(Slip Opinion)              OCTOBER TERM, 2011                                       1

                                       Syllabus

         NOTE: Where it is feasible, a syllabus (headnote) will be released, as is
       being done in connection with this case, at the time the opinion is issued.
       The syllabus constitutes no part of the opinion of the Court but has been
       prepared by the Reporter of Decisions for the convenience of the reader.
       See United States v. Detroit Timber & Lumber Co., 200 U. S. 321, 337.


SUPREME COURT OF THE UNITED STATES

                                       Syllabus

                      UNITED STATES v. JONES

CERTIORARI TO THE UNITED STATES COURT OF APPEALS FOR
          THE DISTRICT OF COLUMBIA CIRCUIT

 No. 10–1259. Argued November 8, 2011—Decided January 23, 2012
The Government obtained a search warrant permitting it to install a
  Global-Positioning-System (GPS) tracking device on a vehicle regis-
  tered to respondent Jones’s wife. The warrant authorized installa-
  tion in the District of Columbia and within 10 days, but agents in-
  stalled the device on the 11th day and in Maryland. The Government
  then tracked the vehicle’s movements for 28 days. It subsequently
  secured an indictment of Jones and others on drug trafficking con-
  spiracy charges. The District Court suppressed the GPS data ob-
  tained while the vehicle was parked at Jones’s residence, but held the
  remaining data admissible because Jones had no reasonable expecta-
  tion of privacy when the vehicle was on public streets. Jones was
  convicted. The D. C. Circuit reversed, concluding that admission of
  the evidence obtained by warrantless use of the GPS device violated
  the Fourth Amendment.
Held: The Government’s attachment of the GPS device to the vehicle,
 and its use of that device to monitor the vehicle’s movements, consti-
 tutes a search under the Fourth Amendment. Pp. 3–12.
    (a) The Fourth Amendment protects the “right of the people to be
 secure in their persons, houses, papers, and effects, against unrea-
 sonable searches and seizures.” Here, the Government’s physical in-
 trusion on an “effect” for the purpose of obtaining information consti-
 tutes a “search.” This type of encroachment on an area enumerated
 in the Amendment would have been considered a search within the
 meaning of the Amendment at the time it was adopted. Pp. 3–4.
    (b) This conclusion is consistent with this Court’s Fourth Amend-
 ment jurisprudence, which until the latter half of the 20th century
 was tied to common-law trespass. Later cases, which have deviated
 from that exclusively property-based approach, have applied the
2                      UNITED STATES v. JONES

                                 Syllabus

    analysis of Justice Harlan’s concurrence in Katz v. United States, 389
    U. S. 347, which said that the Fourth Amendment protects a person’s
    “reasonable expectation of privacy,” id., at 360. Here, the Court need
    not address the Government’s contention that Jones had no “reason-
    able expectation of privacy,” because Jones’s Fourth Amendment
    rights do not rise or fall with the Katz formulation. At bottom, the
    Court must “assur[e] preservation of that degree of privacy against
    government that existed when the Fourth Amendment was adopted.”
    Kyllo v. United States, 533 U. S. 27, 34. Katz did not repudiate the
    understanding that the Fourth Amendment embodies a particular
    concern for government trespass upon the areas it enumerates. The
    Katz reasonable-expectation-of-privacy test has been added to, but
    not substituted for, the common-law trespassory test. See Alderman
    v. United States, 394 U. S. 165, 176; Soldal v. Cook County, 506 U. S.
    56, 64. United States v. Knotts, 460 U. S. 276, and United States v.
    Karo, 468 U. S. 705—post-Katz cases rejecting Fourth Amendment
    challenges to “beepers,” electronic tracking devices representing an-
    other form of electronic monitoring—do not foreclose the conclusion
    that a search occurred here. New York v. Class, 475 U. S. 106, and
    Oliver v. United States, 466 U. S. 170, also do not support the Gov-
    ernment’s position. Pp. 4–12.
       (c) The Government’s alternative argument—that if the attach-
    ment and use of the device was a search, it was a reasonable one—is
    forfeited because it was not raised below. P. 12.
615 F. 3d 544, affirmed.

