Task: sc_decisiondirection

What follows is an opinion from the Supreme Court of the United States. Your task is to determine the ideological "direction" of the decision ("liberal", "conservative", or "unspecifiable"). Use "unspecifiable" if the issue does not lend itself to a liberal or conservative description (e.g., a boundary dispute between two states, real property, wills and estates), or because no convention exists as to which is the liberal side and which is the conservative side (e.g., the legislative veto). Specification of the ideological direction comports with conventional usage. In the context of issues pertaining to criminal procedure, civil rights, First Amendment, due process, privacy, and attorneys, consider liberal to be pro-person accused or convicted of crime, or denied a jury trial, pro-civil liberties or civil rights claimant, especially those exercising less protected civil rights (e.g., homosexuality), pro-child or juvenile, pro-indigent pro-Indian, pro-affirmative action, pro-neutrality in establishment clause cases, pro-female in abortion, pro-underdog, anti-slavery, incorporation of foreign territories anti-government in the context of due process, except for takings clause cases where a pro-government, anti-owner vote is considered liberal except in criminal forfeiture cases or those where the taking is pro-business violation of due process by exercising jurisdiction over nonresident, pro-attorney or governmental official in non-liability cases, pro-accountability and/or anti-corruption in campaign spending pro-privacy vis-a-vis the 1st Amendment where the privacy invaded is that of mental incompetents, pro-disclosure in Freedom of Information Act issues except for employment and student records. In the context of issues pertaining to unions and economic activity, consider liberal to be pro-union except in union antitrust where liberal = pro-competition, pro-government, anti-business anti-employer, pro-competition, pro-injured person, pro-indigent, pro-small business vis-a-vis large business pro-state/anti-business in state tax cases, pro-debtor, pro-bankrupt, pro-Indian, pro-environmental protection, pro-economic underdog pro-consumer, pro-accountability in governmental corruption, pro-original grantee, purchaser, or occupant in state and territorial land claims anti-union member or employee vis-a-vis union, anti-union in union antitrust, anti-union in union or closed shop, pro-trial in arbitration. In the context of issues pertaining to judicial power, consider liberal to be pro-exercise of judicial power, pro-judicial "activism", pro-judicial review of administrative action. In the context of issues pertaining to federalism, consider liberal to be pro-federal power, pro-executive power in executive/congressional disputes, anti-state. In the context of issues pertaining to federal taxation, consider liberal to be pro-United States and conservative pro-taxpayer. In miscellaneous, consider conservative the incorporation of foreign territories and executive authority vis-a-vis congress or the states or judcial authority vis-a-vis state or federal legislative authority, and consider liberal legislative veto. In interstate relations and private law issues, consider unspecifiable in all cases.

Chief Justice ROBERTS delivered the opinion of the Court.
This case presents the question whether the Government 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 functions by connecting to a set of radio antennas called "cell sites." Although cell sites are usually mounted on a tower, they can also be found on light posts, flagpoles, church steeples, or the sides of buildings. Cell sites typically have several directional antennas that divide the covered area into sectors.
Cell phones continuously scan their environment looking for the best signal, which generally comes from the closest cell site. Most modern devices, such as smartphones, tap into the wireless network several times a minute whenever their signal is on, even if the owner is not using one of the phone's features. Each time the 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 information from the transmission of text messages and routine 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 additional numbers that he had called around the time of the robberies.
Based on that information, the prosecutors applied for court orders under the Stored Communications Act to obtain cell phone records for petitioner Timothy Carpenter and several other suspects. That statute, as amended in 1994, permits the Government to compel the disclosure of 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 orders directing Carpenter's wireless carriers-MetroPCS and Sprint-to disclose "cell/site sector [information] for [Carpenter's] telephone[ ] at call origination and at call termination for incoming and outgoing calls" during the four-month period when the string of robberies occurred. App. to Pet. for Cert. 60a, 72a. The first order sought 152 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 Government obtained 12,898 location points cataloging Carpenter's movements-an average of 101 data points per day.
Carpenter was charged with six counts of robbery and 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 data provided by the wireless carriers. He argued that the Government's seizure of the records violated the Fourth Amendment because they had been obtained without a 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-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 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 reasonable expectation of privacy in the location information 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, 99 S.Ct. 2577, 61 L.Ed.2d 220 (1979) ).
