The Interest Protected

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 Interest Protected.—For the Fourth Amendment to apply to a particular set of facts, there must be a “search” and a “seizure,” occurring typically in a criminal case, with a subsequent attempt to use judicially what was seized.30 Whether there was a search and seizure within the meaning of the Amendment, and whether a complainant’s interests were constitutionally infringed, will often turn upon consideration of his interest and whether it was officially abused. What does the Amendment protect? Under the common law, there was no doubt. In Entick v. Carrington,31 Lord Camden wrote: “The great end for which men entered in society was to secure their property. That right is preserved sacred and incommunicable in all instances where it has not been taken away or abridged by some public law for the good of the whole. . . . By the laws of England, every invasion of private property, be it ever so minute, is a trespass. No man can set foot upon my ground without my license but he is liable to an action though the damage be nothing . . . .” Protection of property interests as the basis of the Fourth Amendment found easy acceptance in the Supreme Court32 and that acceptance controlled the decision in numerous cases.33 For example, in Olmstead v. United States,34 one of the two premises underlying the holding that wiretapping was not covered by the Amendment was that there had been no actual physical invasion of the defendant’s premises; where there had been an invasion—a technical trespass— electronic surveillance was deemed subject to Fourth Amendment restrictions.35

The Court later rejected this approach. “The premise that property interests control the right of the government to search and seize has been discredited. . . . We have recognized that the principal object of the Fourth Amendment is the protection of privacy rather than property, and have increasingly discarded fictional and procedural barriers rested on property concepts.”36 Thus, because the Amendment “protects people, not places,” the requirement of actual physical trespass is dispensed with and electronic surveillance was made subject to the Amendment’s requirements.37

The new test, propounded in Katz v. United States, is whether there is an expectation of privacy upon which one may “justifiably” rely.38 “What a person knowingly exposes to the public, even in his own 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.”39 That is, the “capacity to claim the protection of the Amendment depends not upon a property right in the invaded place but upon whether the area was one in which there was reasonable expectation of freedom from governmental intrusion.”40

Katz’s focus on privacy was revitalized in Kyllo v. United States,41 in which the Court invalidated the warrantless use of a thermal imaging device directed at a private home from a public street. The rule devised by the Court to limit police use of new technology that can “shrink the realm of guaranteed privacy” is that “obtaining by sense-enhancing technology any information regarding the interior of the home that could not otherwise have been obtained without physical ‘intrusion into a constitutionally protected area’ . . . constitutes a search—at least where (as here) the technology in question is not in general public use.”42 Relying on Katz, the Court rejected as “mechanical” the Government’s attempted distinction between offthewall and through-the-wall surveillance. Permitting all offthewall observations, the Court observed, “would leave the homeowner at the mercy of advancing technology—including technology that could discern all human activity in the home.”

Although the sanctity of the home has been strongly reaffirmed, protection of privacy in other contexts becomes more problematic. A two-part test that Justice Harlan suggested in Katz often provides the starting point for analysis.43 The first element, the “subjective expectation” of privacy, has largely dwindled as a viable standard, because, as Justice Harlan noted in a subsequent case, “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.”44 As for the second element, whether one has a “legitimate” expectation of privacy that society finds “reasonable” to recognize, the Court has said that “[l]egitimation of expectations of privacy by law must have a source outside of the Fourth Amendment, either by reference to concepts of real or personal property law or to understandings that are recognized and permitted by society.”45

Thus, protection of the home is at the apex of Fourth Amendment coverage because of the right associated with ownership to exclude others;46 but ownership of other things, i. e., automobiles, does not carry a similar high degree of protection.47 That a person has taken normal precautions to maintain his privacy, that is, precautions customarily taken by those seeking to exclude others, is usually a significant factor in determining legitimacy of expectation.48 Some expectations, the Court has held, are simply not among those that society is prepared to accept.49 In the context of norms for the use of rapidly evolving communications devices, the Court was reluctant to consider “the whole concept of privacy expectations” at all, preferring other decisional grounds: “The judiciary risks error by elaborating too fully on the Fourth Amendment implications of emerging technology before its role in society has become clear.”50

What seems to have emerged is a balancing standard that requires “an assessing of 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 the conduct as a technique of law enforcement.” Whereas Justice Harlan saw a greater need to restrain police officers through the warrant requirement as the intrusions on individual privacy grow more extensive,51 the Court’s solicitude for law enforcement objectives frequently tilts the balance in the other direction.

