NOTICE: This opinion is subject to
formal revision before publication in the preliminary print of the
United States Reports. Readers are requested to notify the Reporter
of Decisions, Supreme Court of the United States, Washington,
D. C. 20543, of any typographical or other formal errors, in
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															SUPREME COURT OF THE UNITED STATES

															_________________

															No. 10–1259

															_________________

															UNITED STATES, PETITIONER v. ANTOINE JONES

															on writ of certiorari to the united states
court of appeals for the district of columbia circuit

															[January 23, 2012]

															     Justice Scalia
delivered the opinion of the Court.

															     We decide whether the
attachment of a Global-Positioning-System (GPS) tracking device to
an individual’s vehicle, and subsequent use of that device to
monitor the vehicle’s movements on public streets, constitutes a
search or seizure within the meaning of the Fourth Amendment.

															I

															     In 2004 respondent
Antoine Jones, owner and operator of a nightclub in the District of
Columbia, came under suspicion of trafficking in narcotics and was
made the target of an investigation by a joint FBI and Metropolitan
Police Department task force. Officers employed various
investigative techniques, including visual surveillance of the
nightclub, installation of a camera focused on the front door of
the club, and a pen register and wiretap covering Jones’s cellular
phone.

															     Based in part on
information gathered from these sources, in 2005 the Government
applied to the United States District Court for the District of
Columbia for a warrant authorizing the use of an electronic
tracking device on the Jeep Grand Cherokee registered to Jones’s
wife. A warrant issued, authorizing installation of the de- vice in
the District of Columbia and within 10 days.

															     On the 11th day, and
not in the District of Columbia but in Maryland, [ 1 ] agents installed a GPS tracking device on
the undercarriage of the Jeep while it was parked in a public
parking lot. Over the next 28 days, the Government used the device
to track the vehicle’s movements, and once had to replace the
device’s battery when the vehicle was parked in a different public
lot in Maryland. By means of signals from multiple satellites, the
device established the vehicle’s location within 50 to 100 feet,
and communicated that location by cellular phone to a Government
computer. It relayed more than 2,000 pages of data over the 4-week
period.

															     The Government
ultimately obtained a multiple-count indictment charging Jones and
several alleged co-conspirators with, as relevant here, conspiracy
to distribute and possess with intent to distribute five kilograms
or more of cocaine and 50 grams or more of cocaine base, in
violation of 21 U. S. C. §§841 and 846. Before trial,
Jones filed a motion to suppress evidence obtained through the GPS
device. The District Court granted the motion only in part,
suppressing the data obtained while the vehicle was parked in the
garage adjoining Jones’s residence. 451 F. Supp. 2d 71, 88
(2006). It held the remaining data admissible, because “ ‘[a]
person traveling in an automobile on public thoroughfares has no
reasonable expectation of privacy in his movements from one place
to another.’ ” Ibid. (quoting United States v. Knotts, 460
U. S. 276, 281 (1983) ). Jones’s trial in October 2006
produced a hung jury on the conspiracy count.

															     In March 2007, a grand
jury returned another indictment, charging Jones and others with
the same conspir- acy. The Government introduced at trial the same
GPS-derived locational data admitted in the first trial, which
connected Jones to the alleged conspirators’ stash house that
contained $850,000 in cash, 97 kilograms of cocaine, and 1 kilogram
of cocaine base. The jury returned a guilty verdict, and the
District Court sentenced Jones to life imprisonment.

															     The United States Court
of Appeals for the District of Columbia Circuit reversed the
conviction because of admission of the evidence obtained by
warrantless use of the GPS device which, it said, violated the
Fourth Amend- ment. United States v. Maynard, 615 F. 3d 544
(2010). The D. C. Circuit denied the Government’s petition for
rehearing en banc, with four judges dissenting. 625 F. 3d 766
(2010). We granted certiorari, 564 U. S. ___ (2011).

															II

															A

															     The Fourth Amendment
provides in relevant part that “[t]he right of the people to be
secure in their persons, houses, papers, and effects, against
unreasonable searches and seizures, shall not be violated.” It is
beyond dispute that a vehicle is an “effect” as that term is used
in the Amendment. United States v. Chadwick, 433 U. S. 1, 12
(1977) . We hold that the Government’s installation of a GPS device
on a target’s vehicle, [ 2 ]
and its use of that device to monitor the vehicle’s movements,
constitutes a “search.”

															     It is important to be
clear about what occurred in this case: The Government physically
occupied private property for the purpose of obtaining information.
We have no doubt that such a physical intrusion would have been
considered a “search” within the meaning of the Fourth Amendment
when it was adopted. Entick v. Carrington, 95 Eng. Rep. 807
(C. P. 1765), is a “case we have described as a ‘monument of
English freedom’ ‘undoubtedly familiar’ to ‘every American
statesman’ at the time the Constitution was adopted, and considered
to be ‘the true and ultimate expression of constitutional
law’ ” with regard to search and seizure. Brower v. County of
Inyo, 489 U. S. 593, 596 (1989) (quoting Boyd v. United
States, 116 U. S. 616, 626 (1886) ). In that case, Lord Camden
expressed in plain terms the significance of property rights in
search-and-seizure analysis:

															“[O]ur law holds the property of every man
so sacred, that no man can set his foot upon his neighbour’s close
without his leave; if he does he is a trespasser, though he does no
damage at all; if he will tread upon his neighbour’s ground, he
must justify it by law.” Entick, supra, at 817.

															The text of the Fourth Amendment reflects its
close connection to property, since otherwise it would have
referred simply to “the right of the people to be secure against
unreasonable searches and seizures”; the phrase “in their persons,
houses, papers, and effects” would have been superfluous.

															     Consistent with this
understanding, our Fourth Amendment jurisprudence was tied to
common-law trespass, at least until the latter half of the 20th
century. Kyllo v. United States, 533 U. S. 27, 31 (2001) ;
Kerr, The Fourth Amendment and New Technologies: Constitutional
Myths and the Case for Caution, 102 Mich. L. Rev. 801, 816
(2004). Thus, in Olmstead v. United States, 277 U. S. 438
(1928) , we held that wiretaps attached to telephone wires on the
public streets did not constitute a Fourth Amendment search because
“[t]here was no entry of the houses or offices of the defendants,”
id., at 464.

															     Our later cases, of
course, have deviated from that exclusively property-based
approach. In Katz v. United States, 389 U. S. 347, 351 (1967)
, we said that “the Fourth Amendment protects people, not places,”
and found a violation in attachment of an eavesdropping device to a
public telephone booth. Our later cases have applied the analysis
of Justice Harlan’s concurrence in that case, which said that a
violation occurs when government officers violate a person’s
“reasonable expectation of privacy,” id., at 360. See, e.g., Bond
v. United States, 529 U. S. 334 (2000) ; California v.
Ciraolo, 476 U. S. 207 (1986) ; Smith v. Maryland, 442
U. S. 735 (1979) .

