Reasonable Expectation of Privacy

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An issue of extraordinary importance in determining the scope of the protection of the fourth amendment is the interpretation of the word "searches" in that amendment's proscription of "unreasonable searches and seizures." If certain conduct of state or federal officials is deemed not to constitute either a search or seizure, then Fourth Amendment requirements need not be met. On the other hand, if that activity is a search or seizure, then it is unconstitutional unless those requirements—that the conduct be undertaken only upon a certain quantum of evidence (probable cause), and in many instances that it be undertaken only upon prior judicial approval—have been met. How this issue comes out is a matter of considerable practical significance in criminal prosecutions, for the Fourth Amendment's exclusionary rule usually dictates suppression of evidence if the amendment's limitations were exceeded in acquiring it.

The Supreme Court has had difficulty in developing a workable definition of the word "searches." At an earlier time, as in Hale v. Henkel (1906), the Court was inclined to say that "a search ordinarily implies a quest by an officer of the law," yet it soon became clear that not every instance of seeking evidence was a search. In olmstead v. united states (1928), for example, the Court held that the placing of a tap on telephone wires and thereby eavesdropping on the defendant's conversations was no search. As the Court later explained in silverman v. united states (1961), there was no Fourth Amendment search unless the police had physically intruded into "a constitutionally protected area." These areas were enumerated in the Fourth Amendment itself: "persons," including the bodies and clothing of individuals; "houses," including apartments, hotel rooms, garages, business offices, stores, and warehouses; "papers," such as letters; and "effects," such as automobiles. But then came the landmark decision of katz v. united states (1967), which overruled the Silverman standard and gave birth to the "reasonable expectation of privacy" test.

Katz was convicted in federal court on a charge of transmitting wagering information by telephone in violation of federal law. At trial the government was permitted to introduce, over defendant's objection, evidence of his end of telephone conversations, overheard by FBI agents who had attached an electronic listening and recording device to the exterior of a public telephone booth from which Katz habitually placed long-distance calls. The court of appeals affirmed Katz's conviction, reasoning that the electronic eavesdropping did not amount to a Fourth Amendment search because the microphone had not penetrated the wall of the telephone booth. Before the Supreme Court, the parties disputed whether the booth was a "constitutionally protected area," but the Court declined to address that issue, noting that "the Fourth Amendment protects people, not places. What a person knowingly exposes to the public, even in his home or office, is not a subject of Fourth Amendment protection.… But what he seeks to preserve as private, even in an area accessible to the public, may be constitutionally protected." The Court then held, "The Government's activities in electronically listening to and recording the petitioner's words violated the privacy upon which he justifiably relied while using the telephone booth and thus constituted a "search and seizure' within the meaning of the Fourth Amendment."

In his concurring opinion in Katz, Justice john m. harlan joined the opinion of the Court, but then explained what he took this opinion to mean. Lower courts and ultimately the Supreme Court itself came to rely upon the Harlan elaboration of the Katz test: "My understanding of the rule that has emerged from prior decisions is that there is a twofold requirement, first that a person have exhibited an actual (subjective) expectation of privacy and, second, that the expectation be one that society is prepared to recognize as "reasonable." Courts and commentators thereafter attempted to ascertain the meaning of each of these two requirements.

The first part of the Harlan formulation arguably finds support in that part of the Katz majority opinion which declared that the government conduct directed at Katz "violated the privacy upon which he justifiably relied." However, an actual, subjective expectation of privacy deserves no place in a statement of what the Fourth Amendment protects. By use of a subjective test, it would be possible for the government by edict or known systematic practice to condition the expectations of the populace in such a way that no one would have any real hope of privacy. Harlan later appreciated this point, observing in his dissent in united states v. white (1971) that analysis under Katz must "transcend the search for subjective expectations," for "our expectations, and the risks we assume, are in large part reflections of laws that translate into rules, the customs and values of the past and present."

Although a majority of the Court acknowledged in Smith v. Maryland (1979) that in some situations the subjective expectation of privacy test "would provide an inadequate index of Fourth Amendment protection," the Court sometimes appears to rely on it nevertheless. Illustrative is California v. Ciraolo (1986), holding that the Fourth Amendment was not violated by warrantless aerial observation of marijuana plants inside a fenced backyard of a home. Though the state conceded the defendant had a subjective privacy expectation, the Court offered the gratuitous observation that because "a 10-foot fence might not shield these plants from the eyes of a citizen or a policeman perched on the top of a truck or a 2-level bus," it was "not entirely clear" whether the defendant "therefore maintained a subjective expectation of privacy from all observations of his backyard, or whether instead he manifested merely a hope that no one would observe his unlawful gardening pursuits." The unfortunate implication of this comment is that a defendant cannot even get by the first Katz hurdle unless he has taken steps to ensure against all conceivable efforts at scrutiny.