Application of this balancing test, because of the Court’s weighing of law enforcement investigative needs,52 and its subjective evaluation of privacy needs, has led to the creation of a two-tier or sliding-tier scale of privacy interests. The privacy test was originally designed to permit a determination that an interest protected by the Fourth Amendment had been invaded.53 If it had been, then ordinarily a warrant was required, subject only to the narrowly defined exceptions, and the scope of the search under those exceptions was “strictly tied to and justified by the circumstances which rendered its initiation permissible.”54 But the Court now uses the test to determine whether the interest invaded is important or persuasive enough so that a warrant is required to justify it;55 if the individual has a lesser expectation of privacy, then the invasion may be justified, absent a warrant, by the reasonableness of the intrusion.56 Exceptions to the warrant requirement are no longer evaluated solely by the justifications for the exception, e. g., exigent circumstances, and the scope of the search is no longer tied to and limited by the justification for the exception.57 The result has been a considerable expansion, beyond what existed prior to Katz, of the power of police and other authorities to conduct searches.

In United States v. Jones,58 the Court seemed to revitalize the significance of governmental trespass in determining whether a Fourth Amendment search has occurred. In Jones, the Court considered whether the attachment of a Global-Positioning-System (GPS) device to a car used by a suspected narcotics dealer and the monitoring of such device for twenty-eight days, constituted a search. Although the Court ruled unanimously that this month-long monitoring violated Jones’s rights, it splintered on the reasoning. A majority of the Court relied on the theory of common law trespass to find that the attachment of the device to the car represented a physical intrusion into Jones’s constitutionally protected “effect” or private property.59 While this holding obviated the need to assess the month-long tracking under Katz’s reasonable expectation of privacy test, five Justices, who concurred either with the majority opinion or concurred with the judgment, would have held that long-term GPS tracking can implicate an individual’s expectation of privacy.60 Some have read these concurrences as partly premised on the idea that while government access to a small data set—for example, one trip in a vehicle—might not violate one’s expectation of privacy, aggregating a month’s worth of personal data allows the government to create a “mosaic” about an individual’s personal life that violates that individual’s reasonable expectation of privacy.61 As a consequence, these concurring opinions could potentially have significant implications for the scope of the Fourth Amendment in relation to current and future technologies, such as cell phone tracking and wearable technologies that do not require a physical trespass to monitor a person’s activities and that can aggregate a wealth of personal data about users.62

30 See, e.g., California v. Hodari D., 499 U.S. 621, 626 (1991) (because there was no “seizure” of the defendant as he fled from police before being tackled, the drugs that he abandoned in flight could not be excluded as the fruits of an unreasonable seizure).

31 19 Howell’s State Trials 1029, 1035, 95 Eng. Reg. 807, 817–18 (1765).

32 Boyd v. United States, 116 U.S. 616, 627 (1886); Adams v. New York, 192 U.S. 585, 598 (1904).

33 Thus, the rule that “mere evidence” could not be seized but rather only the fruits of crime, its instrumentalities, or contraband, turned upon the question of the right of the public to possess the materials or the police power to make possession by the possessor unlawful. Gouled v. United States, 255 U.S. 298 (1921), overruled by Warden v. Hayden, 387 U.S. 294 (1967). See also Davis v. United States, 328 U.S. 582 (1946). Standing to contest unlawful searches and seizures was based upon property interests, United States v. Jeffers, 342 U.S. 48 (1951); Jones v. United States, 362 U.S. 257 (1960), as well as decision upon the validity of a consent to search. Chapman v. United States, 365 U.S. 610 (1961); Stoner v. California, 376 U.S. 483 (1964); Frazier v. Culp, 394 U.S. 731, 740 (1969).

