"Unreasonable" is the controlling word in the fourth amendment. In its first clause the amendment guarantees the right of the people to be free from unreasonable searches and seizures; its second clause stipulates the terms for issuance of a judicial warrant: probable cause, oath or affirmation, particularity of description. What is an unreasonable and therefore forbidden search? Conversely, what is a reasonable and permitted one? The amendment does not say. The answer, in large measure, depends on one's understanding of the relationship of the two clauses.
Two polar positions have dominated debate in the Supreme Court on this matter. The view that was in the ascendancy before 1946 and that has generally prevailed again since chimel v. california (1969), treats the two clauses in conjunction so that the unreasonable searches forbidden by the first clause are defined by the warrant requirements in the second clause: a reasonable search is one conducted subject to a proper warrant, an unreasonable search is one that is not. A second view, generally dominant between harris v. united states (1946) and 1969, holds that reasonableness is an autonomous principle, to be measured by all the circumstances rather than by the securing of a warrant (although this is one factor to be considered).
The conflict between the two readings of "unreasonable" essentially has centered on search incident to arrest, a recognized "emergency" exception to the warrant requirement since weeks v. united states (1914). According to the second interpretation, once the privacy of the dwelling has legitimately been invaded to make a lawful arrest, it is reasonable to allow the search (for the purpose of disarming the arrestee and seizing evidence which he may seek to destroy) to blanket the entire premises in which the arrest was made. This is a matter of the greatest consequence, for the vast majority of searches are carried out incident to arrest. If, however, the warrant requirement is considered to be the core of the amendment, the search must be circumscribed to the extent required by the emergency and therefore confined to the person arrested and the area within his immediate reach.
To treat reasonableness as an independent standard is contrary to both history and logic. On logical grounds there seems little value to stringent warrant requirements that can be readily negated by "reasonable" warrantlesssearches. History, too, sets its face against the notion. The Fourth Amendment's proscription of unreasonable searches, alone among the provisions of the bill of rights to set fair standards for the apprehension and trial of accused persons, has a rich historical background in American, as well as English, experience. The amendment is rooted in the restrictions which seventeenth-and eighteenth-century common law judges in England placed on the search power (for example, wilkes cases, 1763–1770). This power had been abused through the government's relentless hunt for political and religious dissidents during a phase of English history well understood in the colonies. The amendment stems more directly from the public outcry against indiscriminate searches for smuggled goods (authorized by general warrants known as writs of assistance) during the last years of the colonial period in America, notably in Massachusetts. The main object of the Fourth Amendment, to prevent the recurrence of the detested general warrant, was to be accomplished by placing strict limits on the issuance of a warrant. The reasonableness clause, as seems clear from the historical record of the amendment's drafting in the first Congress, was meant to reemphasize, and perhaps strengthen, the warrant requirements in the second clause. To detach the reasonableness clause from the warrant clause by infusing it with independent potency serves to dilute the amendment's protection, exactly the opposite of the result its framers intended. It is insufficient to leave the initial determination of reasonableness to the police, with judicial review taking place retrospectively when the prosecutor seeks to introduce the fruits of the search in evidence. Many searches will produce no evidence, and even when evidence is found, the pressure on judges to rule against obviously guilty defendants will be great despite the illegality of the searches.
Consonant with the amendment's history, the Court at one time assigned an even broader meaning to "unreasonable" than is taken by the first view. In boyd v. united states (1886) the Court held that private papers are immune to seizure even under warrant—on the theory that one test of the reasonableness of a search is whether or not its purpose is to seize evidence that will force the person to incriminate himself. In contrast, contraband goods and fruits and instrumentalities of crime are deemed seizable because their possessor has no legal property right in them. In Gouled v. United States (1921) the Court logically extended the immunity granted private papers to all kinds of evidentiary materials (for example; clothing). However, this mere evidence rule, as it came to be known, was overturned as "wholly irrational" in warden v. hayden (1967), and probably little remains of the immunity granted to private papers (Fisher v. United States, 1976).
Other exigent circumstances, in addition to search incidental to arrest, which, in either view, permit the police to bypass the warrant requirement, include the rule of carroll v. united states (1925), which permits the search of a moving vehicle on probable cause to believe that it is transporting contraband; the ruling in Schmerber v. California (1966), which permits the compulsory taking of a blood sample from a driver to measure its alcoholic content where there is probable cause to believe he was intoxicated while driving; and the rule of Warden v. Hayden (1967), which permits the "hot pursuit" of a felon into a dwelling. Even in the absence of evidence that a crime has been committed, where the suspicious conduct of an individual leads an officer to believe that he or others are in danger and imminent action is imperative, he may stop the suspect and "frisk" the individual's outer clothing in order to disarm him of weapons he may be carrying. (See terry v. ohio.)
In the case of search incidental to arrest, hot pursuit, or stop and frisk, the emergency is self-evident, but it is no less genuine in the case of a moving vehicle or a blood test, for the delay involved in the obtaining of a warrant will usually defeat the object of the search. The automobile might by that time be far away, perhaps in another jurisdiction, and the percentage of alcohol in the blood gradually diminishes once intake ceases. These are only examples. Clearly any real emergency, as the sound of a shot or a cry for help coming from behind closed doors, would justify a warrantless search by the police.
The only kinds of searches known to the framers, and to which the Fourth Amendment was originally addressed, contained two elements: (1) entry into the dwelling (2) for the purpose of seizing evidence of crime. At first the Court considered the definition of search to be governed by this experience and maintained that warrants were not required for more modern types of searches that lacked one or the other of these elements. Thus searches for oral utterances conducted by wiretapping which do not involve entry onto premises, as in olmstead v. united states (1928), or inspection of dwellings to uncover nuisances to public health or safety, as in Frank v. Maryland (1959), were held not to be covered by the amendment. Subsequently, however, electronic eavesdropping (including wiretapping) and administrative searches were both brought under the amendment's protective umbrella in katz v. united states (1967) and camara v. municipal court (1967), respectively. But a visit to the home by a caseworker for the purpose of determining whether a public assistance grant is being properly used does not amount to an unreasonable search and requires no warrant, as the Court held in wyman v. james (1971).
A court order for the surgical removal of a bullet from the body of a suspect was ruled unreasonable in Winston v. Lee (1985)—at least when the need for the evidence is not "compelling"—because of the serious intrusion on privacy and the medical risks entailed.
In order to prevent the Fourth Amendment from being reduced to a mere parchment guarantee, evidence obtained through unreasonable search has since 1914 been excluded from trials in the federal courts (Weeks v. United States), and in the state courts as well since mapp v. ohio (1961). (See exclusionary rule.) Although the amendment contains no express command of exclusion, it has been construed to authorize the judiciary to apply such sanctions as are necessary to ensure compliance with the standard of reasonableness.
Like the rest of the Bill of Rights, the ban on unreasonable searches was originally intended to place restrictions only on the federal government. That ban became applicable to the states, as an element of fourteenth amendment due process, in 1961 (Mapp v. Ohio), and the same standard of reasonableness now governs searches made by federal and state authorities (ker v. california, 1963).
(See incorporation doctrine.)
Jacob W. Landynski
Fellman, David 1976 The Defendant's Rights Today. Pages 277–284. Madison: University of Wisconsin Press.
——1971 "The Supreme Court's Search for Fourth Amendment Standards: The Warrantless Search." Connecticut Bar Journal 45:2–39.
Levy, Leonard W. 1974 Against the Law. Pages 75–117. New York: Harper & Row.