The second branch of the Harlan elaboration in Katz, apparently an attempt to give content to the word "justifiably" in the majority's formation, prompted the Court on later occasions, as in terry v. ohio (1968), to refer to the Katz rule as the "reasonable 'expectation of privacy' test." This language is perhaps unfortunate, for it might be read to mean that police activity constitutes a search whenever it uncovers incriminating actions or objects which the law's hypothetical reasonable man would expect to be private—that is, which as a matter of statistical probability were not likely to be discovered. Though the Court has wisely rejected such an interpretation, as in oliver v. united states (1984), it still leaves the question of precisely what makes a reliance on privacy "justified" in the Katz sense.

In his White dissent, Harlan asserted that this question must "be answered by assessing the nature of a particular practice and the likely extent of its impact on the individual's sense of security balanced against the utility of a conduct as a technique of law enforcement." Thus, he added, "those more extensive intrusions that significantly jeopardize the sense of security which is the paramount concern of Fourth Amendment liberties" are searches. Anthony Amsterdam has similarly asserted that the "ultimate question" posed by Katz "is whether, if the particular form of surveillance practiced by the police is permitted to go unregulated by constitutional restraints, the amount of privacy and freedom remaining to citizens would be diminished to a compass inconsistent with the aims of a free and open society."

But this is unfortunately not how the Court has subsequently interpreted Katz, as is apparent from a sampling of more recent cases. In United States v. Miller (1976) the Court held that a person has no justified expectation of privacy in the records of his banking transactions kept at financial institutions with which he has done business, because the documents "contain only information voluntarily conveyed to the banks and exposed to their employees in the ordinary course of business." This conclusion overlooks the fact that bank employees examine checks briefly and one at a time, and thus do not construct conclusions about the customer's lifestyle, while police who study the totality of one's banking records can acquire a virtual current biography. The Court's error in Miller was compounded in Smith v. Maryland, holding that one has no legitimate expectation of privacy in the numbers he dials on his telephone because those numbers are conveyed to the telephone company's switching equipment and, in the case of long-distance calls, end up on the customer's bill. Thus, the defendant in Smith could not object to police use of a pen register to determine all numbers he dialed, though once again the more focused police examination of the information revealed much more than the limited and episodic scrutiny that the phone company employees might give the same numbers.

In United States v. Knotts (1983) the Court similarly held that it was no search for police to keep track of a person's travels by using a "beeper" because "anyone who wanted to look" could have learned, without such assistance, of the defendant's 100-mile journey from Minneapolis into rural northern Wisconsin. But to learn what the beeper revealed—that the beeper-laden container of chemicals purchased in Minneapolis was now in a particular secluded cabin 100 miles away—would have taken an army of bystanders in ready and willing communication with one another. And then there is Ciraolo, holding that it is no search for police to look down from an airplane into one's solid-fenced backyard because "any member of the public flying over this airspace who glanced down could have seen everything that these officers observed." This ignores the fact, as the four dissenters put it, that "the actual risk to privacy from commercial or pleasure aircraft is virtually nonexistent."

In each of these cases, a majority of the Court failed to appreciate that "privacy is not a discrete commodity, possessed absolutely or not at all" (as Justice thurgood marshall put it in his Smith dissent) and that there is a dramatic difference, in privacy terms, between the sporadic disclosure of bits and pieces of information to a small and often select group for a limited purpose and a focused police examination of the totality of that information regarding a particular individual. Such decisions leave the promise of Katz unrealized and ignore the teachings of the Supreme Court's germinal search and seizure decision, boyd v. united states (1886). There, Justice joseph p. bradley wrote that "constitutional provisions for the security of person and property should be liberally construed" in order to forestall even "the obnoxious thing in its mildest and least repulsive form," as "illegitimate and unconstitutional practices get their first footing in that way, namely, by silent approaches and slight deviations from legal modes of procedure."

Some hope—modest, given the outcome of the case—is to be found in Florida v. Riley (1989), holding that an officer's naked-eye observation into the defendant's residential greenhouse from a helicopter 400 feet off the ground was no search. Significant for present purposes is the observation of Justice harry a. blackmun, dissenting, that a "majority of the Court" (the four dissenters and one concurring Justice) believe that the reasonableness of the defendant's expectations "depends, in large measure, on the frequency of nonpolice helicopter flights at an altitude of 400 feet." This means, Justice william j. brennan concluded in his dissent, that a majority of the Court does not accept "the plurality's exceedingly grudging Fourth Amendment theory, [whereunder] the expectation of privacy is defeated if a single member of the public could conceivably position herself to see into the area in question without doing anything illegal." Riley thus may signal a rejection of the all-or-nothing approach to privacy, thereby giving the Katz reasonable expectation of privacy test new meaning.

Wayne R. La f ave

(see also: Open Fields Doctrine; Plain View Doctrine; Right of Privacy; Search and Seizure; Unreasonable Search; Warrantless Searches; Wiretapping.)


Amsterdam, Anthony G. 1974 Perspectives on the Fourth Amendment. Minnesota Law Review 58:349–477.

Gutterman, Melvin 1988 A Formulation of the Value and Means Models of the Fourth Amendment in the Age of Technologically Enhanced Surveillance. Syracuse Law Review 39: 647–735.

Junker, John M. 1989 The Structure of the Fourth Amendment: The Scope of the Protection. Journal of Criminal Law and Criminology 79:1105–1184.