TEN YEARS AGO, if you were a big-city mayor with a slightly berserk police department on your hands, there was one preferred remedy. You hired Patrick V. Murphy for your chief.

It was almost a foregone conclusion that he would be available, because as quickly as he moved into a city forcibly retired the deadwood, promoted a cadre of young turks, and issue tough new marching orders guranteed to pound fear into any policeman who had even casually indulged in dishonesty or brutality, there would arise a powerful undercurrent of resentment. And it would soon occur to even the best-intentioned of local politicians, or to Murphy himself, that he was becoming dispensable.

So it was that this remarkable New York City policeman, whose father and two older brothers had been policemen before him, took command successively of the Syracuse, Washington, Detroit and New York City police departments - and lasted an average of barely a year and a half in each post. Given the shortness of his stays, and the size of the problems, the reforms effected under Murphy in these cities must have selective, and in some cases short-lived; but in the spectacularly demanding case of New York City, circa 1970, Murphy was unequivocally the man for the job, and he rose magnificently to the occasion.

In Commissioner: A View From the Top of American Law Enforcement, Murphy compares his own perception of police corruption in the late 1940s to Patrolman Frank Serpico's experiences in the late 1960s. Like Serpico, Murphy was assigned to a plainclothes vice unit, and was appalled by what he swathere. Like Serpico, he decided to alert the brass to the problem. But instead of shuffling around to various mid-level officials and outsiders, Murphy went right to the police commissioner, who listened politely and assured his young visitor, "You will be hearing from me."

Of course, Murphy never did hear from the commissioner, and for the next 15 years he plotted a career calculated to keep him as far removed as possible from further exposure to corruption. A number of those who later took key roles in Murphy's NYPD regime were, like him, Irishmen who had scrupulously maintained their personal integrity while doing little to raise the standards of their largely Irish department. It is probably not a coincidence that when the problem was finally attacked in earnest, the two men most responsible were an Italian and a Jew, Serpico and Sgt. David Durk.

Murphy's career could easily have yielded two or three books, but he seems to have decided to compress all his potential output into this one volume. The result is an odd but agreeable blend of autobiography, sociology, and nuts-and-bolts analysis of police traditions, whcih offers many fascinating glimpses into the somewhat exclusive world of the big-city police chief.

Althouhg some episodes are recounted with annoying diplomacy, in other cases Murphy reveals himself as a man of strongly held opinions. He portrays the majority of his fellow chiefs, for example, as men who adopt a tough rhetorical stance toward street shamelessly before mayors and cheap local politicians.

Murphy has even less respect, on the whole, for detectives. He deplores the popular image of the detective as "the brains of the outfit," and one of the first steps taken during his several stints as a police chief has been to downgrade the role of the detective while trying to upgrade that of the uniformed patrolman.

The FBI in the Hoover era may seem to be an agency immune to further deflation, but Murphy, from a novel perspective, has some novel criticisms, The FBI Academy, for instance, where rising young police executives have long been sent to professionalize themselves, is portrayed as Hoover's tool for rewarding policemen who kowtowed to the FBI. A degree from the FBI Academy used to be vitually a prerequisite to top-level police promotion, says Murphy, so the Bureau was able to assure the selection of local police chiefs who would do its will.

By such means, "almost single-handedly, Hoover slowed down the painful march out of Stone Age and kept and exploiting local police unmercifully," Murphy writes. "It was axiomatic. . . . that the FBI was to have unfettered access to local police files; but reciprocity was a different matter. It was also axiomatic with Hoover that investigations, begun, nurtured, and successfully wound up by local police, could, at last minute, with only marginal eleventh-hour help, be snatched away by the Bureau for publicity purposes."

As a police chief, Murphy souhgt to instill honesty and physical restraint among the troops, and discipline and a sense of accountability up throuhg the chain of command. His tactics were neither gradual nor subtle. Old-guard officials who seemed less than cooperative - and they were legion - would soon be demoted, transferred, encourage to retire, or severely dressed down.

In December, 1967, Murphy waspointed Washington's "Direcotor of Public Safety," a post created to get around civil service regulations that barred the selection of an ousider as police chief. The city's police officers, by all accounts, were not much happier with the appointment than was the incumbent chief, John B. Layton. But when Murphy istructed them to react coolly in the days that followed Martin Luther King's assassination, by and large they followed his instructions. Only two deaths were at the hands of police, both "clearly defensible," says Murphy.

"When a new police administrator comes into power, it is his immediate task to identify that faction which to the younger, more idealistic, more potentially productive officers in the ranks below appears to include the 'good' guys frozen out of the very top positions by the old guard clique," Murphy writes. Thus he regards it as one of his more significant accomplishments to have identified, and promoted, a "bright young commander named Jerry Wilson," who took over the D.C. department a year later.

In New York City, in 1971, one of the more drastic measures employed by Murphy and his anticorruption coordinator, William McCarthy, was to ply the ranks with internal spies, otherwise known as "field associates." Far from keeping this practise under wraps, Murphy and McCarthy did their best to convey a grossly exaggerated impression of the number of spies involved. On graduating from the police academy, rookies would routinely be invited up to McCarthy's outer office, where some would sit quietly the whole day long, and others would be summoned inside and signed up as field associates. Those not so honored would then be sent on to their precincts, where their colleagues would immediately assume, notwithstanding any denials, that they were now under officials surveillance and had better watch their steps.

Needless to say, such managerial innovations were not particularly calculated to win for Murphy the immediate and undying adulation of his troops. In New York and elsewhere, his arrival was quickly followed by what are known in the police trade as "morale problems." And it fell to his successors to attempt to calm fears and massage wounded egos, while "consolidating" Murphy-enacted reforms.

New York City was, remains, a special case among the nations's police departments, despite Murphy's contention that its problems invariably surface in other sizeable cities a few years later. Where else would detectives have invented a "Detective McCann" who, Murphy writes, "represented the wastebasket, i.e. trash can. If you ever had the experience of calling a detectives squad to inquire about the status of a case which you felt was not moving along with sufficient speed, you might have been told that it had been assigned to Detective McCann, who would get back to you as soon as possible. If you were pesistent enough, one of the detectives might even have impersonated Detective McCann on the phone."

As president since 1973 of the Police Foundation, a research group funded mainly by the Ford Foundation, Murphy has had an opportunity to pursue some of his most cherished beliefs about policing - his conviction, for example, that preventive patrol doesn't prevent much of anything. He has also been able to organize a network of liberal police chiefs in opposition to such nationally renowned tough guys as Philadelphia's Frank Rizzo and Los Angeles's Ed Davis. Some of these Murphy allies and proteges, men like Charles R. Gain, Joseph McNamara and Robert diGrazia, are following very much in Murphy's footsteps - shuttling from department to department, turning things upside down, generating fierce oppostion, and then, Lone-Ranger-like, riding off into the sunset to wreak their peculiar brand of havoc somewhere else.