															     The Government contends
that the Harlan standard shows that no search occurred here, since
Jones had no “reasonable expectation of privacy” in the area of the
Jeep accessed by Government agents (its underbody) and in the
locations of the Jeep on the public roads, which were visible to
all. But we need not address the Government’s contentions, because
Jones’s Fourth Amendment rights do not rise or fall with the Katz
formulation. At bottom, we must “assur[e] preservation of that
degree of privacy against government that existed when the Fourth
Amendment was adopted.” Kyllo, supra, at 34. As explained, for most
of our history the Fourth Amendment was understood to embody a
particular concern for government trespass upon the areas
(“persons, houses, papers, and effects”) it enumerates. [ 3 ] Katz did not repudiate that
understanding. Less than two years later the Court upheld
defendants’ contention that the Government could not introduce
against them conversations between other people obtained by
warrantless placement of electronic surveillance devices in their
homes. The opinion rejected the dissent’s contention that there was
no Fourth Amendment violation “unless the conversational privacy of
the homeowner himself is invaded.” [ 4 ] Alderman v. United States, 394 U. S. 165, 176
(1969) . “[W]e [do not] believe that Katz, by holding that the
Fourth Amendment protects persons and their private conversations,
was intended to withdraw any of the protection which the Amendment
extends to the home . . . .” Id., at 180.

															     More recently, in
Soldal v. Cook County, 506 U. S. 56 (1992) , the Court
unanimously rejected the argument that although a “seizure” had
occurred “in a ‘technical’ sense” when a trailer home was forcibly
removed, id., at 62, no Fourth Amendment violation occurred because
law enforcement had not “invade[d] the [individuals’] privacy,”
id., at 60. Katz, the Court explained, established that “property
rights are not the sole measure of Fourth Amendment violations,”
but did not “snuf[f] out the previously recognized protection for
property.” 506 U. S., at 64. As Justice Brennan explained in
his concurrence in Knotts, Katz did not erode the principle “that,
when the Government does engage in physical intrusion of a
constitutionally protected area in order to obtain information,
that intrusion may constitute a violation of the Fourth Amendment.”
460 U. S., at 286 (opinion concurring in judgment). We have
embodied that preservation of past rights in our very definition of
“reasonable expectation of privacy” which we have said to be an
expectation “that has 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.”
Minnesota v. Carter, 525 U. S. 83, 88 (1998) (internal
quotation marks omitted). Katz did not narrow the Fourth
Amendment’s scope. [ 5 ]

															     The Government contends
that several of our post-Katz cases foreclose the conclusion that
what occurred here constituted a search. It relies principally on
two cases in which we rejected Fourth Amendment challenges to
“beepers,” electronic tracking devices that represent another form
of electronic monitoring. The first case, Knotts, upheld against
Fourth Amendment challenge the use of a “beeper” that had been
placed in a container of chloroform, allowing law enforcement to
monitor the location of the container. 460 U. S., at 278. We
said that there had been no infringement of Knotts’ reasonable
expectation of privacy since the information obtained—the location
of the automobile carrying the container on public roads, and the
location of the off-loaded container in open fields near Knotts’
cabin—had been voluntarily conveyed to the public. [ 6 ] Id., at 281–282. But as we have
discussed, the Katz reasonable-expectation-of-privacy test has been
added to, not substituted for, the common-law trespassory test. The
holding in Knotts addressed only the former, since the latter was
not at issue. The beeper had been placed in the container before it
came into Knotts’ possession, with the consent of the then-owner.
460 U. S., at 278. Knotts did not challenge that installation,
and we specifically de- clined to consider its effect on the Fourth
Amendment analysis. Id., at 279, n. Knotts would be relevant,
perhaps, if the Government were making the argument that what would
otherwise be an unconstitutional search is not such where it
produces only public information. The Government does not make that
argument, and we know of no case that would support it.

															     The second “beeper”
case, United States v. Karo, 468 U. S. 705 (1984) , does not
suggest a different conclusion. There we addressed the question
left open by Knotts, whether the installation of a beeper in a
container amounted to a search or seizure. 468 U. S., at 713.
As in Knotts, at the time the beeper was installed the container
belonged to a third party, and it did not come into possession of
the defendant until later. 468 U. S., at 708. Thus, the
specific question we considered was whether the installation “with
the consent of the original owner constitute[d] a search or seizure
. . . when the container is delivered to a buyer having
no knowledge of the presence of the beeper.” Id., at 707 (emphasis
added). We held not. The Government, we said, came into physical
contact with the container only before it belonged to the defendant
Karo; and the transfer of the container with the unmonitored beeper
inside did not convey any information and thus did not invade
Karo’s privacy. See id., at 712. That conclusion is perfectly
consistent with the one we reach here. Karo accepted the container
as it came to him, beeper and all, and was therefore not entitled
to object to the beeper’s presence, even though it was used to
monitor the container’s location. Cf. On Lee v. United States, 343
U. S. 747 –752 (1952) (no search or seizure where an
informant, who was wearing a concealed microphone, was invited into
the defendant’s business). Jones, who possessed the Jeep at the
time the Government trespassorily inserted the
information-gathering device, is on much different footing.

															     The Government also
points to our exposition in New York v. Class, 475 U. S. 106
(1986) , that “[t]he exterior of a car . . . is thrust
into the public eye, and thus to examine it does not constitute a
‘search.’ ” Id., at 114. That statement is of marginal
relevance here since, as the Government acknowledges, “the officers
in this case did more than conduct a visual inspection of
respondent’s vehicle,” Brief for United States 41 (emphasis added).
By attaching the device to the Jeep, officers encroached on a
protected area. In Class itself we suggested that this would make a
difference, for we concluded that an officer’s momentary reaching
into the interior of a vehicle did constitute a search. [ 7 ] 475 U. S., at 114–115.

															     Finally, the
Government’s position gains little support from our conclusion in
Oliver v. United States, 466 U. S. 170 (1984) , that officers’
information-gathering intrusion on an “open field” did not
constitute a Fourth Amendment search even though it was a trespass
at common law, id., at 183. Quite simply, an open field, unlike the
curtilage of a home, see United States v. Dunn, 480 U. S. 294,
300 (1987) , is not one of those protected areas enumerated in the
Fourth Amendment. Oliver, supra, at 176–177. See also Hester v.
United States, 265 U. S. 57, 59 (1924) . The Government’s
physical intrusion on such an area—unlike its intrusion on the
“effect” at issue here—is of no Fourth Amendment significance. [ 8 ]

															B

															     The concurrence
begins by accusing us of applying “18th-century tort law.” Post, at
1. That is a distortion. What we apply is an 18th-century guarantee
against un- reasonable searches, which we believe must provide at
a minimum the degree of protection it afforded when it was
adopted. The concurrence does not share that belief. It would apply
exclusively Katz’s reasonable-expectation-of-privacy test, even
when that eliminates rights that previously existed.