   SCALIA, J., delivered the opinion of the Court, in which ROBERTS,
C. J., and KENNEDY, THOMAS, and SOTOMAYOR, JJ., joined. SOTOMAYOR,
J., filed a concurring opinion. ALITO, J., filed an opinion concurring in
the judgment, in which GINSBURG, BREYER, and KAGAN, JJ., joined.
                        Cite as: 565 U. S. ____ (2012)                              1

                             Opinion of the Court

     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, Wash-
     ington, D. C. 20543, of any typographical or other formal errors, in order
     that corrections may be made before the preliminary print goes to press.


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 individu-
al’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
2                   UNITED STATES v. JONES

                        Opinion of the Court

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 Govern-
ment 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 Gov-
ernment 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 distrib-
ute 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 automo-
bile 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 indict-
——————
  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).
                     Cite as: 565 U. S. ____ (2012)                   3

                         Opinion of the Court

ment, 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 ad-
mission 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.”

——————
  2 As we have noted, the Jeep was registered to Jones’s wife. The Gov-
ernment 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 Fourth Amendment objection, ibid., and the Govern-
ment has not challenged that determination here. We therefore do not
consider the Fourth Amendment significance of Jones’s status.
4                UNITED STATES v. JONES

                     Opinion of the Court

  It is important to be clear about what occurred in this
case: The Government physically occupied private proper-
ty 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 con-
nection 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 tres-
pass, 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.
                     Cite as: 565 U. S. ____ (2012)                     5

                          Opinion of the Court

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 offic-
ers 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 ex-
plained, for most of our history the Fourth Amendment
was understood to embody a particular concern for gov-
ernment trespass upon the areas (“persons, houses, pa-
pers, and effects”) it enumerates.3 Katz did not repudiate
——————
  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
6                    UNITED STATES v. JONES

                          Opinion of the Court

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 en-
forcement 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
——————
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 Fourth
Amendment. 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 conversa-
tions 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.
                      Cite as: 565 U. S. ____ (2012)                     7

                          Opinion of the Court

Amendment violations,” but did not “snuf[f ] out the previ-
ously 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 consti-
tutionally 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
——————
  5 The  concurrence notes that post-Katz we have explained that “ ‘an
actual trespass is neither necessary nor sufficient to establish a consti-
tutional violation.’ ” Post, at 6 (quoting United States v. Karo, 468 U. S.
705, 713 (1984)). That is undoubtedly true, and undoubtedly irrele-
vant. 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 Fourth Amendment 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.
8                    UNITED STATES v. JONES

                          Opinion of the Court

which we rejected Fourth Amendment challenges to
“beepers,” electronic tracking devices that represent an-
other 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 pri-
vacy 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 pub-
lic.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, per-
haps, 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
——————
  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.
                  Cite as: 565 U. S. ____ (2012)            9

                      Opinion of the Court

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 posses-
sion of the defendant until later. 468 U. S., at 708. Thus,
the specific question we considered was whether the in-
stallation “with the consent of the original owner consti-
tute[d] a search or seizure . . . when the container is deliv-
ered 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 conclu-
sion 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 contain-
er’s location. Cf. On Lee v. United States, 343 U. S. 747,
751–752 (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 state-
ment is of marginal relevance here since, as the Govern-
ment 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
10                   UNITED STATES v. JONES

                         Opinion of the Court

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
——————
  7 The  Government also points to Cardwell v. Lewis, 417 U. S. 583
(1974), 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 Fourth Amendment. 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 Fourth Amendment is concerned

with “any technical trespass that led to the gathering of evidence.”
Post, at 3 (ALITO, J., concurring in judgment) (emphasis added). The
Fourth Amendment 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.
                  Cite as: 565 U. S. ____ (2012)            11