34 277 U.S. 438 (1928). See also Goldman v. United States, 316 U.S. 129 (1942) (detectaphone placed against wall of adjoining room; no search and seizure).

35 Silverman v. United States, 365 U.S. 505 (1961) (spike mike pushed through a party wall until it hit a heating duct).

36 Warden v. Hayden, 387 U.S. 294, 304 (1967).

37 Katz v. United States, 389 U.S. 347, 353 (1967) (warrantless use of listening and recording device placed on outside of phone booth violates Fourth Amendment). See also Kyllo v. United States, 533 U.S. 27, 32–33 (2001) (holding presumptively unreasonable the warrantless use of a thermal imaging device to detect activity within a home by measuring heat outside the home, and noting that a contrary holding would permit developments in police technology “to erode the privacy guaranteed by the Fourth Amendment”.

38 389 U.S. at 353. Justice Harlan, concurring, formulated a two pronged test for determining whether the privacy interest is paramount: “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.’” Id. at 361.

39 389 U.S. at 351–52.

40 Mancusi v. DeForte, 392 U.S. 364, 368 (1968) (official had a reasonable expectation of privacy in an office he shared with others, although he owned neither the premises nor the papers seized). Minnesota v. Olson, 495 U.S. 91 (1990) (overnight guest in home has a reasonable expectation of privacy). But cf. Minnesota v. Carter, 525 U.S. 83 (1998) (a person present in someone else’s apartment for only a few hours for the purpose of bagging cocaine for later sale has no legitimate expectation of privacy); Cf. Rakas v. Illinois, 439 U.S. 128 (1978) (auto passengers demonstrated no legitimate expectation of privacy in glove compartment or under seat of auto). Property rights are still protected by the Amendment, however. A “seizure” of property can occur when there is some meaningful interference with an individual’s possessory interests in that property, and regardless of whether there is any interference with the individual’s privacy interest. Soldal v. Cook County, 506 U.S. 56 (1992) (a seizure occurred when sheriff’s deputies assisted in the disconnection and removal of a mobile home in the course of an eviction from a mobile home park). The reasonableness of a seizure, however, is an additional issue that may still hinge on privacy interests. United States v. Jacobsen, 466 U.S. 109, 120–21 (1984) (DEA agents reasonably seized package for examination after private mail carrier had opened the damaged package for inspection, discovered presence of contraband, and informed agents).

41 533 U.S. 27 (2001).

42 533 U.S. at 34.

43 Justice Harlan’s opinion has been much relied upon. See,e.g., Terry v. Ohio, 392 U.S. 1, 19 (1968); Rakas v. Illinois, 439 U.S. 128, 143–144 n.12 (1978); Smith v. Maryland, 442 U.S. 735, 740–41 (1979); United States v. Salvucci, 448 U.S. 83, 91–92 (1980); Rawlings v. Kentucky, 448 U.S. 98, 105–06 (1980); Bond v. United States, 529 U.S. 334, 338 (2000).

44 United States v. White, 401 U.S. 745, 786 (1971). See Smith v. Maryland, 442 U.S. 735, 740 n.5 (1979) (government could not condition “subjective expectations” by, say, announcing that henceforth all homes would be subject to warrantless entry, and thus destroy the “legitimate expectation of privacy”).

45 Rakas v. Illinois, 439 U.S. 128, 144 n.12 (1978).

46 E.g., Alderman v. United States, 394 U.S. 165 (1969); Mincey v. Arizona, 437 U.S. 385 (1978); Payton v. New York, 445 U.S. 573 (1980); Kyllo v. United States, 533 U.S. 27, 31 (2001).