															     The concurrence faults
our approach for “present[ing] particularly vexing problems” in
cases that do not involve physical contact, such as those that
involve the transmission of electronic signals. Post, at 9. We
entirely fail to understand that point. For unlike the concurrence,
which would make Katz the exclusive test, we do not make trespass
the exclusive test. Situations involving merely the transmission of
electronic signals without trespass would remain subject to Katz
analysis.

															     In fact, it is the
concurrence’s insistence on the exclusivity of the Katz test that
needlessly leads us into “particularly vexing problems” in the
present case. This Court has to date not deviated from the
understanding that mere visual observation does not constitute a
search. See Kyllo, 533 U. S., at 31–32. We accordingly held in
Knotts that “[a] person traveling in an automobile on public
thoroughfares has no reasonable expectation of privacy in his
movements from one place to another.” 460 U. S., at 281. Thus,
even assuming that the concurrence is correct to say that
“[t]raditional surveillance” of Jones for a 4-week period “would
have required a large team of agents, multiple vehicles, and
perhaps aerial assistance,” post, at 12, our cases suggest that
such visual observation is constitutionally permissible. It may be
that achieving the same result through electronic means, without an
accompany- ing trespass, is an unconstitutional invasion of
privacy, but the present case does not require us to answer that
question.

															     And answering it
affirmatively leads us needlessly into additional thorny problems.
The concurrence posits that “relatively short-term monitoring of a
person’s movements on public streets” is okay, but that “the use of
longer term GPS monitoring in investigations of most offenses” is
no good. Post, at 13 (emphasis added). That introduces yet another
novelty into our jurisprudence. There is no precedent for the
proposition that whether a search has occurred depends on the
nature of the crime being investigated. And even accepting that
novelty, it remains unexplained why a 4-week investigation is
“surely” too long and why a drug-trafficking conspiracy involving
sub- stantial amounts of cash and narcotics is not an “extra-
ordinary offens[e]” which may permit longer observation. See post,
at 13–14. What of a 2-day monitoring of a suspected purveyor of
stolen electronics? Or of a 6-month monitoring of a suspected
terrorist? We may have to grapple with these “vexing problems” in
some future case where a classic trespassory search is not involved
and resort must be had to Katz analysis; but there is no reason for
rushing forward to resolve them here.

															III

															     The Government argues
in the alternative that even if the attachment and use of the
device was a search, it was reasonable—and thus lawful—under the
Fourth Amendment because “officers had reasonable suspicion, and
in- deed probable cause, to believe that [Jones] was a leader in a
large-scale cocaine distribution conspiracy.” Brief for United
States 50–51. We have no occasion to consider this argument. The
Government did not raise it below, and the D. C. Circuit
therefore did not address it. See 625 F. 3d, at 767 (Ginsburg,
Tatel, and Griffith, JJ., concurring in denial of rehearing en
banc). We consider the argument forfeited. See Sprietsma v. Mercury
Marine, 537 U. S. 51 , n. 4 (2002).

															*  *  *

															     The judgment of the
Court of Appeals for the D. C. Circuit is affirmed.

															It is so ordered. Notes 1 In this litigation, the
Government has conceded noncompliance with the warrant and has
argued only that a warrant was not required. United States v.
Maynard, 615 F. 3d 544, 566, n. (CADC 2010). 2 As we have noted, the
Jeep was registered to Jones’s wife. The Government acknowledged,
however, that Jones was “the exclusive driver.” Id., at 555, n.
(internal quotation marks omitted). If Jones was not the owner he
had at least the property rights of a bailee. The Court of Appeals
concluded that the vehicle’s registration did not affect his
ability to make a objection, ibid., and the Government has not
challenged that determination here. We therefore do not consider
the significance of Jones’s status. 3 Justice Alito’s
concurrence (hereinafter concurrence) doubts the wisdom of our
approach because “it is almost impossible to think of
late-18th-century situations that are analogous to what took place
in this case.” Post, at 3 (opinion concurring in judgment). But in
fact it posits a situation that is not far afield—a constable’s
concealing himself in the target’s coach in order to track its
movements. Ibid. There is no doubt that the information gained by
that trespassory activity would be the product of an unlawful
search—whether that information consisted of the conversations
occurring in the coach, or of the destinations to which the coach
traveled. In any case, it is quite irrelevant whether there was an
18th-century analog. Whatever new methods of investigation may be
devised, our task, at a minimum, is to decide whether the action in
question would have constituted a “search” within the original
meaning of the . Where, as here, the Government obtains information
by physically intruding on a constitutionally protected area, such
a search has undoubtedly occurred. 4 Thus, the concurrence’s
attempt to recast Alderman as meaning that individuals have a
“legitimate expectation of privacy in all conversations that [take]
place under their roof,” post, at 6–7, is foreclosed by the Court’s
opinion. The Court took as a given that the homeowner’s
“conversational privacy” had not been violated. 5 The concurrence notes
that post-Katz we have explained that “ ‘an actual trespass is
neither necessary nor sufficient to establish a constitutional
violation.’ ” Post, at 6 (quoting United States v. Karo, ).
That is undoubtedly true, and undoubtedly irrelevant. Karo was
considering whether a seizure occurred, and as the concurrence
explains, a seizure of property occurs, not when there is a
trespass, but “when there is some meaningful interference with an
individual’s possessory interests in that property.” Post, at 2
(internal quotation marks omitted). Likewise with a search.
Trespass alone does not qualify, but there must be conjoined with
that what was present here: an attempt to find something or to
obtain information. Related to this, and similarly irrelevant, is
the concurrence’s point that, if analyzed separately, neither the
installation of the device nor its use would constitute a search.
See ibid. Of course not. A trespass on “houses” or “effects,” or a
Katz invasion of privacy, is not alone a search unless it is done
to obtain information; and the obtaining of information is not
alone a search unless it is achieved by such a trespass or invasion
of privacy. 6 Knotts noted the “limited
use which the government made of the signals from this particular
beeper,” 460 U. S., at 284; and reserved the question whether
“different constitutional principles may be applicable” to
“dragnet-type law enforcement practices” of the type that GPS
tracking made possible here, ibid. 7 The Government also
points to Cardwell v. Lewis, , in which the Court rejected the
claim that the inspection of an impounded vehicle’s tire tread and
the collection of paint scrapings from its exterior violated the .
Whether the plural-ity said so because no search occurred or
because the search was rea-sonable is unclear. Compare id., at 591
(opinion of Blackmun, J.) (“[W]e fail to comprehend what
expectation of privacy was infringed”), with id., at 592 (“Under
circumstances such as these, where probable cause exists, a
warrantless examination of the exterior of a car is not
unreasonable . . . ”). 8 Thus, our theory is not
that the is concerned with “any technical trespass that led to the
gathering of evidence.” Post, at 3 (Alito, J., concurring in
judgment) (emphasis added). The protects against trespassory
searches only with regard to those items (“persons, houses, papers,
and effects”) that it enumerates. The trespass that occurred in
Oliver may properly be understood as a “search,” but not one “in
the constitutional sense.” 466 U. S., at 170,
183. SUPREME COURT OF THE UNITED STATES

