In June, the Supreme Court decided that Detroit police did not violate the Fourth Amendment rights of a drug dealer named Booker Hudson when they entered his home in August 1998 only five seconds after announcing their presence at his door. Hudson's lawyers argued that--although he had a loaded gun hidden in the couch next to him--police should have waited to enter for at least 20 seconds after knocking. The four dissenting justices in Hudson v. Michigan complained that the decision repealed a "knock and announce" rule that has been part of common law since the 13th century. Newspapers around the country echoed their lament.

Justice Scalia, writing the majority opinion, took aim at a rule of more recent vintage--the "exclusionary rule," enshrined by the Supreme Court only a generation ago, which holds that evidence must be excluded from trial if it has been obtained improperly. Dismissing key evidence on such a minor point as the number of seconds police wait at the door is the equivalent of giving the defendant a "get-out-of-jail-free card," wrote Scalia. The suppression of evidence should be "our last resort, not our first impulse."

Unfortunately, Justice Anthony Kennedy, who otherwise sided with the majority, did not endorse Scalia's rejection of the exclusionary rule. In a separate opinion, Kennedy called this rule "settled" and "not in doubt," but held that in this particular case the police did not overstep. Scalia's frontal assault on the exclusionary rule, though, now has the support of four justices. Before long, this judge-invented rule that redefined American law enforcement over the past half-century may reach the end of its long run.

Its origins were certainly humble. On May 23, 1957, three Cleveland police officers came to the door of Dollree Mapp, who was suspected of harboring a suspect in a bombing case. (The bomb had gone off on the front porch of Don King's house--a warning to the future boxing promoter from rivals in the numbers racket.) Mapp called her lawyer, who told her not to allow the police to enter without a warrant.

The officers departed. Three hours later they returned with reinforcements, waving a piece of paper in front of her face and saying it was a warrant (whether it was remains in dispute). Mapp grabbed the paper and stuffed it in her dress. The police wrestled it back and put her in handcuffs. Her lawyer arrived but was not allowed to speak to her or enter the house. For the next few hours, police ransacked Mapp's home but didn't find their fugitive. In the basement, however, they did discover a suitcase that Mapp said belonged to a former tenant. Inside were four pamphlets, a couple of photographs, and a pencil doodling alleged to be obscene. Mapp was convicted of possession of pornographic material and sentenced to two to seven years in prison.

When Dollree Mapp's case came before the Supreme Court in 1961, search and seizure was not even the issue. Her conviction was appealed as a challenge to Ohio's strict pornography laws, and that was the subject of oral arguments. But President Kennedy had just elevated his secretary of labor Arthur Goldberg to the bench to replace Felix Frankfurter, and for the first time the liberal faction led by Chief Justice Earl Warren had a majority. Without any preliminaries, the new majority seized on Mapp v. Ohio as an opportunity to do something it had contemplated a long time--extend the federal exclusionary rule on search and seizure to state criminal cases.

The Fourth Amendment to the Constitution reads as follows:

The right of the people to be secure in their person, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.

Until the 20th century, however, the Bill of Rights was interpreted as applying only to the federal government, not the states. This limited the scope of the Fourth Amendment, since most criminal investigations are conducted at the state and local level.

The exclusionary rule was adopted for federal cases in a 1914 decision, Weeks v. United States. Fremont Weeks had been convicted of participating in a lottery through the mails, based on evidence seized from his Kansas City home without a warrant. Investigators had borrowed a key from a neighbor and searched his house, seizing evidence and other prop erty. Weeks sued to have his property returned and the evidence excluded from the case. The Supreme Court, breaking with common law tradition, ruled in his favor. The "exclusionary rule" was promulgated as a remedy to deter violations of the Fourth Amendment. Benjamin Cardozo, then a New York state judge and soon to be on the Supreme Court, spotted the flaw right away: "The criminal goes free because the constable has blundered," he famously wrote. (The traditional remedy for a warrantless search was a civil suit for damages. See Stanley C. Brubaker's discussion in these pages, "The Misunderstood Fourth Amendment," March 6, 2006.)

