, even our greatest soldiers are accountable to elected officials.

The Los Angeles city government must find ways of making the police department and its chief accountable: In our system of justice, only the nine members of the Supreme Court should have no boss.

(James J. Fyfe is a professor of justice at American University in Washington and a former New York police lieutenant.)