Origins. Like most of the rest of the Bill of Rights, the Fourth Amendment has its origins in seventeenth-and eighteenth-century English common law. Unlike the rest of the Bill of Rights, the Fourth Amendment's origins can be traced precisely—it arose out of a strong public reaction to three cases from the 1760s, two decided in England and one in the colonies.
The two English cases are usefully treated as a pair. Both Wilkes v. Wood, 19 Howell's State Trials 1153 (C.P. 1763), and Entick v. Carrington, 19 Howell's State Trials 1029 (C.P. 1765), involved pamphleteers charged with seditious libel for criticizing the king's ministers and, through them, the king himself. In both cases, agents of the king issued a warrant authorizing the ransacking of the pamphleteers' homes and the seizure of all their books and papers. (An aside is necessary at this point: Warrants are means of giving government officials permission to search or arrest someone whom they otherwise might not be allowed to search or arrest. In American practice, warrants are issued only by judges or magistrates after reviewing an application from a police officer. In eighteenth-century England, warrants were sometimes issued by agents of the Crown on their own initiative.) These searches were duly carried out. Wilkes and Entick sued for damages, claiming that the warrants were void and that the searches pursuant to them were therefore illegal. Both Wilkes and Entick won, with powerful opinions issued by Lord Camden, the judge in both cases. These decisions made Camden a hero in the colonies; a number of towns and cities were named after him because of his opinions in Wilkes and Entick.
The third case was the Writs of Assistance Case (see Dickerson, 1939). British customs inspectors seeking to stamp out smuggling in colonial Boston were given blanket search warrants, called writs of assistance, that permitted them to search anyplace where they thought smuggled goods might be. (The writs also allowed the inspectors to compel private citizens to help them carry out the searches—hence the writs' name.) Some Boston merchants, represented by James Otis, sued, seeking a holding that the writs were invalid. The merchants lost, but Otis's argument, with its ringing defense of individual privacy, became famous and strengthened opposition to British rule. John Adams later said of Otis's argument that "then and there the child Independence was born."
Historians generally agree that the Fourth Amendment was designed to affirm the results in Wilkes and Entick, and to overturn the result in the Writs of Assistance Case. Three principles seem to follow. First, the government should not be allowed to search without some substantial justification, some reason to believe the place being searched contains the evidence being sought. That was the problem with the writs of assistance—they authorized searches based on no more than the unsupported suspicion of the inspector. Second, searches, particularly of private homes, should not go beyond their justification. That was the problem with the searches in Wilkes and Entick–the authorities did not simply search for and seize illegal writings, but took all the books and papers in the suspects' houses. Third, the government should not use blanket warrants to evade the first two principles. That was a problem in all three cases. English common law held it a trespass to invade someone's home without some kind of authorization; the warrants in Wilkes and Entick and the writs of assistance looked like efforts to evade that common law right. This explains why, at the time of the Founding era, search warrants—now viewed as a protection against police overreaching—were seen as more of a danger than a safeguard.
Notice that none of these three cases involved ordinary criminal law enforcement. None stemmed from the investigation of a murder, or a robbery, or a rape. Rather, each involved the investigation and prosecution of what might fairly be called dissidents—ordinary law-abiding citizens who disagreed strongly with the laws they were disobeying, and who enjoyed some substantial support among the citizenry. It is not at all clear from the Fourth Amendment's history that James Madison and his contemporaries wished to restrict the investigation of ordinary crimes; indeed, it is not clear that they even thought about the investigation of ordinary crimes.
Notice, too, that none of these cases involved searches by people whom we would recognize today as police officers. Police forces did not exist in the eighteenth century, either in England or in the colonies. It follows that the Framers could not possibly have thought about how best to regulate them. The Fourth Amendment's central role—reining in the police—is a role that it assumed much later. This point counsels in favor of a certain modesty when seeking to extract contemporary lessons from the Fourth Amendment's historical context.
The Fourth Amendment's text. The Fourth Amendment, along with the other provisions of the Bill of Rights, was proposed by James Madison. The version that was ultimately ratified (Madison's original version was slightly different) reads as follows:
The right of the people to be secure in their persons, 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.
The first clause—lawyers usually call it the "reasonableness clause"–contains a simple prohibition: unreasonable searches and seizures are forbidden. It leaves the key term, "unreasonable," undefined. The second clause, usually called the "warrant clause," places a set of limits on the issuance of search or arrest warrants. Three limits are listed: the warrants must be supported by probable cause, they must define where the search is to take place, and they must define what the object of the search is—who or what is to be seized.
This text nowhere requires the government to get search or arrest warrants—the second clause limits the use of warrants, but never says when, if ever, the government must use them. So far as the text of the Fourth Amendment is concerned, the police apparently may search or seize without a warrant, as long as the search or seizure is reasonable. This is unsurprising given the Fourth Amendment's origins. Madison and his contemporaries were chiefly concerned with preventing a recurrence of searches like the ones in Wilkes and Entick; the safest way to do that was to severely limit the use of warrants. Requiring them was apparently not on the Framers' agenda.