                      Opinion of the Court

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 transmis-
sion 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 tres-
pass 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 exclusiv-
ity of the Katz test that needlessly leads us into “particu-
larly 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 thorough-
fares 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, multi-
ple vehicles, and perhaps aerial assistance,” post, at 12,
our cases suggest that such visual observation is constitu-
tionally 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
12               UNITED STATES v. JONES

                     Opinion of the Court

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 prece-
dent for the proposition that whether a search has oc-
curred depends on the nature of the crime being investi-
gated. 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 Amend-
ment 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., concur-
ring in denial of rehearing en banc). We consider the
argument forfeited. See Sprietsma v. Mercury Marine, 537
U. S. 51, 56, n. 4 (2002).
                     *  *     *
  The judgment of the Court of Appeals for the D. C.
Circuit is affirmed.
                                      It is so ordered.
                 Cite as: 565 U. S. ____ (2012)           1

                  SOTOMAYOR, J., concurring

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 Gov-
ernment 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 expecta-
tion 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
2                 UNITED STATES v. JONES

                   SOTOMAYOR, J., concurring

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 trespas-
sory test that preceded it. Ante, at 8. Thus, “when the
Government does engage in physical intrusion of a consti-
tutionally 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 constitu-
tional relevance of the Government’s physical intrusion on
Jones’ Jeep, erodes that longstanding protection for priva-
cy 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 track-
ing 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 sur-
veillance 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
                  Cite as: 565 U. S. ____ (2012)            3

                   SOTOMAYOR, J., concurring

would remain subject to Katz analysis.” Ante, at 11. As
JUSTICE ALITO incisively observes, the same technological
advances that have made possible nontrespassory surveil-
lance 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 na-
ture 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 meet-
ing, 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.” Illi-
nois v. Lidster, 540 U. S. 419, 426 (2004).
   Awareness that the Government may be watching chills
associational and expressive freedoms. And the Govern-
ment’s unrestrained power to assemble data that reveal
private aspects of identity is susceptible to abuse. The net
4                     UNITED STATES v. JONES

                       SOTOMAYOR, J., concurring

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 ex-
pect that their movements will be recorded and aggregat-
ed 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 ac-
companying trespass, is an unconstitutional invasion of
privacy”). I would also consider the appropriateness of
entrusting to the Executive, in the absence of any over-
sight 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).*
——————
   * 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 principles
may 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
                     Cite as: 565 U. S. ____ (2012)                   5

                      SOTOMAYOR, J., concurring

   More fundamentally, it may be necessary to reconsider
the premise that an individual has no reasonable expecta-
tion 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 Gov-
ernment 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

——————
Amendment implications of the installation of a beeper in a container
with the consent of the container’s original owner, who was aware
that 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 greeted
a 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 Govern-
ment’s surveillance. See 468 U. S., at 708–710. A car’s movements, by
contrast, are its owner’s movements.
6                UNITED STATES v. JONES

                  SOTOMAYOR, J., concurring

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 constitu-
tionally 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.
                     Cite as: 565 U. S. ____ (2012)                    1

                   ALITO, J., concurring in judgment

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 device1 to the under-
side of the vehicle that respondent drove, the law enforce-
ment 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.

——————
  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) (here-
inafter Prosser & Keeton). Here, there was no actual damage to the
vehicle to which the GPS device was attached.
2                 UNITED STATES v. JONES

                ALITO, J., concurring in judgment

  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
                    Cite as: 565 U. S. ____ (2012)                   3

                   ALITO, J., concurring in judgment

accepts the holding in United States v. Knotts, 460 U. S.
276 (1983), that the use of a surreptitiously planted elec-
tronic 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 tres-
pass followed by the gathering of evidence constitutes a

——————
  3The 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                 UNITED STATES v. JONES

                ALITO, J., concurring in judgment

search. In the early electronic surveillance cases, the
Court concluded that a Fourth Amendment search oc-
curred 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 overhear-
ing 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 prohibit-
ing “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
                 Cite as: 565 U. S. ____ (2012)            5