															_________________

															No. 10–1259

															_________________

															UNITED STATES, PETITIONER v. ANTOINE JONES

															on writ of certiorari to the united states
court of appeals for the district of columbia circuit

															[January 23, 2012]

															     Justice Alito, with
whom Justice Ginsburg, Justice Breyer, and Justice Kagan join,
concurring in the judgment.

															     This case requires us
to apply the Fourth Amendment’s prohibition of unreasonable
searches and seizures to a 21st-century surveillance technique, the
use of a Global Po-sitioning System (GPS) device to monitor a
vehicle’s move-ments for an extended period of time. Ironically,
the Court has chosen to decide this case based on 18th-century tort
law. By attaching a small GPS device [ 1 ] to the underside of the vehicle that respondent drove,
the law enforcement officers in this case engaged in conduct that
might have provided grounds in 1791 for a suit for trespass to
chattels. [ 2 ] And for this
reason, the Court concludes, the installation and use of the GPS
device constituted a search. Ante, at 3–4.

															     This holding, in my
judgment, is unwise. It strains the language of the Fourth
Amendment; it has little if any support in current Fourth Amendment
case law; and it is highly artificial.

															     I would analyze the
question presented in this case by asking whether respondent’s
reasonable expectations of privacy were violated by the long-term
monitoring of the movements of the vehicle he drove.

															I

															A

															     The Fourth Amendment
prohibits “unreasonable searches and seizures,” and the Court makes
very little effort to explain how the attachment or use of the GPS
device fits within these terms. The Court does not contend that
there was a seizure. A seizure of property occurs when there is
“some meaningful interference with an in-dividual’s possessory
interests in that property,” United States v. Jacobsen, 466
U. S. 109, 113 (1984) , and here there was none. Indeed, the
success of the surveillance technique that the officers employed
was dependent on the fact that the GPS did not interfere in any way
with the operation of the vehicle, for if any such interference had
been detected, the device might have been discovered.

															     The Court does claim
that the installation and use of the GPS constituted a search, see
ante, at 3–4, but this con-clusion is dependent on the questionable
proposition that these two procedures cannot be separated for
purposes of Fourth Amendment analysis. If these two procedures are
analyzed separately, it is not at all clear from the Court’s
opinion why either should be regarded as a search. It is clear that
the attachment of the GPS device was not itself a search; if the
device had not functioned or if the officers had not used it, no
information would have been obtained. And the Court does not
contend that the use of the device constituted a search either. On
the contrary, the Court accepts the holding in United States v.
Knotts, 460 U. S. 276 (1983) , that the use of a
surreptitiously planted electronic device to monitor a vehicle’s
movements on public roads did not amount to a search. See ante, at
7.

															     The Court argues—and I
agree—that “we must ‘assur[e] preservation of that degree of
privacy against government that existed when the Fourth Amendment
was adopted.’ ” Ante, at 5 (quoting Kyllo v. United States,
533 U. S. 27 , 34 (2001)). But it is almost impossible to
think of late- 18th-century situations that are analogous to what
took place in this case. (Is it possible to imagine a case in which
a constable secreted himself somewhere in a coach and remained
there for a period of time in order to monitor the movements of the
coach’s owner? [ 3 ] ) The
Court’s theory seems to be that the concept of a search, as
originally un-derstood, comprehended any technical trespass that
led to the gathering of evidence, but we know that this is
in-correct. At common law, any unauthorized intrusion on private
property was actionable, see Prosser & Keeton 75, but a
trespass on open fields, as opposed to the “curtilage” of a home,
does not fall within the scope of the Fourth Amendment because
private property outside the curtilage is not part of a “hous[e]”
within the meaning of the Fourth Amendment. See Oliver v. United
States, 466 U. S. 170 (1984) ; Hester v. United States, 265
U. S. 57 (1924) .

															B

															     The Court’s reasoning
in this case is very similar to that in the Court’s early decisions
involving wiretapping and electronic eavesdropping, namely, that a
technical trespass followed by the gathering of evidence
constitutes a search. In the early electronic surveillance cases,
the Court concluded that a Fourth Amendment search occurred when
private conversations were monitored as a result of an
“unauthorized physical penetration into the premises occupied” by
the defendant. Silverman v. United States, 365 U. S. 505, 509
(1961) . In Silverman, police officers listened to conversations in
an attached home by inserting a “spike mike” through the wall that
this house shared with the vacant house next door. Id., at 506.
This procedure was held to be a search because the mike made
contact with a heating duct on the other side of the wall and thus
“usurp[ed] . . . an integral part of the premises.” Id.,
at 511.

															     By contrast, in cases
in which there was no trespass, it was held that there was no
search. Thus, in Olmstead v. United States, 277 U. S. 438
(1928) , the Court found that the Fourth Amendment did not apply
because “[t]he taps from house lines were made in the streets near
the houses.” Id., at 457. Similarly, the Court concluded that no
search occurred in Goldman v. United States, 316 U. S. 129,
135 (1942) , where a “detectaphone” was placed on the outer wall of
defendant’s office for the purpose of overhearing conversations
held within the room.

															     This trespass-based
rule was repeatedly criticized. In Olmstead, Justice Brandeis wrote
that it was “immaterial where the physical connection with the
telephone wires was made.” 277 U. S., at 479 (dissenting
opinion). Al-though a private conversation transmitted by wire did
not fall within the literal words of the Fourth Amendment, he
argued, the Amendment should be understood as prohibiting “every
unjustifiable intrusion by the government upon the privacy of the
individual.” Id., at 478. See also, e.g., Silverman, supra, at 513
(Douglas, J., concurring) (“The concept of ‘an unauthorized
physical penetration into the premises,’ on which the present
decision rests seems to me beside the point. Was not the wrong
. . . done when the intimacies of the home were tapped,
recorded, or revealed? The depth of the penetration of the
electronic device—even the degree of its remoteness from the inside
of the house—is not the measure of the injury”); Goldman, supra, at
139 (Murphy, J., dissenting) (“[T]he search of one’s home or office
no longer requires physical entry, for science has brought forth
far more effective devices for the invasion of a person’s privacy
than the direct and obvious methods of oppression which were
detested by our forebears and which inspired the Fourth
Amendment”).