47 E.g., United States v. Ross, 456 U.S. 798 (1982). See also Donovan v. Dewey, 452 U.S. 594 (1981) (commercial premises); Maryland v. Macon, 472 U.S. 463 (1985) (no legitimate expectation of privacy in denying to undercover officers allegedly obscene materials offered to public in bookstore).

48 E.g., United States v. Chadwick, 433 U.S. 1, 11 (1977); Katz v. United States, 389 U.S. 347, 352 (1967). But cf. South Dakota v. Opperman, 428 U.S. 364 (1976) (no legitimate expectation of privacy in automobile left with doors locked and windows rolled up). In Rawlings v. Kentucky, 448 U.S. 98 (1980), the fact that defendant had dumped a cache of drugs into his companion’s purse, having known her for only a few days and knowing others had access to the purse, was taken to establish that he had no legitimate expectation the purse would be free from intrusion.

49 E.g., United States v. Miller, 425 U.S. 435 (1976) (bank records); Smith v. Maryland, 442 U.S. 735 (1979) (numbers dialed from one’s telephone); Hudson v. Palmer, 468 U.S. 517 (1984) (prison cell); Illinois v. Andreas, 463 U.S. 765 (1983) (shipping container opened and inspected by customs agents and resealed and delivered to the addressee); California v. Greenwood, 486 U.S. 35 (1988) (garbage in sealed plastic bags left at curb for collection).

50 City of Ontario v. Quon, 560 U.S. ___, No. 08–1332, slip op. at 10 (2010) The Court cautioned that “[a] broad holding concerning employees’ privacy expectations vis-a-vis employer-provided technological equipment might have implications for future cases that cannot be predicted.” Id. at 11–12.

51 United States v. White, 401 U.S. 745, 786–87 (1971) (Justice Harlan dissenting).

52 E.g., Robbins v. California, 453 U.S. 420, 429, 433–34 (1981) (Justice Powell concurring), quoted with approval in United States v. Ross, 456 U.S. 798, 815–16 & n.21 (1982).

53 Katz v. United States, 389 U.S. 347, 351–52 (1967).

54 Terry v. Ohio, 392 U.S. 1, 19 (1968).

55 The prime example is the home, so that for entries either to search or to arrest, “the Fourth Amendment has drawn a firm line at the entrance to the house. Absent exigent circumstances, that threshold may not reasonably be crossed without a warrant.” Payton v. New York, 445 U.S. 573, 590 (1980); Steagald v. United States, 451 U.S. 204, 212 (1981); Kirk v. Louisiana, 536 U.S. 635 (2002) (per curiam). See also Mincey v. Arizona, 437 U.S. 385 (1978). Privacy in the home is not limited to intimate matters. “In the home all details are intimate details, because the entire area is held safe from prying government eyes.” Kyllo v. United States, 533 U.S. 27, 37 (2001).

56 One has a diminished expectation of privacy in automobiles. Arkansas v. Sanders, 442 U.S. 753, 761 (1979) (collecting cases); United States v. Ross, 456 U.S. 798, 804–09 (1982). A person’s expectation of privacy in personal luggage and other closed containers is substantially greater than in an automobile, United States v. Chadwick, 433 U.S. 1, 13 (1977); Arkansas v. Sanders, 442 U.S. 753 (1979), although, if the luggage or container is found in an automobile as to which there exists probable cause to search, the legitimate expectancy diminishes accordingly. United States v. Ross, supra. There is also a diminished expectation of privacy in a mobile home parked in a parking lot and licensed for vehicular travel. California v. Carney, 471 U.S. 386 (1985) (leaving open the question of whether the automobile exception also applies to a “mobile” home being used as a residence and not adapted for immediate vehicular use).

