`(Slip Opinion)
`
`OCTOBER TERM, 2017
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`
`Syllabus
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`
`1
`
` 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.
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`
`
` The syllabus constitutes no part of the opinion of the Court but has been
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` prepared by the Reporter of Decisions for the convenience of the reader.
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` See United States v. Detroit Timber & Lumber Co., 200 U. S. 321, 337.
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`
`SUPREME COURT OF THE UNITED STATES
`
`
`
` Syllabus
`
` CARPENTER v. UNITED STATES
`
`CERTIORARI TO THE UNITED STATES COURT OF APPEALS FOR
`
`THE SIXTH CIRCUIT
` No. 16–402. Argued November 29, 2017—Decided June 22, 2018
`
`Cell phones perform their wide and growing variety of functions by con-
`
`tinuously connecting to a set of radio antennas called “cell sites.”
`
`Each time a phone connects to a cell site, it generates a time-stamped
`record known as cell-site location information (CSLI). Wireless carri-
`
`ers collect and store this information for their own business purposes.
`Here, after the FBI identified the cell phone numbers of several rob-
`
`bery suspects, prosecutors were granted court orders to obtain the
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`
`suspects’ cell phone records under the Stored Communications Act.
`
`Wireless carriers produced CSLI for petitioner Timothy Carpenter’s
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`phone, and the Government was able to obtain 12,898 location points
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`cataloging Carpenter’s movements over 127 days—an average of 101
`
`data points per day. Carpenter moved to suppress the data, arguing
`
`that the Government’s seizure of the records without obtaining a
`warrant supported by probable cause violated the Fourth Amend-
`
`ment. The District Court denied the motion, and prosecutors used
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`the records at trial to show that Carpenter’s phone was near four of
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`the robbery locations at the time those robberies occurred. Carpen-
`ter was convicted. The Sixth Circuit affirmed, holding that Carpen-
`ter lacked a reasonable expectation of privacy in the location infor-
`
`mation collected by the FBI because he had shared that information
`
`with his wireless carriers.
`Held:
`
`
`
`1. The Government’s acquisition of Carpenter’s cell-site records
`
`
`was a Fourth Amendment search. Pp. 4–18.
`
`
`
`
`(a) The Fourth Amendment protects not only property interests
`
`but certain expectations of privacy as well. Katz v. United States, 389
`U. S. 347, 351. Thus, when an individual “seeks to preserve some-
`
`
`thing as private,” and his expectation of privacy is “one that society is
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`

`

`2
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`CARPENTER v. UNITED STATES
`
`
`Syllabus
`
`prepared to recognize as reasonable,” official intrusion into that
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`sphere generally qualifies as a search and requires a warrant sup-
`
`ported by probable cause. Smith v. Maryland, 442 U. S. 735, 740 (in-
`ternal quotation marks and alterations omitted). The analysis re-
`garding which expectations of privacy are entitled to protection is
`informed by historical understandings “of what was deemed an un-
`reasonable search and seizure when [the Fourth Amendment] was
`adopted.” Carroll v. United States, 267 U. S. 132, 149. These Found-
`ing-era understandings continue to inform this Court when applying
`the Fourth Amendment to innovations in surveillance tools. See, e.g.,
`
`
`Kyllo v. United States, 533 U. S. 27. Pp. 4–7.
`
`
`
`(b) The digital data at issue—personal location information
`maintained by a third party—does not fit neatly under existing prec-
`
`edents but lies at the intersection of two lines of cases. One set ad-
`
`dresses a person’s expectation of privacy in his physical location and
`
`movements. See, e.g., United States v. Jones, 565 U. S. 400 (five Jus-
`
`tices concluding that privacy concerns would be raised by GPS track-
`ing). The other addresses a person’s expectation of privacy in infor-
`mation voluntarily turned over to third parties. See United States v.
`
`Miller, 425 U. S. 435 (no expectation of privacy in financial records
`held by a bank), and Smith, 442 U. S. 735 (no expectation of privacy
`in records of dialed telephone numbers conveyed to telephone compa-
`ny). Pp. 7–10.
`
`
`
`(c) Tracking a person’s past movements through CSLI partakes
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`of many of the qualities of GPS monitoring considered in Jones—it is
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`detailed, encyclopedic, and effortlessly compiled. At the same time,
`however, the fact that the individual continuously reveals his loca-
`
`tion to his wireless carrier implicates the third-party principle of
`
`
`Smith and Miller. Given the unique nature of cell-site records, this
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`Court declines to extend Smith and Miller to cover them. Pp. 10–18.
`
`
`
`(1) A majority of the Court has already recognized that indi-
`
`viduals have a reasonable expectation of privacy in the whole of their
`physical movements. Allowing government access to cell-site rec-
`ords—which “hold for many Americans the ‘privacies of life,’ ” Riley v.
`
`
`California, 573 U. S. ___, ___—contravenes that expectation. In fact,
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`historical cell-site records present even greater privacy concerns than
`
`
`the GPS monitoring considered in Jones: They give the Government
`near perfect surveillance and allow it to travel back in time to retrace
`a person’s whereabouts, subject only to the five-year retention poli-
`cies of most wireless carriers. The Government contends that CSLI
`data is less precise than GPS information, but it thought the data ac-
`curate enough here to highlight it during closing argument in Car-
`penter’s trial. At any rate, the rule the Court adopts “must take ac-
`
`count of more sophisticated systems that are already in use or in
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`