Over the next four decades, federal agents skirted the new rule by having state and local police gather evidence, handing it over in what became known as the "silver platter doctrine." While the FBI was circumscribed, state and local police forces were unrestrained by the Fourth Amendment. And so the Supreme Court decided to crack down. By a 5-to-4 vote, Mapp v. Ohio applied both the Fourth Amendment and the exclusionary rule to the states. Law enforcement has never been the same.

Mapp was the first of the Warren Court decisions that introduced the phrase "overturned on technicalities" into our language. Miranda v. Arizona, governing criminal confessions, is better known for introducing the phrase "you have the right to remain silent" and excluding numerous seemingly authentic confessions. But the exclusionary rule has had a greater effect on policing. Even today, many a criminal will confess to a crime to "get it off his chest." Even if he later thinks better of it, and claims he was coerced, the jury will usually be allowed to hear the confession and sort out the truth.

Mapp, however, involves physical evidence. Murder weapons, drug caches, even dead bodies turned up in police searches can be excluded from a case forever. In such instances, prosecution becomes impossible. Before Mapp, the "fundamental fairness" of a trial was viewed as the ultimate standard for deciding procedural issues. Since the decision, the courts have become endlessly bogged down in technicalities--such as how many seconds the police must wait before entering a home after knocking.

One of the first people to recognize this profound difference was Alan Dershowitz, who was clerking for Justice Goldberg when Mapp was decided. In his book The Best Defense (1983), Dershowitz recounts how as a defense attorney he learned to "put the state on trial" so that the conduct of the police, rather than the criminal, becomes the focus of the trial. Candidly admitting that nearly all his clients were guilty, Dershowitz told how he was able to spring numerous clients by arguing the minutiae of searches and seizures. His greatest triumph came in 1984, when he got a reversal of the conviction of socialite Claus von Bülow for the attempted murder of his wife. The family of Sunny von Bülow, who was left in a coma from an insulin overdose, had hired a private detective to search their home, uncovering a "black bag" containing hypodermic needles and other incriminating evidence. Dershowitz successfully argued that Rhode Island police should have obtained a warrant in order to accept evidence from the private detective. Without the evidence, von Bülow was acquitted at a second trial.

In the early years of the Mapp era, countless search warrants were overturned because of a misspelled name, a faulty street address, or transposed license plate numbers. In New Hampshire, a child murderer was freed because his wife had allowed police to search the house without his permission. "Evidentiary hearings" became the standard opening round of any criminal prosecution, and countless cases collapsed when technical violations by the police made key evidence inadmissible. A particular favorite of defense lawyers was the Fourth Amendment phrase "describing the place to be searched, and the persons or things to be seized." What constitutes an accurate "description" of evidence? Such a question could occupy philosophy students for whole semesters. If the warrant specifies a 9mm Smith & Wesson and the gun turns out to be a .357 Magnum, is it admissible? Police over time learned ways to fudge such details, but the result was constant hair- splitting.

At worst, the exclusionary rule could become a simple excuse for judges to impose their will. In the 1970s and '80s, for example, the California Supreme Court under Chief Justice Rose Bird, openly hostile to capital punishment, overturned dozens of death penalty convictions. With metronomic regularity, the court would rule that a warrant had not sufficiently "described the place to be searched and persons or things to be seized." One notorious 1985 case finally led to the removal from the court of Bird and two colleagues by disgusted California voters. It involved Dr. Theodore Frank, a convicted child molester who had tortured and murdered a two-year-old girl. In the warrant, police had specified that they would search for "writings which could relate to the death of [the girl] and would indicate either participation and/or an interest in that death by Theodore Frank." What they discovered was a diary in which Frank confessed his fetishes. ("I want to give pain to these little children. I want to harm them.") The writings were read to the jury at the penalty phase, and Frank received a death sentence. Upon review, the Bird court ruled the warrant had been "overbroad," mere "boilerplate" that allowed police to "rummage" through Frank's possessions. They overturned the death sentence.