We granted certiorari. 582 U.S. ----, 137 S.Ct. 2211, 198 L.Ed.2d 657 (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 recognized, "is to safeguard the privacy and security of individuals against arbitrary invasions by governmental officials." Camara v. Municipal Court of City and County of San Francisco, 387 U.S. 523, 528, 87 S.Ct. 1727, 18 L.Ed.2d 930 (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 rummage through homes in an unrestrained search for evidence of criminal activity." Riley v. California, 573 U.S. ----, ----, 134 S.Ct. 2473, 2494, 189 L.Ed.2d 430 (2014). 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 ---- - ----, 134 S.Ct., at 2494 (quoting 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 physically intruding on a constitutionally protected area." United States v. Jones, 565 U.S. 400, 405, 406, n. 3, 132 S.Ct. 945, 181 L.Ed.2d 911 (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, 113 S.Ct. 538, 121 L.Ed.2d 450 (1992). In Katz v. United States, 389 U.S. 347, 351, 88 S.Ct. 507, 19 L.Ed.2d 576 (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 qualifies as a search and requires a warrant supported by probable cause. Smith, 442 U.S., at 740, 99 S.Ct. 2577 (internal quotation marks and alterations omitted).
Although no single rubric definitively resolves which expectations of privacy are entitled to protection, the 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, 45 S.Ct. 280, 69 L.Ed. 543 (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, 6 S.Ct. 524, 29 L.Ed. 746 (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, 68 S.Ct. 222, 92 L.Ed. 210 (1948).
We have kept this attention to Founding-era understandings 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, 121 S.Ct. 2038, 150 L.Ed.2d 94 (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, 121 S.Ct. 2038. Because any other conclusion would leave homeowners "at the mercy of advancing technology," we determined that the Government-absent a warrant-could not capitalize on such new sense-enhancing technology to explore 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 ----, 134 S.Ct., at 2489. 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 ----, 134 S.Ct., at 2484.
B
The case before us involves the Government's acquisition 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, 103 S.Ct. 1081, 75 L.Ed.2d 55 (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 purchased 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 privacy in his movements from one place to another." Id., at 281, 282, 103 S.Ct. 1081. 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, 103 S.Ct. 1081.
This Court in Knotts, however, was careful to distinguish 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, 103 S.Ct. 1081. Significantly, 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, 103 S.Ct. 1081.
Three decades later, the Court considered more sophisticated 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 device on Jones's vehicle and remotely monitored the vehicle's movements for 28 days. The Court decided the case based on the Government's physical trespass of the vehicle. 565 U.S., at 404-405, 132 S.Ct. 945. 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, 132 S.Ct. 945 (ALITO, J., concurring in judgment); id., at 415, 132 S.Ct. 945 (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, 132 S.Ct. 945 (opinion of Alito, J.); id., at 415, 132 S.Ct. 945 (opinion of Sotomayor, J.).
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 person has no legitimate expectation of privacy in information he voluntarily turns over to third parties." Smith, 442 U.S., at 743-744, 99 S.Ct. 2577. That remains true "even if the information is revealed on the assumption that it will be used only for a limited purpose." United States v. Miller, 425 U.S. 435, 443, 96 S.Ct. 1619, 48 L.Ed.2d 71 (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 documents; they were "business records of the banks." Id., at 440, 96 S.Ct. 1619. 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 [bank] employees in the ordinary course of business." Id., at 442, 96 S.Ct. 1619. The Court thus concluded that Miller had "take[n] the risk, in revealing his affairs to another, that the information [would] be conveyed by that person to the Government." Id., at 443, 96 S.Ct. 1619.
Three years later, Smith applied the same principles in the context of information conveyed to a telephone company. The Court ruled that the Government's use of a pen register-a device that recorded the outgoing phone numbers 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, 99 S.Ct. 2577. 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, 99 S.Ct. 2577. 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 conveyed" the dialed numbers to the phone company by "expos[ing] that information to its equipment in the ordinary course of business." Id., at 744, 99 S.Ct. 2577 (internal quotation marks omitted). Once again, we held that the defendant "assumed the risk" that the company's records "would be divulged to police." Id., at 745, 99 S.Ct. 2577.
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 effortlessly compiled.
At the same time, the fact that the individual continuously 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 obtained from Carpenter's wireless carriers was the product of a search.