`

`3
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`Cite as: 585 U. S. ____ (2018)
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`
`Syllabus
`
`development,” Kyllo, 533 U. S., at 36, and the accuracy of CSLI is
`rapidly approaching GPS-level precision. Pp. 12–15.
`(2) The Government contends that the third-party doctrine
`governs this case, because cell-site records, like the records in Smith
`and Miller, are “business records,” created and maintained by wire-
`
`
`less carriers. But there is a world of difference between the limited
`
`types of personal information addressed in Smith and Miller and the
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`exhaustive chronicle of location information casually collected by
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`wireless carriers.
`
`The third-party doctrine partly stems from the notion that an indi-
`vidual has a reduced expectation of privacy in information knowingly
`
`shared with another. Smith and Miller, however, did not rely solely
`
`on the act of sharing. They also considered “the nature of the partic-
`ular documents sought” and limitations on any “legitimate ‘expecta-
`
`tion of privacy’ concerning their contents.” Miller, 425 U. S., at 442.
`
`In mechanically applying the third-party doctrine to this case the
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`Government fails to appreciate the lack of comparable limitations on
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`the revealing nature of CSLI.
`
`Nor does the second rationale for the third-party doctrine—
`voluntary exposure—hold up when it comes to CSLI. Cell phone lo-
`
`cation information is not truly “shared” as the term is normally un-
`derstood. First, cell phones and the services they provide are “such a
`
`pervasive and insistent part of daily life” that carrying one is indis-
`pensable to participation in modern society. Riley, 573 U. S., at ___.
`
`
`Second, a cell phone logs a cell-site record by dint of its operation,
`
`without any affirmative act on the user’s part beyond powering up.
`Pp. 15–17.
`
`
`
`(d) This decision is narrow. It does not express a view on matters
`not before the Court; does not disturb the application of Smith and
`Miller or call into question conventional surveillance techniques and
`
`tools, such as security cameras; does not address other business rec-
`ords that might incidentally reveal location information; and does not
`consider other collection techniques involving foreign affairs or na-
`tional security. Pp. 17–18.
`
`2. The Government did not obtain a warrant supported by proba-
`ble cause before acquiring Carpenter’s cell-site records. It acquired
`those records pursuant to a court order under the Stored Communi-
`
`cations Act, which required the Government to show “reasonable
`grounds” for believing that the records were “relevant and material to
`
`an ongoing investigation.” 18 U. S. C. §2703(d). That showing falls
`well short of the probable cause required for a warrant. Consequent-
`
`ly, an order issued under §2703(d) is not a permissible mechanism for
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`accessing historical cell-site records. Not all orders compelling the
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`production of documents will require a showing of probable cause. A
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`