57 E.g., Texas v. White, 423 U.S. 67 (1975) (if probable cause to search automobile existed at scene, it can be removed to station and searched without warrant); United States v. Robinson, 414 U.S. 218 (1973) (once an arrest has been validly made, search pursuant thereto is so minimally intrusive in addition that scope of search is not limited by necessity of security of officer); United States v. Edwards, 415 U.S. 800 (1974) (incarcerated suspect; officers need no warrant to take his clothes for test because little additional intrusion). But see Ybarra v. Illinois, 444 U.S. 85 (1979) (officers on premises to execute search warrant of premises may not without more search persons found on premises).

58 565 U.S. ___, No. 10–1259, slip op. (2012).

59 Id. at 3–7. The physical trespass analysis was reprised in subsequent opinions. In its 2013 decision in Florida v. Jardines, the Court assessed whether a law enforcement officer had the legal authority to conduct a drug sniff with a trained canine on the front porch of a suspect’s home. Reviewing the law of trespass, the Court observed that visitors to a home, including the police, must have either explicit or implicit authority from the homeowner to enter upon and engage in various activities in the curtilage (i.e., the area immediately surrounding the home). Finding that the use of the dog to find incriminating evidence exceeded “background social norms” of what a visitor is normally permitted to do on another’s property, the Court held that the drug sniff constituted a search. 569 U.S. ___, No. 11–564, slip op. at 5–8 (2013). Similarly, in its 2015 per curiam opinion in Grady v. North Carolina, the Court emphasized the “physical intru[sion]” on a person when it found that attaching a device to a person’s body, without consent, for the purpose of tracking the person’s movements, constitutes a search within the meaning of the Fourth Amendment. 575 U.S. ___, No. 14–593, slip op. at 4–5 (2015). Neither the majority in Jardines nor the Court in Grady addressed whether the challenged conduct violates a reason-subject slip op. at 8–10.

60 Jones, slip op. at 14 (Alito, J., concurring in the judgment, joined by Ginsburg, Breyer, Kagan, JJ.) (concluding that respondent’s reasonable expectations of privacy were violated by the long-term monitoring of the movements of the respondent’s vehicle); id. at 3 (Sotomayor, J., concurring) (disagreeing with Justice Alito’s “approach” to the specific case but agreeing “longer term GPS monitoring in investigations of most offenses impinges on expectations of privacy.”).

61 See, e.g., United States v. Graham, 846 F.Supp. 2d 384, 394 (D. Md. 2012) (“It appears as though a five-Justice majority is willing to accept the principle that government surveillance over time can implicate an individual’s reasonable expectation of privacy.”), aff’d, ___ F.3d ___, No. 12–4659, slip op. at 31 (4th Cir. 2015); In re Application for Telephone Information Needed for a Criminal Investigation, 119 F. Supp. 3d. 1011, 1021–22 (N.D. Cal. 2015) (discussing the import of the two concurring opinions from Jones); United States v. Brooks, 911 F. Supp. 2d 836, 842 (D. Ariz. 2012) (noting that “[w]hile it does appear that in some future case, a five justice ‘majority’ is willing to accept the principle that Government surveillance can implicate an individual’s reasonable expectation of privacy over time, Jones does not dictate the result of the case at hand . . .”); but see United States v. Graham, ___ F.3d ___, No. 12–4659, 2016 WL 3068018, at *10 (4th Cir. May 31, 2016) (arguing that Justice Alito’s Jones concurrence should be read more narrowly so as to not implicate government access to information collected by third-party actors, no matter the quantity of information collected); In re Application of FBI, No. BR 14–01, 2014 WL 5463097, at *10 (FISA Ct. Mar. 20, 2014) (“While the concurring opinions in Jones may signal that some or even most of the Justices are ready to revisit certain settled Fourth Amendment principles, the decision in Jones itself breaks no new ground . . .”).

62 See generally Orin S. Kerr, The Mosaic Theory of the Fourth Amendment, 111 Mich. L. Rev. 311 (2012).