In 1961, the Supreme Court, by a 5-to-4 vote, held for the first time that evidence illegally obtained by the police could not be admitted in a state criminal trial. This case-- Mapp v. Ohio--applied to state courts the so-called "exclusionary rule" that had governed criminal trials in federal courts since 1886. The controversy over the last 20 years about the merits of the rule has gradually led more and more federal judges to rethink its merits. It is about time.

The exclusionary rule is not part of the Constitution; it is a judge-made method to enforce constitutional precepts. Those precepts are the Fourth Amendment's guarantee that the persons, houses, papers, and effects of the American people shall be secure against "unreasonable searches and seizures" and the Fifth Amendment's prohibition against compelling a person to testify against himself. The theory is that if the police cannot use for prosecution evidence obtained by unreasonable searches or coerced confessions, they will have no incentive to gather evidence by improper means.

Certainly the case that gave rise to the Mapp rule shows that there was a problem of police misconduct about which something should be done. The Cleveland police broke into the home of a woman over her objections and without a warrant, manhandled and handcuffed her and searched her home. They had been looking for gambling paraphernalia, but found none; instead, they came upon some obscene pictures, for possession of which Miss Mapp was convicted. If that entry and search were not unreasonable, it is hard to see how anybody could be secure in his or her home.

But what began as a court correction of a manifestly improper search has come in time to be a complex, bewildering, and constantly shifting array of rules that tax the understanding of appellate judges, to say nothing of the police officer on the beat. Moreover, a rule designed to deter police misconduct has placed the burden of that deterrence on innocent third parties to such a degree that one must ask whether the deterrence obtained has been worth the price exacted.

It is not clear whether the exclusionary rule improves police behavior or by how much. There are studies that claim it has had little effect and others that claim it has had a great deal. In any event, it would be a mistake, I think, to argue that the rule has contributed materially to the increase in crime. Very few prosecutions for the kinds of crime we most fear--muggings, burglaries, robberies--involve searches that might be challenged as unreasonable or confessions that might be forced. A large fraction of the efforts by defense attorneys to exclude evidence they claim was illegally gathered occurs in trials of narcotics dealers, gamblers, pornographers and others engaged in consensual crimes.

What is clear is that the rule has become so complex as to be almost unintelligible. For example:

An officer may search without a warrant areas under "the immediate control" of an arrested person; this includes the room in which he was arrested but not other rooms in the house and not all the desk drawers in the room where the arrest occurred. But if the arrested person is taken into another room to get a shirt, the officer may search under the mattress in that room.

* An officer may search a handbag or billfold within reach of a companion of a person arrested, but not a billfold that is near the arrested person but that he cannot reach.

* An officer may search the front seat of an automobile in which a person was lawfully arrested and look under the front seat; he may even lift the lid off an unsecured cardboard box lying on the car's floor, but he may not search a sealed knapsack also lying on the floor nor luggage in the rear portion of station wagon.

* If, on knocking at a door of a place where the police thought cocaine might be sold, the officers hear the sound of a toilet flushing, they may enter without warrant to prevent the destruction of evidence, but when they knock and smell opium burning, they may not enter without a warrant.

* The police apparently can search around a person's barn without a warrant but not in a pile of Christmas trees 20 feet from a private lodge.

Moreover, the cost of deterring improper police conduct does not generally fall on the police. No officer is punished when the exclusionary rule is invoked; rather the prosecutor's case is lost. The officer is free to try again. If a guilty person goes free because improperly collected evidence that would have established his guilt is excluded, then the victim of the crime, and society at large, bear the costs of the police error. If an innocent person is prosecuted on the basis of evidence wrongfully gathered, then the exclusion of that evidence merely prevents the person's conviction, it does not compensate him for the wrongful prosecution. The exclusionary rule often operates as a kind of regressive tax that places the burden of attaining some public purpose on those least able to pay.

Sometimes that cost is small, as when other evidence exists, apart from that which was excluded, by means of which guilt or innocence can fairly be determined. But just as often the cost is very large, as when the whole case falls for want of the crucial fact. That occurs because the exclusionary rule, as Chief Justice Warren E. Burger phrased it, is a form of evidentiary capital punishment--an all-or-nothing proposition. The courts' view is that any police error, however trivial or unintended, requires the exclusion of that evidence, however important or even decisive.

There are at least three alternatives to the exclusionary rule.

First, it might be repealed altogether and other ways found of controlling police misconduct. This is what is done in Canada and all of Western Europe. Professor Stephen R. Schlesinger has proposed that judges order a hearing, separate from the trial, into alleged police misbehavior. An independent review board would be empowered to discipline the errant officer; meanwhile, the court could consider the tainted evidence on its merits in the criminal trial. Schlesinger would enable a wrongfully searched individual to recover monetary damages from the agency of which the officer was a member.

Some such policy as this is followed in other countries. It has the merit of separating the question of the guilt of the accused criminal from the issue of police behavior and ensuring that, if there was misbehavior, the appropriate parties bear the cost. It has the disadvantage of requiring the creation of new administrative procedures and encouraging more lawsuits against public officials, some of which would surely be frivolous. And it places part of the burden for initiating the correction of an abuse on the abused party.

A second alternative would be for the courts to give each state a choice between following the exclusionary rule and adopting some other method--perhaps Schlesinger's plan--to control police misconduct. This was the course urged by Justice Felix Frankfurter in 1949 when he wrote a Supreme Court opinion that refused to impose the exclusionary rule on the states, and it was the course suggested by Justice John Harlan in his dissent in the Mapp case. Neither justice approved of unreasonable searches or coerced confessions, but both felt that different states might be allowed to develop different remedies--provided each had some effective remedy. This approach has the advantage of allowing us to gather information we do not now have on the effectiveness of alternative ways of enforcing a constitutional guarantee.

A third alternative is the one recommended by the Attorney General's Task Force on Violent Crime, of which I was a member. It would retain a national exclusionary rule but modify its scope so as to permit the admission into a trial of any evidence gathered by an officer acting in the reasonable, good-faith belief that it was in conformity to the Constitution. A search conducted pursuant to a warrant would be prima facie evidence of such good faith. This would permit the courts to distinguish between blatant and technical violations of the Constitution, and to recognize that if the officer acts in good faith, the present exclusionary rule can have no deterrent effect whatsoever. It would minimize the extent to which police officers must master an almost incomprehensible body of case law that has evolved to judge each and every contingency that might arise during a search. It is a rule that would have protected Miss Mapp.

And it is a rule that a large number of federal judges have already embraced. In 1980, the federal Court of Appeals for the Fifth Circuit enunciated the "good faith" rule in the case of U.S. v. Williams. When the Supreme Court this year refused to hear the case, it implied that a majority of the justices did not find the Williams rule repugnant to their sense of the Constitution.

Whatever is done, it is a mistake to argue, as some militant civil libertarians have done, that the exclusionary rule in its present form is essential to the protection of our liberties. No other free society has the rule, and none seems notably less free for want of it. And the rule violates the first standard that ought to govern whatever connection is established between personal freedom and popular sovereignty--never ask the people to accept and defend a connection they cannot understand and that regularly leads them to deride the Constitution itself.