`4
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` CARPENTER v. UNITED STATES
`
`
`Syllabus
`warrant is required only in the rare case where the suspect has a le-
`gitimate privacy interest in records held by a third party. And even
`
` though the Government will generally need a warrant to access
`
`CSLI, case-specific exceptions—e.g., exigent circumstances—may
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`support a warrantless search. Pp. 18–22.
` 819 F. 3d 880, reversed and remanded.
`ROBERTS, C. J., delivered the opinion of the Court, in which GINS-
`
`
`BURG, BREYER, SOTOMAYOR, and KAGAN, JJ., joined. KENNEDY, J., filed a
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`
`
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`dissenting opinion, in which THOMAS and ALITO, JJ., joined. THOMAS, J.,
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`
`
`
`
`filed a dissenting opinion. ALITO, J., filed a dissenting opinion, in which
`THOMAS, J., joined. GORSUCH, J., filed a dissenting opinion.
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`

`

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` Cite as: 585 U. S. ____ (2018)
`
`Opinion of the Court
`
`1
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` NOTICE: This opinion is subject to formal revision before publication in the
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`
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` preliminary print of the United States Reports. Readers are requested to
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` notify the Reporter of Decisions, Supreme Court of the United States, Wash-
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` ington, D. C. 20543, of any typographical or other formal errors, in order
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` that corrections may be made before the preliminary print goes to press.
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`SUPREME COURT OF THE UNITED STATES
`
`
`
`_________________
`
` No. 16–402
`_________________
` TIMOTHY IVORY CARPENTER, PETITIONER v.
`
`
` UNITED STATES
`
`ON WRIT OF CERTIORARI TO THE UNITED STATES COURT OF
`
`
`APPEALS FOR THE SIXTH CIRCUIT
`
`[June 22, 2018]
`
`CHIEF JUSTICE ROBERTS delivered the opinion of the
`Court.
`
`This case presents the question whether the Govern-
`
`ment conducts a search under the Fourth Amendment
`when it accesses historical cell phone records that provide
`
`a comprehensive chronicle of the user’s past movements.
`I
`
`A
`
`There are 396 million cell phone service accounts in the
`
`
`United States—for a Nation of 326 million people. Cell
`phones perform their wide and growing variety of func-
`tions by connecting to a set of radio antennas called “cell
`sites.” Although cell sites are usually mounted on a tower,
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`they can also be found on light posts, flagpoles, church
`
`steeples, or the sides of buildings. Cell sites typically have
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`several directional antennas that divide the covered area
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`into sectors.
`Cell phones continuously scan their environment look-
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`ing for the best signal, which generally comes from the
`closest cell site. Most modern devices, such as
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`smartphones, tap into the wireless network several times
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`

`2
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` CARPENTER v. UNITED STATES
`
`Opinion of the Court
`a minute whenever their signal is on, even if the owner is
`not using one of the phone’s features. Each time the
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`phone connects to a cell site, it generates a time-stamped
`record known as cell-site location information (CSLI). The
`precision of this information depends on the size of the
`geographic area covered by the cell site. The greater the
`
`concentration of cell sites, the smaller the coverage area.
`
`As data usage from cell phones has increased, wireless
`
`carriers have installed more cell sites to handle the traffic.
`That has led to increasingly compact coverage areas,
`especially in urban areas.
`
`
`Wireless carriers collect and store CSLI for their own
`business purposes, including finding weak spots in their
`network and applying “roaming” charges when another
`carrier routes data through their cell sites. In addition,
`
`wireless carriers often sell aggregated location records to
`data brokers, without individual identifying information of
`the sort at issue here. While carriers have long retained
`CSLI for the start and end of incoming calls, in recent
`years phone companies have also collected location infor-
`mation from the transmission of text messages and rou-
`tine data connections. Accordingly, modern cell phones
`generate increasingly vast amounts of increasingly precise
`CSLI.
`
`
`
`
`B
`
`In 2011, police officers arrested four men suspected of
`robbing a series of Radio Shack and (ironically enough) T-
`Mobile stores in Detroit. One of the men confessed that,
`over the previous four months, the group (along with a
`
`rotating cast of getaway drivers and lookouts) had robbed
`nine different stores in Michigan and Ohio. The suspect
`identified 15 accomplices who had participated in the
`
`heists and gave the FBI some of their cell phone numbers;
`the FBI then reviewed his call records to identify addi-
`tional numbers that he had called around the time of the
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`