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, 88 S.Ct. 507. A majority of this Court has already recognized that individuals have a reasonable expectation of privacy in the whole of their physical movements. Jones, 565 U.S., at 430, 132 S.Ct. 945 (ALITO, J., concurring in judgment); id., at 415, 132 S.Ct. 945 (SOTOMAYOR, J., concurring). Prior to the digital age, law enforcement might have pursued a suspect for a brief stretch, but doing so "for any extended period of time was difficult and costly and therefore rarely undertaken." Id., at 429, 132 S.Ct. 945 (opinion of Alito, J.). For that reason, "society's expectation has been that law enforcement agents and others would not-and indeed, in the main, simply could not-secretly monitor and catalogue every single movement of an individual's car for a very long period." Id., at 430, 132 S.Ct. 945.
Allowing government access to cell-site records contravenes that expectation. Although such records are generated for commercial purposes, that distinction does not negate Carpenter's anticipation of privacy in his physical location. Mapping a cell phone's location over the course of 127 days provides an all-encompassing record of the holder's whereabouts. As with GPS information, the time-stamped data provides an intimate window into a person's life, revealing not only his particular movements, but through them his "familial, political, professional, religious, and sexual associations." Id., at 415, 132 S.Ct. 945 (opinion of SOTOMAYOR, J.). These location records "hold for many Americans the 'privacies of life.' " Riley, 573 U.S., at ----, 134 S.Ct., at 2494-2495 (quoting Boyd, 116 U.S., at 630, 6 S.Ct. 524 ). And like GPS monitoring, cell phone tracking is remarkably easy, cheap, and efficient compared to traditional investigative tools. With just the click of a button, the Government can access each carrier's deep repository of historical location information at practically no expense.
In fact, historical cell-site records present even greater privacy concerns than the GPS monitoring of a vehicle we considered in Jones. Unlike the bugged container in Knotts or the car in Jones, a cell phone-almost a "feature of human anatomy," Riley, 573 U.S., at ----, 134 S.Ct., at 2484 -tracks nearly exactly the movements of its owner. While individuals regularly leave their vehicles, they compulsively carry cell phones with them all the time. A cell phone faithfully follows its owner beyond public thoroughfares and into private residences, doctor's offices, political headquarters, and other potentially revealing locales. See id., at ----, 134 S.Ct., at 2490 (noting that "nearly three-quarters of smart phone users report being within five feet of their phones most of the time, with 12% admitting that they even use their phones in the shower"); contrast Cardwell v. Lewis, 417 U.S. 583, 590, 94 S.Ct. 2464, 41 L.Ed.2d 325 (1974) (plurality opinion) ("A car has little capacity for escaping public scrutiny."). Accordingly, when the Government tracks the location of a cell phone it achieves near perfect surveillance, as if it had attached an ankle monitor to the phone's user.
Moreover, the retrospective quality of the data here gives police access to a category of information otherwise unknowable. In the past, attempts to reconstruct a person's movements were limited by a dearth of records and the frailties of recollection. With access to CSLI, the Government can now travel back in time to retrace a person's whereabouts, subject only to the retention polices of the wireless carriers, which currently maintain records for up to five years. Critically, because location information is continually logged for all of the 400 million devices in the United States-not just those belonging to persons who might happen to come under investigation-this newfound tracking capacity runs against everyone. Unlike with the GPS device in Jones, police need not even know in advance whether they want to follow a particular individual, or when.
Whoever the suspect turns out to be, he has effectively been tailed every moment of every day for five years, and the police may-in the Government's view-call upon the results of that surveillance without regard to the constraints of the Fourth Amendment. Only the few without cell phones could escape this tireless and absolute surveillance.
The Government and Justice KENNEDY contend, however, that the collection of CSLI should be permitted because the data is less precise than GPS information. Not to worry, they maintain, because the location records did "not on their own suffice to place [Carpenter] at the crime scene"; they placed him within a wedge-shaped sector ranging from one-eighth to four square miles. Brief for United States 24; see post, at 2232 - 2233. Yet the Court has already rejected the proposition that "inference insulates a search." Kyllo, 533 U.S., at 36, 121 S.Ct. 2038. From the 127 days of location data it received, the Government could, in combination with other information, deduce a detailed log of Carpenter's movements, including when he was at the site of the robberies. And the Government thought the CSLI accurate enough to highlight it during the closing argument of his trial. App. 131.