                ALITO, J., concurring in judgment

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 signifi-
cance,” 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 decou-
pled 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] justifi-
ably relied while using the telephone booth.” Katz, supra,
6                 UNITED STATES v. JONES

                ALITO, J., concurring in judgment

at 353.
  Under this approach, as the Court later put it when
addressing the relevance of a technical trespass, “an actu-
al trespass is neither necessary nor sufficient to establish
a constitutional violation.” United States v. Karo, 468
U. S. 705, 713 (1984) (emphasis added). Ibid. (“Com-
par[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 con-
    trol the right of the Government to search and seize
    has been discredited.’ Katz, 389 U. S., at 353, (quot-
    ing 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 tech-
nical 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 Amend-
ment 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
                  Cite as: 565 U. S. ____ (2012)             7

                ALITO, J., concurring in judgment

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., concur-
ring) (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 dissent-
ing 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 reason-
ing 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 prop-
erty not actionable); D. Dobbs, Law of Torts 124 (2000)
(same). But under the Court’s reasoning, this conduct
8                         UNITED STATES v. JONES

                        ALITO, J., concurring in judgment

may violate the Fourth Amendment. By contrast, if long-
term monitoring can be accomplished without committing
a technical trespass—suppose, for example, that the Fed-
eral Government required or persuaded auto manufactur-
ers 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 regis-
tered, 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 re-
spondent “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
State4 or a State that has adopted the Uniform Marital


——————
    4 See,   e.g., Cal. Family Code Ann. §760 (West 2004).
                      Cite as: 565 U. S. ____ (2012)                9

                    ALITO, J., concurring in judgment

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 (Se-
cond) of Torts §217 and Comment e (1963 and 1964);
Dobbs, supra, at 123. In recent years, courts have wres-
tled 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 com-
puter 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 tres-
pass as it existed at the time of the adoption of the Fourth

——————
 5 See   Uniform Marital Property Act §4, 9A U. L. A. 116 (1998).
10                   UNITED STATES v. JONES

                   ALITO, J., concurring in judgment

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 as-
sumption 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 sig-
nificant 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 develop-
ment 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 hap-
pened with respect to wiretapping. After Katz, Congress

——————
  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.
                    Cite as: 565 U. S. ____ (2012)                11

                  ALITO, J., concurring in judgment

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 move-
ments. In some locales, closed-circuit television video
monitoring is becoming ubiquitous. On toll roads, auto-
matic 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 devic-
es 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

——————
   7 See Kerr, The Fourth Amendment and New Technologies: Constitu-

tional 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.
12                   UNITED STATES v. JONES

                   ALITO, J., concurring in judgment

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 (“crowdsourc-
ing”) 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 under-
taken. 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 investi-
gation of unusual importance could have justified such an


——————
  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, 460 U. S. 276 (1983), or United States v. Karo, 468 U. S. 705
(1984), 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.
                 Cite as: 565 U. S. ____ (2012)          13

                ALITO, J., concurring in judgment

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 situ-
ated to gauge changing public attitudes, to draw detailed
lines, and to balance privacy and public safety in a com-
prehensive way.
   To date, however, Congress and most States have not
enacted statutes regulating the use of GPS tracking tech-
nology 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 rea-
sonable 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 cata-
logue every single movement of an individual’s car for
a very long period. In this case, for four weeks, law en-
forcement agents tracked every movement that respond-
ent 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
14                   UNITED STATES v. JONES

                   ALITO, J., concurring in judgment

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 avail-
able techniques.
                        *    *     *
   For these reasons, I conclude that the lengthy monitor-
ing that occurred in this case constituted a search under
the Fourth Amendment. I therefore agree with the major-
ity that the decision of the Court of Appeals must be
affirmed.




——————
  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 18 U. S. C. §3117(a) and Rule 41(b)(4). In the
courts below the Government did not argue, and has not argued here,
that the Fourth Amendment does not impose these precise restrictions
and that the violation of these restrictions does not demand the sup-
pression 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.