`

`
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`
` Cite as: 585 U. S. ____ (2018)
`
`Opinion of the Court
`
`3
`
`
`
`robberies.
`
`Based on that information, the prosecutors applied for
`court orders under the Stored Communications Act to
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`obtain cell phone records for petitioner Timothy Carpenter
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`and several other suspects. That statute, as amended in
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`1994, permits the Government to compel the disclosure of
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`certain telecommunications records when it “offers specific
`and articulable facts showing that there are reasonable
`grounds to believe” that the records sought “are relevant
`
`and material to an ongoing criminal investigation.” 18
`
`U. S. C. §2703(d). Federal Magistrate Judges issued two
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`orders directing Carpenter’s wireless carriers—MetroPCS
`and Sprint—to disclose “cell/site sector [information] for
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`[Carpenter’s] telephone[ ] at call origination and at call
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`termination for incoming and outgoing calls” during the
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`four-month period when the string of robberies occurred.
`
`App. to Pet. for Cert. 60a, 72a. The first order sought 152
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`days of cell-site records from MetroPCS, which produced
`records spanning 127 days. The second order requested
`
`seven days of CSLI from Sprint, which produced two days
`of records covering the period when Carpenter’s phone was
`“roaming” in northeastern Ohio. Altogether the Govern-
`ment obtained 12,898 location points cataloging Carpen-
`
`ter’s movements—an average of 101 data points per day.
`
`
`Carpenter was charged with six counts of robbery and
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`an additional six counts of carrying a firearm during a
`federal crime of violence. See 18 U. S. C. §§924(c), 1951(a).
`Prior to trial, Carpenter moved to suppress the cell-site
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`data provided by the wireless carriers. He argued that the
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`Government’s seizure of the records violated the Fourth
`Amendment because they had been obtained without a
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`warrant supported by probable cause. The District Court
`denied the motion. App. to Pet. for Cert. 38a–39a.
`
`At trial, seven of Carpenter’s confederates pegged him
`as the leader of the operation. In addition, FBI agent
`Christopher Hess offered expert testimony about the cell-
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`

`

`4
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` CARPENTER v. UNITED STATES
`
`Opinion of the Court
`site data. Hess explained that each time a cell phone taps
`
`into the wireless network, the carrier logs a time-stamped
`record of the cell site and particular sector that were used.
`
`With this information, Hess produced maps that placed
`Carpenter’s phone near four of the charged robberies. In
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`the Government’s view, the location records clinched the
`case: They confirmed that Carpenter was “right where the
`. . . robbery was at the exact time of the robbery.” App.
`
`131 (closing argument). Carpenter was convicted on all
`but one of the firearm counts and sentenced to more than
`
`100 years in prison.
`The Court of Appeals for the Sixth Circuit affirmed. 819
`
`
`F. 3d 880 (2016). The court held that Carpenter lacked a
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`reasonable expectation of privacy in the location infor-
`mation collected by the FBI because he had shared that
`information with his wireless carriers. Given that cell
`phone users voluntarily convey cell-site data to their
`
`carriers as “a means of establishing communication,” the
`court concluded that the resulting business records are not
`
`entitled to Fourth Amendment protection. Id., at 888
`(quoting Smith v. Maryland, 442 U. S. 735, 741 (1979)).
`We granted certiorari. 582 U. S. ___ (2017).
`
`
`II
`
`
`A
`
`The Fourth Amendment protects “[t]he right of the
`
`
`people to be secure in their persons, houses, papers, and
`
` effects, against unreasonable searches and seizures.” The
`
`“basic purpose of this Amendment,” our cases have recog-
`nized, “is to safeguard the privacy and security of individ-
`uals against arbitrary invasions by governmental offi-
`cials.” Camara v. Municipal Court of City and County of
`
`
`San Francisco, 387 U. S. 523, 528 (1967). The Founding
`generation crafted the Fourth Amendment as a “response
`
`to the reviled ‘general warrants’ and ‘writs of assistance’ of
`the colonial era, which allowed British officers to rum-
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`