In 1984, an egregious Massachusetts case arrived before the Supreme Court. The bound and burnt body of a 25-year-old woman named Sandra Boulware had been found in a vacant lot in Boston. Her boyfriend, 45-year-old Osborne Sheppard, was implicated. Police obtained a warrant to search his apartment. Among other things, the warrant specified "a woman's jacket that has been described as black-gray (charcoal), any possessions of Sandra D. Boulware, similar type wire and rope that match those on the body of Sandra D. Boulware. . . . A blunt instrument that might have been used on the victim, men's or women's clothing that may have blood" on them, and so on. What they found was "a pair of bloodstained boots, bloodstains on the concrete floor, a woman's earring with bloodstains on it, a bloodstained envelope, a pair of men's jockey shorts and women's leotards with blood on them, three types of wire, and a woman's hairpiece, subsequently identified as the victim's." The Massachusetts Supreme Court threw out the conviction on the grounds that the warrant had not adequately described the "things to be seized."

The Supreme Court finally put an end to this nonsense, carving out a "good faith exemption" to the exclusionary rule. If the police thought they were acting in good faith in conducting the search, then the evidence could be admitted. But of course this vague rule only opened up more opportunity for semantics. Whose "good faith" was involved? The police or the judge who issued the warrant? What constitutes "good faith"? That was for future courts to debate.

Meanwhile, defense attorneys moved on to new terri tory. The phrase of choice became "probable cause." Yes, a warrant might have been issued in good faith, and yes, the warrant might sufficiently describe the persons or things to be seized. But was there "probable cause" for issuing it?

Here's a good example. In the 1971 Academy Award-winning movie The French Connection, New York City drug detective "Popeye" Doyle and his partner see a small-time mobster celebrating with a party of friends at the Copacabana. "Something doesn't look right," he says, and they decide to follow the party home. They stake out the residence and eventually uncover the biggest drug shipment ever to reach New York City--a true story.

Such an investigation would be blatantly unconstitutional under today's standards, and all the evidence would likely be thrown out. Police cannot stake out a person's home, even a mobster's, because "something doesn't look right." They cannot follow hunches or investigate because a person "looks suspicious." For the most part, they must have evidence that a crime is being committed. When they seek a warrant, they must have specific, detailed knowledge of what they expect to find.

Of course, this philosophy of policing finally came home to roost in August 2001, when Minnesota FBI agents arrested Zacarias Moussaoui, an alien with an expired visa who had aroused the suspicion of flight school instructors in Minneapolis because he wanted to learn to fly a commercial jet without having any interest in how to take off or land. Dutifully following established procedures, the Minneapolis agents applied to Washington for a search warrant to look into his computer. FBI lawyers there turned down the request. There was no "probable cause" for investigating any further. All they had was a suspicious guy with an expired visa taking flight lessons. After forty years of playing Russian roulette with the American public, the criminal justice system finally hit a loaded chamber.

What makes the exclusionary rule so absurd is that it only protects people who are guilty of crimes. If the police come to your house, knock down your door, ransack your home, throw all your belongings in the street, and find no incriminating evidence, then the exclusionary rule offers you no compensation whatsoever. Only if evidence turns up that shows you to be guilty of something are you rewarded.

In pointing out how dated the exclusionary rule has become, Justice Scalia noted both the "increasing professionalism of police forces" and the ease with which aggrieved citizens can now pursue other remedies against the police for the violation of their rights. "Citizens whose Fourth Amendment rights were violated by federal officers could not bring suit until 10 years after Mapp," Scalia noted. Since then, "Congress has authorized attorney's fees for civil-rights plaintiffs. . . . The number of public-interest law firms and lawyers who specialize in civil-rights grievances has greatly expanded. . . . [E]xtant deterrences against [Fourth amendment violations] are . . . incomparably greater than the factors deterring warrantless entries when Mapp was decided. Resort to the massive remedy of suppressing evidence of guilt is unjustified."

After 45 years, the misbegotten practice of freeing the criminal because the constable has blundered may finally be about to come to an end.

William Tucker is author of Vigilante: The Backlash Against Crime in America.

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