															     Katz v. United States,
389 U. S. 347 (1967) , finally did away with the old approach,
holding that a trespass was not required for a Fourth Amendment
violation. Katz in-volved the use of a listening device that was
attached to the outside of a public telephone booth and that
allowed police officers to eavesdrop on one end of the target’s
phone conversation. This procedure did not physically intrude on
the area occupied by the target, but the Katz Court,
“repudiate[ed]” the old doctrine, Rakas v. Illinois, 439 U. S.
128, 143 (1978) , and held that “[t]he fact that the electronic
device employed . . . did not happen to penetrate the
wall of the booth can have no constitutional significance,” 389
U. S., at 353 (“[T]he reach of th[e] [Fourth] Amendment cannot
turn upon the presence or absence of a physical intrusion into any
given enclosure”); see Rakas, supra, at 143 (describing Katz as
holding that the “ca-pacity to claim the protection for the Fourth
Amendment depends not upon a property right in the invaded place
but upon whether the person who claims the protection of the
Amendment has a legitimate expectation of privacy in the invaded
place”); Kyllo, supra, at 32 (“We have since decoupled violation of
a person’s Fourth Amendment rights from trespassory violation of
his property”). What mattered, the Court now held, was whether the
conduct at issue “violated the privacy upon which [the defendant]
justifiably relied while using the telephone booth.” Katz, supra,
at 353.

															     Under this approach, as
the Court later put it when addressing the relevance of a technical
trespass, “an actual trespass is neither necessary nor sufficient
to establish a constitutional violation.” United States v. Karo,
468 U. S. 705, 713 (1984) (emphasis added). Ibid.
(“Compar[ing] Katz v. United States, 389 U. S. 347 (1967) (no
trespass, but Fourth Amendment violation), with Oliver v. United
States, 466 U. S. 170 (1984) (trespass, but no Fourth
Amendment violation)”). In Oliver, the Court wrote:

															“The existence of a property right is but
one element in determining whether expectations of privacy are
legitimate. ‘The premise that property interests control the right
of the Government to search and seize has been discredited.’ Katz,
389 U. S., at 353, (quoting Warden v. Hayden, 387 U. S.
294, 304 (1967) ; some internal quotation marks omitted).” 466
U. S., at 183.

															II

															     The majority suggests
that two post-Katz decisions—Soldal v. Cook County, 506 U. S.
56 (1992) , and Alderman v. United States, 394 U. S. 165
(1969) —show that a technical trespass is sufficient to establish
the existence of a search, but they provide little support.

															     In Soldal, the Court
held that towing away a trailer home without the owner’s consent
constituted a seizure even if this did not invade the occupants’
personal privacy. But in the present case, the Court does not find
that there was a seizure, and it is clear that none occurred.

															     In Alderman, the Court
held that the Fourth Amendment rights of homeowners were implicated
by the use of a surreptitiously planted listening device to monitor
third-party conversations that occurred within their home. See 394
U. S., at 176–180. Alderman is best understood to mean that
the homeowners had a legitimate expectation of privacy in all
conversations that took place under their roof. See Rakas, 439
U. S., at 144, n. 12 (citing Alderman for the proposition that
“the Court has not altogether abandoned use of property concepts in
determining the presence or absence of the privacy interests
protected by that Amendment”); 439 U. S., at 153 (Powell, J.,
concurring) (citing Alderman for the proposition that “property
rights reflect society’s explicit recognition of a person’s
au-thority to act as he wishes in certain areas, and there- fore
should be considered in determining whether an individual’s
expectations of privacy are reasonable); Karo, supra, at 732
(Stevens, J., concurring in part and dissenting in part) (citing
Alderman in support of the proposition that “a homeowner has a
reasonable expectation of privacy in the contents of his home,
including items owned by others”).

															     In sum, the majority is
hard pressed to find support in post-Katz cases for its
trespass-based theory.

															III

															     Disharmony with a
substantial body of existing case law is only one of the problems
with the Court’s approach in this case.

															     I will briefly note
four others. First, the Court’s reasoning largely disregards what
is really important (the use of a GPS for the purpose of long-term
tracking) and instead attaches great significance to something that
most would view as relatively minor (attaching to the bottom of a
car a small, light object that does not interfere in any way with
the car’s operation). Attaching such an object is generally
regarded as so trivial that it does not provide a basis for
recovery under modern tort law. See Prosser & Keeton §14, at 87
(harmless or trivial contact with personal property not
actionable); D. Dobbs, Law of Torts 124 (2000) (same). But under
the Court’s reasoning, this conduct may violate the Fourth
Amendment. By contrast, if long-term monitoring can be accomplished
without committing a technical trespass—suppose, for example, that
the Federal Government required or persuaded auto manufacturers to
include a GPS tracking device in every car—the Court’s theory would
provide no protection.

															     Second, the Court’s
approach leads to incongruous results. If the police attach a GPS
device to a car and use the device to follow the car for even a
brief time, under the Court’s theory, the Fourth Amendment applies.
But if the police follow the same car for a much longer period
using unmarked cars and aerial assistance, this tracking is not
subject to any Fourth Amendment constraints.

															     In the present case,
the Fourth Amendment applies, the Court concludes, because the
officers installed the GPS device after respondent’s wife, to whom
the car was registered, turned it over to respondent for his
exclusive use. See ante, at 8. But if the GPS had been attached
prior to that time, the Court’s theory would lead to a different
result. The Court proceeds on the assumption that respondent “had
at least the property rights of a bailee,” ante, at 3, n. 2, but a
bailee may sue for a trespass to chattel only if the injury occurs
during the term of the bailment. See 8A Am. Jur. 2d, Bailment §166,
pp. 685–686 (2009). So if the GPS device had been installed
before respondent’s wife gave him the keys, respondent would have
no claim for trespass—and, presumably, no Fourth Amendment claim
either.

															     Third, under the
Court’s theory, the coverage of the Fourth Amendment may vary from
State to State. If the events at issue here had occurred in a
community property State [ 4 ]
or a State that has adopted the Uniform Marital Property Act, [ 5 ] respondent would likely be
an owner of the vehicle, and it would not matter whether the GPS
was installed before or after his wife turned over the keys. In
non-community-property States, on the other hand, the registration
of the vehicle in the name of respondent’s wife would generally be
regarded as presumptive evidence that she was the sole owner. See
60 C. J. S., Motor Vehicles §231, pp. 398–399
(2002); 8 Am. Jur. 2d, Automobiles §1208, pp. 859–860
(2007).