`

`5
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`
`Cite as: 585 U. S. ____ (2018)
`
`Opinion of the Court
`mage through homes in an unrestrained search for evi-
`dence of criminal activity.” Riley v. California, 573 U. S.
`
`___, ___ (2014) (slip op., at 27). In fact, as John Adams
`recalled, the patriot James Otis’s 1761 speech condemning
`writs of assistance was “the first act of opposition to the
`
`arbitrary claims of Great Britain” and helped spark the
`
`
`Revolution itself. Id., at ___–___ (slip op., at 27–28) (quot-
`ing 10 Works of John Adams 248 (C. Adams ed. 1856)).
`
`
`For much of our history, Fourth Amendment search
`doctrine was “tied to common-law trespass” and focused on
`whether the Government “obtains information by physi-
`
`cally intruding on a constitutionally protected area.”
`
`
`United States v. Jones, 565 U. S. 400, 405, 406, n. 3 (2012).
`
`More recently, the Court has recognized that “property
`
`rights are not the sole measure of Fourth Amendment
`
`
`violations.” Soldal v. Cook County, 506 U. S. 56, 64
`
`(1992). In Katz v. United States, 389 U. S. 347, 351 (1967),
`
`we established that “the Fourth Amendment protects
`people, not places,” and expanded our conception of the
`Amendment to protect certain expectations of privacy as
`well. When an individual “seeks to preserve something as
`private,” and his expectation of privacy is “one that society
`is prepared to recognize as reasonable,” we have held that
`official intrusion into that private sphere generally quali-
`fies as a search and requires a warrant supported by
`probable cause. Smith, 442 U. S., at 740 (internal quota-
`tion marks and alterations omitted).
`
`
`Although no single rubric definitively resolves which
`expectations of privacy are entitled to protection,1 the
`
`——————
`1 JUSTICE KENNEDY believes that there is such a rubric—the “proper-
`
`
`
`ty-based concepts” that Katz purported to move beyond. Post, at 3
`(dissenting opinion). But while property rights are often informative,
`
`
`our cases by no means suggest that such an interest is “fundamental”
`or “dispositive” in determining which expectations of privacy are
`legitimate. Post, at 8–9. JUSTICE THOMAS (and to a large extent
`JUSTICE GORSUCH) would have us abandon Katz and return to an
`
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`