Subsequent history to 1961. For a century and a half after it was ratified, the Fourth Amendment (like the rest of the Bill of Rights) applied only to the federal government; state and local police were not bound by it. During most of this period, federal criminal investigation and prosecution was rare—there was no F.B.I., and no army of federal prosecutors—so there was little opportunity for Fourth Amendment litigation. As a consequence, Fourth Amendment law basically lay dormant until Prohibition in the 1920s, which for the first time produced a large and active federal enforcement bureaucracy. By that time, three important changes had taken place. First, the Supreme Court had adopted the exclusionary rule (in Weeks v. United States, 232 U.S. 314 (1914)), which held that illegally seized evidence ordinarily could not be used in criminal trials. The source and rationale of that rule are discussed in a separate entry. Second, during the course of the nineteenth century search warrants had come to be seen as a way of limiting police authority, not as means by which the government could evade legal restriction. This is a natural development: once the Fourth Amendment placed stringent limits on warrants, requiring warrants became a good way to ensure that police had good reasons for searching. Accordingly, one sees frequent discussion in Prohibition-era cases of the importance of requiring police to get advance permission from a magistrate, in the form of a warrant, before searching. Third, probable cause had become the generally applicable legal standard for searches. "Reasonable" searches meant searches supported by probable cause—which meant, roughly, a fair likelihood that the evidence searched for would be found in the place searched.
Thus, by the end of the 1920s, Fourth Amendment law had assumed the following structure. Probable cause was required for all searches or arrests. A warrant, obtained in advance, was required at least for searches of homes, and possibly for many other searches as well. (Curiously, arrests for serious crimes were not thought to require warrants, a rule that still holds today.) And these rules were enforced primarily by an exclusionary rule, so that when the police violated the rules, any evidence they found would be inadmissible in a subsequent criminal trial.
These rules still applied only to the federal government. That state of affairs changed when, in Wolf v. Colorado, 338 U.S. 25 (1949), the Supreme Court held that the Fourth Amendment was part of the liberty protected by the Fourteenth Amendment's due process clause against infringement by state and local officials. Twelve years later, in Mapp v. Ohio, 367 U.S. 643 (1961), the Supreme Court gave teeth to Wolf by imposing the exclusionary rule on the states. Henceforth local police, who are the primary enforcers of American criminal law, would be subject to the same search and seizure rules as F.B.I. agents, and to the same penalty for violating those rules.
It is not too much to say this worked a revolution in the way American police are themselves policed. Before 1961, local police were subject to state constitutional limits and could be sued for common law trespass (just like the offending officials in Entick and Wilkes). But these limits were illusory: state constitutions went unenforced, and common law claims against police officers virtually were never brought. Consequently, there was no working law of search and seizure, no body of rules that officers felt bound to obey, outside the federal system. Local police were restrained, if they were restrained at all, by local custom or politics. Law played no real part in their regulation.
This posed more of a danger to some suspects than to others. At the time Mapp was decided, it was widely (and surely correctly) believed that local police, especially in the South, treated black suspects much more harshly than white ones. And blacks could not protect their interests through the political process, because they were often either denied the right to vote or frozen out of governing coalitions. Although the opinions in Mapp do not make this point explicitly, it seems likely that one of the reasons—perhaps the primary reason—for the Supreme Court's assertion of regulatory control over local police was the desire to protect black suspects from unfair treatment at the hands of nearly all-white police forces. In this way, Fourth Amendment law, which began as a tool for protecting upperclass pamphleteers and smugglers, had become a means of protecting a poor minority against oppression by police forces dominated by a middle-class (white) majority.
After 1961. The law Mapp imposed on local police forces was basically the same law that had been imposed on federal agents enforcing Prohibition in the 1920s: probable cause for searches and arrests, with warrants required for searches unless the police had a good excuse for not getting one. Perhaps because of a coincidence in timing—at about the time Mapp was decided, crime rates began skyrocketing, with the number of serious felonies trebling in the course of the next decade—these rules came to seem too burdensome for increasingly busy local police. (Rising crime also meant rising public hostility to the Supreme Court's efforts to regulate the criminal process, which was seen as "handcuffing" police and prosecutors.) Beginning in 1968, the Supreme Court moved to relax these rules in two key ways. First, in Terry v. Ohio, 392 U.S. 1 (1968), the Court permitted police to "stop and frisk" suspects on the street based on reasonable suspicion of criminal activity, a lesser standard than probable cause. Terry involved suspicion of an about-to-be-committed robbery, but the Court soon applied its reasonable suspicion standard to past crimes and, most importantly, to drug crime. With these extensions, Terry meant that officers could briefly detain people, but not arrest them, based on fairly low-level suspicion of crime—the sort of suspicion that might come from spending time in the company of "known" drug dealers at places where drug trafficking is believed to be common.
The second change involved the warrant requirement. In a series of decisions stretching from the early 1970s to the early 1990s, the Court created or expanded various exceptions to the warrant requirement. For example, searches of cars were exempt, as were searches incident to arrest, as were inventory searches (these involved the inspection and cataloging of a suspect's belongings when he is taken into custody). These various exceptions, taken together, meant that the warrant requirement applied to searches of houses and apartments, but almost never applied to anything else. For searches and seizures outside private homes, police were still bound by the probable cause or reasonable suspicion standards, but no advance permission to search was required.
The creation and expansion of "stop and frisk" doctrine and the contraction of the warrant requirement were both contentious; Fourth Amendment decisions in the 1970s and 1980s gave rise to some of the most heated arguments the Supreme Court has ever seen. Defenders of Fourth Amendment law's classical structure, primarily Justices William Brennan and Thurgood Marshall, argued passionately that it was important to preserve probable cause, not the softer reasonable suspicion standard, as the primary standard for searches and seizures; they also argued for a broad warrant requirement to provide an extra check on police overreaching. But these arguments generally lost, and the structure that had emerged by the early 1990s is now fairly stable. The key characteristics of that structure are the subject of the next part.