															     Fourth, the Court’s
reliance on the law of trespass will present particularly vexing
problems in cases involving surveillance that is carried out by
making electronic, as opposed to physical, contact with the item to
be tracked. For example, suppose that the officers in the present
case had followed respondent by surreptitiously activating a stolen
vehicle detection system that came with the car when it was
purchased. Would the sending of a radio signal to activate this
system constitute a trespass to chattels? Trespass to chattels has
traditionally required a physical touching of the property. See
Restatement (Second) of Torts §217 and Comment e (1963 and 1964);
Dobbs, supra, at 123. In recent years, courts have wrestled with
the application of this old tort in cases involving unwanted
electronic contact with computer systems, and some have held that
even the transmission of electrons that occurs when a communication
is sent from one computer to another is enough. See, e.g.,
CompuServe, Inc. v. Cyber Promotions, Inc. 962 F. Supp. 1015, 1021
(SD Ohio 1997); Thrifty-Tel, Inc. v. Bezenek, 46 Cal. App. 4th
1559, 1566, n. 6 (1996). But may such decisions be followed in
applying the Court’s trespass theory? Assuming that what matters
under the Court’s theory is the law of trespass as it existed at
the time of the adoption of the Fourth Amendment, do these recent
decisions represent a change in the law or simply the application
of the old tort to new situations?

															IV

															A

															     The Katz
expectation-of-privacy test avoids the problems and complications
noted above, but it is not without its own difficulties. It
involves a degree of circularity, see Kyllo, 533 U. S., at 34,
and judges are apt to confuse their own expectations of privacy
with those of the hypothetical reasonable person to which the Katz
test looks. See Minnesota v. Carter, 525 U. S. 83, 97 (1998)
(Scalia, J., concurring). In addition, the Katz test rests on the
assumption that this hypothetical reasonable person has a
well-developed and stable set of privacy expectations. But
technology can change those expectations. Dramatic technological
change may lead to periods in which popular expectations are in
flux and may ultimately produce significant changes in popular
attitudes. New technology may provide increased convenience or
security at the expense of privacy, and many people may find the
tradeoff worthwhile. And even if the public does not welcome the
diminution of privacy that new technology entails, they may
eventually reconcile themselves to this development as inevitable.
[ 6 ]

															     On the other hand,
concern about new intrusions on privacy may spur the enactment of
legislation to protect against these intrusions. This is what
ultimately happened with respect to wiretapping. After Katz,
Congress did not leave it to the courts to develop a body of Fourth
Amendment case law governing that complex subject. Instead,
Congress promptly enacted a comprehensive statute, see 18
U. S. C. §§2510–2522 (2006 ed. and Supp. IV), and since
that time, the regulation of wiretapping has been governed
primarily by statute and not by case law. [ 7 ] In an ironic sense, although Katz overruled
Olmstead, Chief Justice Taft’s suggestion in the latter case that
the regulation of wiretapping was a matter better left for
Congress, see 277 U. S., at 465–466, has been borne out.

															B

															     Recent years have
seen the emergence of many new devices that permit the monitoring
of a person’s movements. In some locales, closed-circuit television
video monitoring is becoming ubiquitous. On toll roads, automatic
toll collection systems create a precise record of the movements of
motorists who choose to make use of that convenience. Many
motorists purchase cars that are equipped with devices that permit
a central station to ascertain the car’s location at any time so
that roadside assistance may be provided if needed and the car may
be found if it is stolen.

															     Perhaps most
significant, cell phones and other wireless devices now permit
wireless carriers to track and record the location of users—and as
of June 2011, it has been reported, there were more than 322
million wireless devices in use in the United States. [ 8 ] For older phones, the accuracy of
the location information depends on the den-sity of the tower
network, but new “smart phones,” which are equipped with a GPS
device, permit more precise tracking. For example, when a user
activates the GPS on such a phone, a provider is able to monitor
the phone’s location and speed of movement and can then report back
real-time traffic conditions after combining (“crowdsourcing”) the
speed of all such phones on any particular road. [ 9 ] Similarly, phone-location-tracking
services are offered as “social” tools, allowing consumers to find
(or to avoid) others who enroll in these services. The availability
and use of these and other new devices will continue to shape the
average person’s expectations about the privacy of his or her daily
movements.

															V

															     In the pre-computer
age, the greatest protections of privacy were neither
constitutional nor statutory, but practical. Traditional
surveillance for any extended period of time was difficult and
costly and therefore rarely undertaken. The surveillance at issue
in this case—constant monitoring of the location of a vehicle for
four weeks—would have required a large team of agents, multiple
vehicles, and perhaps aerial assistance. [ 10 ] Only an investigation of unusual importance
could have justified such an expenditure of law enforcement
resources. Devices like the one used in the present case, however,
make long-term monitoring relatively easy and cheap. In
circumstances involving dramatic technological change, the best
solution to privacy concerns may be legislative. See, e.g., Kerr,
102 Mich. L. Rev., at 805–806. A legislative body is well situated
to gauge changing public attitudes, to draw detailed lines, and to
balance privacy and public safety in a comprehensive way.

															     To date, however,
Congress and most States have not enacted statutes regulating the
use of GPS tracking technology for law enforcement purposes. The
best that we can do in this case is to apply existing Fourth
Amendment doctrine and to ask whether the use of GPS tracking in a
particular case involved a degree of intrusion that a reasonable
person would not have anticipated.

															     Under this approach,
relatively short-term monitoring of a person’s movements on public
streets accords with expectations of privacy that our society has
recognized as reasonable. See Knotts, 460 U. S., at 281–282.
But the use of longer term GPS monitoring in investigations of most
offenses impinges on expectations of privacy. For such offenses,
society’s expectation has been that law enforcement agents and
others would not—and indeed, in the main, simply could not—secretly
monitor and catalogue every single movement of an individual’s car
for a very long period. In this case, for four weeks, law
enforcement agents tracked every movement that respondent made in
the vehicle he was driving. We need not identify with precision the
point at which the tracking of this vehicle became a search, for
the line was surely crossed before the 4-week mark. Other cases may
present more difficult questions. But where uncertainty exists with
respect to whether a certain period of GPS surveil lance is long
enough to constitute a Fourth Amendment search, the police may
always seek a warrant. [ 11 ] We also need not consider whether prolonged GPS monitoring in the
context of investigations involving extraordinary offenses would
similarly intrude on a constitutionally protected sphere of
privacy. In such cases, long-term tracking might have been mounted
using previously available techniques.