`6
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`CARPENTER v. UNITED STATES
`
`Opinion of the Court
` analysis is informed by historical understandings “of what
`
`was deemed an unreasonable search and seizure when
`[the Fourth Amendment] was adopted.” Carroll v. United
`States, 267 U. S. 132, 149 (1925). On this score, our cases
`
`have recognized some basic guideposts. First, that the
`
`Amendment seeks to secure “the privacies of life” against
`“arbitrary power.” Boyd v. United States, 116 U. S. 616,
`
`630 (1886). Second, and relatedly, that a central aim of
`the Framers was “to place obstacles in the way of a too
`
`permeating police surveillance.” United States v. Di Re,
`
`332 U. S. 581, 595 (1948).
`We have kept this attention to Founding-era under-
`
`standings in mind when applying the Fourth Amendment
`to innovations in surveillance tools. As technology has
`enhanced the Government’s capacity to encroach upon
`areas normally guarded from inquisitive eyes, this Court
`has sought to “assure[ ] 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 (2001). For that reason, we rejected in Kyllo a
`“mechanical interpretation” of the Fourth Amendment and
`held that use of a thermal imager to detect heat radiating
`from the side of the defendant’s home was a search. Id., at
`35. Because any other conclusion would leave homeown-
`ers “at the mercy of advancing technology,” we determined
`that the Government—absent a warrant—could not capi-
`
`talize on such new sense-enhancing technology to explore
`——————
`exclusively property-based approach. Post, at 1–2, 17–21 (THOMAS J.,
`
`dissenting); post, at 6–9 (GORSUCH, J., dissenting). Katz of course
`
`“discredited” the “premise that property interests control,” 389 U. S., at
`
`353, and we have repeatedly emphasized that privacy interests do not
`
`
`rise or fall with property rights, see, e.g., United States v. Jones, 565
`
`U. S. 400, 411 (2012) (refusing to “make trespass the exclusive test”);
`Kyllo v. United States, 533 U. S. 27, 32 (2001) (“We have since decou-
`pled violation of a person’s Fourth Amendment rights from trespassory
`
`violation of his property.”). Neither party has asked the Court to
`reconsider Katz in this case.
`
`
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`

`
`
`7
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` Cite as: 585 U. S. ____ (2018)
`
`Opinion of the Court
` what was happening within the home. Ibid.
`
` Likewise in Riley, the Court recognized the “immense
`storage capacity” of modern cell phones in holding that
`
`police officers must generally obtain a warrant before
`searching the contents of a phone. 573 U. S., at ___ (slip
`op., at 17). We explained that while the general rule
`allowing warrantless searches incident to arrest “strikes
`the appropriate balance in the context of physical objects,
`neither of its rationales has much force with respect to”
`the vast store of sensitive information on a cell phone. Id.,
`at ___ (slip op., at 9).
`
`B
`The case before us involves the Government’s acquisi-
`
`tion of wireless carrier cell-site records revealing the
`
`
`location of Carpenter’s cell phone whenever it made or
`
`received calls. This sort of digital data—personal location
`
`information maintained by a third party—does not fit
`neatly under existing precedents. Instead, requests for
`cell-site records lie at the intersection of two lines of cases,
`both of which inform our understanding of the privacy
`
`interests at stake.
`The first set of cases addresses a person’s expectation of
`
`privacy in his physical location and movements. In United
`
`
`States v. Knotts, 460 U. S. 276 (1983), we considered the
`Government’s use of a “beeper” to aid in tracking a vehicle
`
`through traffic. Police officers in that case planted a
`beeper in a container of chloroform before it was pur-
`chased by one of Knotts’s co-conspirators. The officers
`(with intermittent aerial assistance) then followed the
`automobile carrying the container from Minneapolis to
`Knotts’s cabin in Wisconsin, relying on the beeper’s signal
`to help keep the vehicle in view. The Court concluded that
`
`the “augment[ed]” visual surveillance did not constitute a
`search because “[a] person traveling in an automobile on
`public thoroughfares has no reasonable expectation of
`
`
`
`