At any rate, the rule the Court adopts "must take account of more sophisticated systems that are already in use or in development."
Kyllo, 533 U.S., at 36, 121 S.Ct. 2038. While the records in this case reflect the state of technology at the start of the decade, the accuracy of CSLI is rapidly approaching GPS-level precision. As the number of cell sites has proliferated, the geographic area covered by each cell sector has shrunk, particularly in urban areas. In addition, with new technology measuring the time and angle of signals hitting their towers, wireless carriers already have the capability to pinpoint a phone's location within 50 meters. Brief for Electronic Frontier Foundation et al. as Amici Curiae 12 (describing triangulation methods that estimate a device's location inside a given cell sector).
Accordingly, when the Government accessed CSLI from the wireless carriers, it invaded Carpenter's reasonable expectation of privacy in the whole of his physical movements.
B
The Government's primary contention to the contrary is that the third-party doctrine governs this case. In its view, cell-site records are fair game because they are "business records" created and maintained by the wireless carriers. The Government (along with Justice KENNEDY) recognizes that this case features new technology, but asserts that the legal question nonetheless turns on a garden-variety request for information from a third-party witness. Brief for United States 32-34; post, at 2229 - 2231.
The Government's position fails to contend with the seismic shifts in digital technology that made possible the tracking of not only Carpenter's location but also everyone else's, not for a short period but for years and years. Sprint Corporation and its competitors are not your typical witnesses. Unlike the nosy neighbor who keeps an eye on comings and goings, they are ever alert, and their memory is nearly infallible. There is a world of difference between the limited types of personal information addressed in Smith and Miller and the exhaustive chronicle of location information casually collected by wireless carriers today. The Government thus is not asking for a straightforward application of the third-party doctrine, but instead a significant extension of it to a distinct category of information.
The third-party doctrine partly stems from the notion that an individual has a reduced expectation of privacy in information knowingly shared with another. But the fact of "diminished privacy interests does not mean that the Fourth Amendment falls out of the picture entirely." Riley, 573 U.S., at ----, 134 S.Ct., at 2488. Smith and Miller, after all, did not rely solely on the act of sharing. Instead, they considered "the nature of the particular documents sought" to determine whether "there is a legitimate 'expectation of privacy' concerning their contents." Miller, 425 U.S., at 442, 96 S.Ct. 1619. Smith pointed out the limited capabilities of a pen register; as explained in Riley, telephone call logs reveal little in the way of "identifying information." Smith, 442 U.S., at 742, 99 S.Ct. 2577 ; Riley, 573 U.S., at ----, 134 S.Ct., at 2493. Miller likewise noted that checks were "not confidential communications but negotiable instruments to be used in commercial transactions." 425 U.S., at 442, 96 S.Ct. 1619. In mechanically applying the third-party doctrine to this case, the Government fails to appreciate that there are no comparable limitations on the revealing nature of CSLI.
The Court has in fact already shown special solicitude for location information in the third-party context. In Knotts, the Court relied on Smith to hold that an individual has no reasonable expectation of privacy in public movements that he "voluntarily conveyed to anyone who wanted to look." Knotts, 460 U.S., at 281, 103 S.Ct. 1081 ; see id., at 283, 103 S.Ct. 1081 (discussing Smith ). But when confronted with more pervasive tracking, five Justices agreed that longer term GPS monitoring of even a vehicle traveling on public streets constitutes a search. Jones, 565 U.S., at 430, 132 S.Ct. 945 (ALITO, J., concurring in judgment); id., at 415, 132 S.Ct. 945 (SOTOMAYOR, J., concurring). Justice GORSUCH wonders why "someone's location when using a phone" is sensitive, post, at 2262, and Justice KENNEDY assumes that a person's discrete movements "are not particularly private," post, at 2232. Yet this case is not about "using a phone" or a person's movement at a particular time. It is about a detailed chronicle of a person's physical presence compiled every day, every moment, over several years. Such a chronicle implicates privacy concerns far beyond those considered in Smith and Miller.