															*  *  *

															     For these reasons, I
conclude that the lengthy monitoring that occurred in this case
constituted a search under the Fourth Amendment. I therefore agree
with the majority that the decision of the Court of Appeals must be
affirmed. Notes 1 Although the record does
not reveal the size or weight of the device used in this case,
there is now a device in use that weighs two ounces and is the size
of a credit card. Tr. of Oral Arg. 27. 2 At common law, a suit for
trespass to chattels could be maintained if there was a violation
of “the dignitary interest in the inviolability of chattels,” but
today there must be “some actual damage to the chattel before the
action can be maintained.” W. Keeton, D. Dobbs, R. Keeton, & D.
Owen, Prosser & Keeton on Law of Torts 87 (5th ed. 1984)
(hereinafter Prosser & Keeton). Here, there was no actual
damage to the vehicle to which the GPS device was
attached. 3 The Court suggests that
something like this might have occurred in 1791, but this would
have required either a gigantic coach, a very tiny constable, or
both—not to mention a constable with incredible fortitude and
patience. 4 See, e.g., Cal. Family
Code Ann. §760 (West 2004). 5 See Uniform Marital
Property Act §4, 9A U. L. A. 116 (1998). 6 See, e.g., NPR, The End
of Privacy http://www.npr.org/series/114250076/the-end-of-privacy
(all Internet materials as visited Jan. 20, 2012, and
available in Clerk of Court’s case file); Time Magazine, Everything
About You Is Being Tracked—Get Over It, Joel Stein, Mar. 21, 2011,
Vol. 177, No. 11. 7 See Kerr, The and New
Technologies: Constitutional Myths and the Case for Caution, 102
Mich. L. Rev. 801, 850–851 (2004) (hereinafter Kerr). 8 See CTIA Consumer Info,
50 Wireless Quick Facts,
http://www.ctia.org/consumer_info/index.cfm/AID/10323. 9 See, e.g., The bright
side of sitting in traffic: Crowdsourcing road congestion data,
Google Blog,
http://googleblog.blogspot.com/2009/08/bright-side-of-sitting-in-traffic.html. 10 Even
with a radio transmitter like those used in United States v.
Knotts, , or United States v. Karo, , such long-term surveillance
would have been exceptionally demanding. The beepers used in those
cases merely “emit[ted] periodic signals that [could] be picked up
by a radio receiver.” Knotts, 460 U.S., at 277. The signal had a
limited range and could be lost if the police did not stay close
enough. Indeed, in Knotts itself, officers lost the signal from the
beeper, and only “with the assistance of a monitoring device
located in a helicopter [was] the approximate location of the
signal . . . picked up again about one hour later.” Id.,
at 278. 11 In
this case, the agents obtained a warrant, but they did not comply
with two of the warrant’s restrictions: They did not install the
GPS device within the 10-day period required by the terms of the
warrant and by Fed. Rule Crim. Proc. 41(e)(2)(B)(i), and they did
not install the GPS device within the District of Columbia, as
required by the terms of the warrant and by and Rule 41(b)(4). In
the courts below the Government did not argue, and has not argued
here, that the does not impose these precise restrictions and that
the violation of these restrictions does not demand the suppression
of evidence obtained using the tracking device. See, e.g., United
States v. Gerber, 994 F. 2d 1556, 1559–1560 (CA11 1993);
United States v. Burke, 517 F. 2d 377, 386–387 (CA2 1975).
Because it was not raised, that question is not before
us. SUPREME COURT OF THE UNITED STATES

															_________________

															No. 10–1259

															_________________

															UNITED STATES, PETITIONER v. ANTOINE
JONES

															on writ of certiorari to the united states
court of appeals for the district of columbia circuit

															[January 23, 2012]

															Justice Sotomayor, concurring.

															I join the Court’s opinion because I agree that
a search within the meaning of the Fourth Amendment occurs, at a
minimum, “[w]here, as here, the Government obtains information by
physically intruding on a constitutionally protected area.” Ante, at 6, n. 3. In this case, the Government
installed a Global Positioning System (GPS) tracking device on
respondent Antoine Jones’ Jeep without a valid warrant and without
Jones’ consent, then used that device to monitor the Jeep’s
movements over the course of four weeks. The Government usurped
Jones’ property for the purpose of conducting surveillance on him,
thereby invading privacy interests long afforded, and undoubtedly
entitled to, Fourth Amendment protection. See, e.g., Silverman v. United States , 365
U.S. 505 , 511–512 (1961).

															Of course, the Fourth Amendment is not concerned
only with trespassory intrusions on property. See, e.g., Kyllo v. United States , 533 U.S.
27 , 31–33 (2001). Rather, even in the absence of a trespass, “a
Fourth Amendment search occurs when the government violates a
subjective expectation of privacy that society recognizes as
reasonable.” Id., at 33; see also Smith v. Maryland , 442 U.S.
735 , 740–741 (1979); Katz v. United States , 389 U.S.
347 , 361 (1967) (Harlan, J., concurring). In Katz , this
Court enlarged its then-prevailing focus on property rights by
announcing that the reach of the Fourth Amendment does not “turn
upon the presence or absence of a physical intrusion.” Id., at 353. As the majority’s opinion makes clear, however, Katz ’s reasonable-expectation-of-privacy test augmented, but
did not displace or diminish, the common-law trespassory test that
preceded it. Ante, at 8. Thus, “when the Government does engage in physical intrusion of a constitutionally
protected area in order to obtain information, that intrusion may
constitute a violation of the Fourth Amendment.” United
States v. Knotts , 460
U.S. 276 , 286 (1983) (Brennan, J., concurring in judgment); see
also, e.g., Rakas v. Illinois , 439 U.S.
128 , 144, n. 12 (1978). Justice Alito’s approach, which
discounts altogether the constitutional relevance of the
Government’s physical intrusion on Jones’ Jeep, erodes that
longstanding protection for privacy expectations inherent in items
of property that people possess or control. See post, at 5–7
(opinion concurring in judgment). By contrast, the trespassory test
applied in the majority’s opinion reflects an irreducible
constitutional minimum: When the Government physically invades
personal property to gather information, a search occurs. The
reaffirmation of that principle suffices to decide this case.