`

`8
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`
`
`
` CARPENTER v. UNITED STATES
`
`Opinion of the Court
` privacy in his movements from one place to another.” Id.,
`
`at 281, 282. Since the movements of the vehicle and its
`final destination had been “voluntarily conveyed to anyone
`who wanted to look,” Knotts could not assert a privacy
`
`interest in the information obtained. Id., at 281.
`This Court in Knotts, however, was careful to distin-
`
`guish between the rudimentary tracking facilitated by the
`
`beeper and more sweeping modes of surveillance. The
`
`Court emphasized the “limited use which the government
`made of the signals from this particular beeper” during a
`
`discrete “automotive journey.” Id., at 284, 285. Signifi-
`cantly, the Court reserved the question whether “different
`
`constitutional principles may be applicable” if “twenty-four
`
`hour surveillance of any citizen of this country [were]
`possible.” Id., at 283–284.
`
`Three decades later, the Court considered more sophis-
`ticated surveillance of the sort envisioned in Knotts and
`found that different principles did indeed apply. In United
`States v. Jones, FBI agents installed a GPS tracking de-
`vice on Jones’s vehicle and remotely monitored the vehi-
`cle’s movements for 28 days. The Court decided the case
`based on the Government’s physical trespass of the vehi-
`
`cle. 565 U. S., at 404–405. At the same time, five Justices
`
`agreed that related privacy concerns would be raised by,
`
`for example, “surreptitiously activating a stolen vehicle
`
`detection system” in Jones’s car to track Jones himself, or
`
`conducting GPS tracking of his cell phone. Id., at 426, 428
`judgment);
`id., at 415
`in
`(ALITO, J., concurring
`
`(SOTOMAYOR, J., concurring). Since GPS monitoring of a
`vehicle tracks “every movement” a person makes in that
`
`vehicle, the concurring Justices concluded that “longer
`
`term GPS monitoring in investigations of most offenses
`impinges on expectations of privacy”—regardless whether
`those movements were disclosed to the public at large.
`
`
`Id., at 430 (opinion of ALITO, J.); id., at 415 (opinion of
`
`
`
`

`

`
`
`
`Cite as: 585 U. S. ____ (2018)
`
`Opinion of the Court
`
`9
`
`
` SOTOMAYOR, J.).2
`In a second set of decisions, the Court has drawn a line
`
`
`between what a person keeps to himself and what he
`shares with others. We have previously held that “a per-
`son has no legitimate expectation of privacy in information
`he voluntarily turns over to third parties.” Smith, 442
`
`U. S., at 743–744. That remains true “even if the infor-
`mation is revealed on the assumption that it will be used
`only for a limited purpose.” United States v. Miller, 425
`
`U. S. 435, 443 (1976). As a result, the Government is
`typically free to obtain such information from the recipient
`
`without triggering Fourth Amendment protections.
`This third-party doctrine largely traces its roots to
`
`
`Miller. While investigating Miller for tax evasion, the
`Government subpoenaed his banks, seeking several
`
`months of canceled checks, deposit slips, and monthly
`
`statements. The Court rejected a Fourth Amendment
`challenge to the records collection. For one, Miller could
`“assert neither ownership nor possession” of the docu-
`ments; they were “business records of the banks.” Id., at
`440. For another, the nature of those records confirmed
`
`Miller’s limited expectation of privacy, because the checks
`
`were “not confidential communications but negotiable
`
`instruments to be used in commercial transactions,” and
`the bank statements contained information “exposed to
`——————
`
` 2 JUSTICE KENNEDY argues that this case is in a different category
`
` from Jones and the dragnet-type practices posited in Knotts because the
`
` disclosure of the cell-site records was subject to “judicial authorization.”
`
`
`
` Post, at 14–16. That line of argument conflates the threshold question
` whether a “search” has occurred with the separate matter of whether
`
`
`the search was reasonable. The subpoena process set forth in the
`
`Stored Communications Act does not determine a target’s expectation
` of privacy. And in any event, neither Jones nor Knotts purported to
`
`
`resolve the question of what authorization may be required to conduct
`
` such electronic surveillance techniques. But see Jones, 565 U. S., at
`430 (ALITO, J., concurring in judgment) (indicating that longer term
`GPS tracking may require a warrant).
`
`
`
`
`
`
`
`