Neither does the second rationale underlying the third-party doctrine-voluntary exposure-hold up when it comes to CSLI. Cell phone location information is not truly "shared" as one normally understands the term. In the first place, cell phones and the services they provide are "such a pervasive and insistent part of daily life" that carrying one is indispensable to participation in modern society. Riley, 573 U.S., at ----, 134 S.Ct., at 2484. Second, a cell phone logs a cell-site record by dint of its operation, without any affirmative act on the part of the user beyond powering up. Virtually any activity on the phone generates CSLI, including incoming calls, texts, or e-mails and countless other data connections that a phone automatically makes when checking for news, weather, or social media updates. Apart from disconnecting the phone from the network, there is no way to avoid leaving behind a trail of location data. As a result, in no meaningful sense does the user voluntarily "assume[ ] the risk" of turning over a comprehensive dossier of his physical movements. Smith, 442 U.S., at 745, 99 S.Ct. 2577.
We therefore decline to extend Smith and Miller to the collection of CSLI. Given the unique nature of cell phone location information, the fact that the Government obtained the information from a third party does not overcome Carpenter's claim to Fourth Amendment protection. The Government's acquisition of the cell-site records was a search within the meaning of the Fourth Amendment.
* * *
Our decision today is a narrow one. We do not express a view on matters not before us: real-time CSLI or "tower dumps" (a download of information on all the devices that connected to a particular cell site during a particular interval). We do not disturb the application of Smith and Miller or call into question conventional surveillance techniques and tools, such as security cameras. Nor do we address other business records that might incidentally reveal location information. Further, our opinion does not consider other collection techniques involving foreign affairs or national security. As Justice Frankfurter noted when considering new innovations in airplanes and radios, the Court must tread carefully in such cases, to ensure that we do not "embarrass the future." Northwest Airlines, Inc. v. Minnesota, 322 U.S. 292, 300, 64 S.Ct. 950, 88 L.Ed. 1283 (1944).
IV
Having found that the acquisition of Carpenter's CSLI was a search, we also conclude that the Government must generally obtain a warrant supported by probable cause before acquiring such records. Although the "ultimate measure of the constitutionality of a governmental search is'reasonableness,' " our cases establish that warrantless searches are typically unreasonable where "a search is undertaken by law enforcement officials to discover evidence of criminal wrongdoing." Vernonia School Dist. 47J v. Acton, 515 U.S. 646, 652-653, 115 S.Ct. 2386, 132 L.Ed.2d 564 (1995). Thus, "[i]n the absence of a warrant, a search is reasonable only if it falls within a specific exception to the warrant requirement." Riley, 573 U.S., at ----, 134 S.Ct., at 2482.
The Government acquired the cell-site records pursuant to a court order issued under the Stored Communications 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. The Court usually requires "some quantum of individualized suspicion" before a search or seizure may take place. United States v. Martinez-Fuerte, 428 U.S. 543, 560-561, 96 S.Ct. 3074, 49 L.Ed.2d 1116 (1976). Under the standard in the Stored Communications Act, however, law enforcement need only show that the cell-site evidence might be pertinent to an ongoing investigation-a "gigantic" departure from the probable cause rule, as the Government explained below. App. 34. Consequently, an order issued under Section 2703(d) of the Act is not a permissible mechanism for accessing historical cell-site records. Before compelling a wireless carrier to turn over a subscriber's CSLI, the Government's obligation is a familiar one-get a warrant.
Justice ALITO contends that the warrant requirement simply does not apply when the Government acquires records using compulsory process. Unlike an actual search, he says, subpoenas for documents do not involve the direct taking of evidence; they are at most a "constructive search" conducted by the target of the subpoena. Post, at 2252 - 2253. Given this lesser intrusion on personal privacy, Justice ALITO argues that the compulsory production of records is not held to the same probable cause standard. In his view, this Court's precedents set forth a categorical rule-separate and distinct from the third-party doctrine-subjecting subpoenas to lenient scrutiny without regard to the suspect's expectation of privacy in the records. Post, at 2250 - 2257.
But this Court has never held that the Government may subpoena third parties for records in which the suspect has a reasonable expectation of privacy. Almost all of the examples Justice ALITO cites, see post, at 2253 - 2255, contemplated requests for evidence implicating diminished privacy interests or for a corporation's own books. The lone exception, of course, is Miller, where the Court's analysis of the third-party subpoena merged with

Question: What is the ideological direction of the decision?
A. Conservative
B. Liberal
C. Unspeciﬁable
Answer:

Answer: B