															Nonetheless, as Justice Alito notes, physical
intrusion is now unnecessary to many forms of surveillance. Post, at 9–12. With increasing regularity, the Government
will be capable of duplicating the monitoring undertaken in this
case by enlisting factory- or owner-installed vehicle tracking
devices or GPS-enabled smartphones. See United States v. Pineda-Moreno , 617 F.3d 1120, 1125 (CA9 2010) (Kozinski,
C. J., dissenting from denial of rehearing en banc). In cases
of electronic or other novel modes of surveillance that do not
depend upon a physical invasion on property, the majority opinion’s
trespassory test may provide little guidance. But “[s]ituations
involving merely the transmission of electronic signals without
trespass would remain subject to Katz analysis.” Ante, at 11. As Justice Alito incisively observes, the same
technological advances that have made possible nontrespassory
surveillance techniques will also affect the Katz test by
shaping the evolution of societal privacy expectations. Post, at 10–11. Under that rubric, I agree with Justice
Alito that, at the very least, “longer term GPS monitoring in
inves- tigations of most offenses impinges on expectations of
privacy.” Post, at 13.

															In cases involving even short-term monitoring,
some unique attributes of GPS surveillance relevant to the Katz analysis will require particular attention. GPS
monitoring generates a precise, comprehensive record of a person’s
public movements that reflects a wealth of detail about her
familial, political, professional, religious, and sexual
associations. See, e.g., People v. Weaver , 12
N.Y.3d 433, 441–442, 909 N.E.2d 1195, 1199 (2009) (“Disclosed in
[GPS] data . . . will be trips the indisputably private
nature of which takes little imagination to conjure: trips to the
psychiatrist, the plastic surgeon, the abortion clinic, the AIDS
treatment center, the strip club, the criminal defense attorney,
the by-the-hour motel, the union meeting, the mosque, synagogue or
church, the gay bar and on and on”). The Government can store such
records and efficiently mine them for information years into the
future. Pineda-Moreno , 617 F. 3d, at 1124 (opinion of
Kozinski, C. J.). And because GPS monitoring is cheap in
comparison to conventional surveillance techniques and, by design,
proceeds surreptitiously, it evades the ordinary checks that
constrain abusive law enforcement practices: “limited police
resources and community hostility.” Illinois v. Lidster , 540 U.S.
419 , 426 (2004).

															Awareness that the Government may be watching
chills associational and expressive freedoms. And the Government’s
unrestrained power to assemble data that reveal private aspects of
identity is susceptible to abuse. The net result is that GPS
monitoring—by making available at a relatively low cost such a
substantial quantum of intimate information about any person whom
the Government, in its unfettered discretion, chooses to track—may
“alter the relationship between citizen and government in a way
that is inimical to democratic society.” United States v. Cuevas-Perez , 640 F.3d 272, 285 (CA7 2011) (Flaum, J.,
concurring).

															I would take these attributes of GPS monitoring
into account when considering the existence of a reasonable
societal expectation of privacy in the sum of one’s public
movements. I would ask whether people reasonably expect that their
movements will be recorded and aggregated in a manner that enables
the Government to ascertain, more or less at will, their political
and religious beliefs, sexual habits, and so on. I do not regard as
dispositive the fact that the Government might obtain the fruits of
GPS monitoring through lawful conventional surveillance techniques.
See Kyllo , 533 U. S., at 35, n. 2; ante, at
11 (leaving open the possibility that duplicating traditional
surveillance “through electronic means, without an accompanying
trespass, is an unconstitutional invasion of privacy”). I would
also consider the appropriateness of entrusting to the Executive,
in the absence of any oversight from a coordinate branch, a tool so
amenable to misuse, especially in light of the Fourth Amendment’s
goal to curb arbitrary exercises of police power to and prevent “a
too permeating police surveillance,” United States v. Di
Re , 332 U.S.
581 , 595 (1948).[ 1 ]*

															More fundamentally, it may be necessary to
reconsider the premise that an individual has no reasonable
expectation of privacy in information voluntarily disclosed to
third parties. E.g., Smith , 442 U. S., at 742; United States v. Miller , 425
U.S. 435 , 443 (1976). This approach is ill suited to the
digital age, in which people reveal a great deal of information
about themselves to third parties in the course of carrying out
mundane tasks. People disclose the phone numbers that they dial or
text to their cellu- lar providers; the URLs that they visit and
the e-mail addresses with which they correspond to their Internet
service providers; and the books, groceries, and medi- cations they
purchase to online retailers. Perhaps, as Justice Alito notes, some
people may find the “tradeoff ” of privacy for convenience
“worthwhile,” or come to accept this “diminution of privacy” as
“inevitable,” post, at 10, and perhaps not. I for one doubt
that people would accept without complaint the warrantless
disclosure to the Government of a list of every Web site they had
visited in the last week, or month, or year. But whatever the
societal expectations, they can attain constitutionally protected
status only if our Fourth Amendment jurisprudence ceases to treat
secrecy as a prerequisite for privacy. I would not assume that all
information voluntarily disclosed to some member of the public for
a limited purpose is, for that reason alone, disentitled to Fourth
Amendment protection. See Smith , 442 U. S., at 749
(Marshall, J., dissenting) (“Privacy is not a discrete commodity,
possessed absolutely or not at all. Those who disclose certain
facts to a bank or phone company for a limited business purpose
need not assume that this information will be released to other
persons for other purposes”); see also Katz , 389 U. S.,
at 351–352 (“[W]hat [a person] seeks to preserve as private, even
in an area accessible to the public, may be constitutionally
protected”).

															Resolution of these difficult questions in this
case is unnecessary, however, because the Government’s physical
intrusion on Jones’ Jeep supplies a narrower basis for decision. I
therefore join the majority’s opinion. Notes 1 * United States v. Knotts , 460 U.S.
276 (1983), does not foreclose the conclusion that GPS
monitoring, in the absence of a physical intrusion, is a Fourth
Amendment search. As the majority’s opinion notes, Knotts reserved the question whether “ ‘different constitutional
principlesmay be applicable’ ” to invasive law enforcement
practices such as GPS tracking. See ante, at 8, n. 6
(quoting 460 U. S., at 284). United States v. Karo , 468 U.S.
705 (1984), addressed the Fourth Amendment implications of the
installation of a beeper in a container with the consent of the
container’s original owner, who was awarethat the beeper would be
used for surveillance purposes. Id., at 707. Owners of
GPS-equipped cars and smartphones do not contemplate that these
devices will be used to enable covert surveillance of their
movements. To the contrary, subscribers of one such service
greeteda similar suggestion with anger. Quain, Changes to OnStar’s
Privacy Terms Rile Some Users, N. Y. Times (Sept. 22, 2011),
online at
http://wheels.blogs.nytimes.com/2011/09/22/changes-to-onstars-privacy-terms-rile-some-users
(as visited Jan. 19, 2012, and available in Clerk of Court’s case
file). In addition, the bugged container in Karo lacked the
close relationship with the target that a car shares with its
owner. The bugged container in Karo was stationary for much
of the Government’s surveillance. See 468 U. S., at 708–710. A
car’s movements, by contrast, are its owner’s
movements.