`

`10
`
`
`
`
` CARPENTER v. UNITED STATES
`
`Opinion of the Court
` [bank] employees in the ordinary course of business.” Id.,
`
`at 442. The Court thus concluded that Miller had “take[n]
`the risk, in revealing his affairs to another, that the in-
`formation [would] be conveyed by that person to the Gov-
`ernment.” Id., at 443.
`Three years later, Smith applied the same principles in
`
`the context of information conveyed to a telephone com-
`pany. The Court ruled that the Government’s use of a pen
`register—a device that recorded the outgoing phone num-
`bers dialed on a landline telephone—was not a search.
`
`Noting the pen register’s “limited capabilities,” the Court
`“doubt[ed] that people in general entertain any actual
`
`expectation of privacy in the numbers they dial.” 442
`U. S., at 742. Telephone subscribers know, after all, that
`
`the numbers are used by the telephone company “for a
`variety of legitimate business purposes,” including routing
`
`calls. Id., at 743. And at any rate, the Court explained,
`such an expectation “is not one that society is prepared to
`
`recognize as reasonable.” Ibid. (internal quotation marks
`omitted). When Smith placed a call, he “voluntarily con-
`veyed” the dialed numbers to the phone company by “ex-
`pos[ing] that information to its equipment in the ordinary
`
`course of business.” Id., at 744 (internal quotation marks
`omitted). Once again, we held that the defendant “as-
`sumed the risk” that the company’s records “would be
`divulged to police.” Id., at 745.
`
`III
`
`
`The question we confront today is how to apply the
`Fourth Amendment to a new phenomenon: the ability to
`chronicle a person’s past movements through the record of
`
`his cell phone signals. Such tracking partakes of many of
`
`the qualities of the GPS monitoring we considered in
`Jones. Much like GPS tracking of a vehicle, cell phone
`location information is detailed, encyclopedic, and effort-
`
`lessly compiled.
`
`
`
`

`

`
`
`
`11
`
`
`Cite as: 585 U. S. ____ (2018)
`
`Opinion of the Court
`At the same time, the fact that the individual continu-
`
`ously reveals his location to his wireless carrier implicates
`
`the third-party principle of Smith and Miller. But while
`the third-party doctrine applies to telephone numbers and
`bank records, it is not clear whether its logic extends to
`the qualitatively different category of cell-site records.
`
`After all, when Smith was decided in 1979, few could have
`
`imagined a society in which a phone goes wherever its
`
`owner goes, conveying to the wireless carrier not just
`
`dialed digits, but a detailed and comprehensive record of
`
`the person’s movements.
`We decline to extend Smith and Miller to cover these
`
`
`novel circumstances. Given the unique nature of cell
`
`phone location records, the fact that the information is
`held by a third party does not by itself overcome the user’s
`
` claim to Fourth Amendment protection. Whether the
`
` Government employs its own surveillance technology as in
`
`Jones or leverages the technology of a wireless carrier, we
`
`hold that an individual maintains a legitimate expectation
`of privacy in the record of his physical movements as
`captured through CSLI. The location information ob-
` tained from Carpenter’s wireless carriers was the product
`
`
`of a search.3
`
`
`
`——————
`
` 3The parties suggest as an alternative to their primary submissions
`
`
` that the acquisition of CSLI becomes a search only if it extends beyond
`
`a limited period. See Reply Brief 12 (proposing a 24-hour cutoff); Brief
`for United States 55–56 (suggesting a seven-day cutoff). As part of its
`
`argument, the Government treats the seven days of CSLI requested
`from Sprint as the pertinent period, even though Sprint produced only
`
` two days of records. Brief for United States 56. Contrary to JUSTICE
`
`KENNEDY’s assertion, post, at 19, we need not decide whether there is a
`
` limited period for which the Government may obtain an individual’s
`historical CSLI free from Fourth Amendment scrutiny, and if so, how
`
`long that period might be. It is sufficient for our purposes today to hold
`
`that accessing seven days of CSLI constitutes a Fourth Amendment
`
` search.
`
`
`
`

`

`
`
` CARPENTER v. UNITED STATES
`
`Opinion of the Court
`A
`
`A person does not surrender all Fourth Amendment
`protection by venturing into the public sphere. To the
`contrary, “what [one] seeks to preserve as private, even in
`an area accessible to the public, may be constitutionally
`
`protected.” Katz, 389 U. S., at 351–352. A majority of this
`
`Court has already recognized that individuals have a
`reasonable expectation of privac