Supreme Court Rules That Cell Phone Site Data Is Protected By The Fourth Amendment

In a case that pit the new rules of cyberspace against the old rules about when the Fourth Amendment protects privacy, the Supreme Court ruled today in a way that breathes new life into both privacy and the Fourth Amendment.

Striking a significant victory for privacy rights and the Fourth Amendment in the digital world, the Supreme Court ruled today that law enforcement must obtain a search warrant based on probable cause to obtain site location data for a cell phone in most ordinary cases:

WASHINGTON — In a major statement on privacy in the digital age, the Supreme Court ruled on Friday that the government generally needs a warrant to collect troves of location data about the customers of cellphone companies.

“We decline to grant the state unrestricted access to a wireless carrier’s database of physical location information,” Chief Justice John G. Roberts Jr. wrote for the majority.

The 5-to-4 decision has implications for all kinds of personal information held by third parties, including email and text messages, internet searches, and bank and credit card records. But Chief Justice John G. Roberts Jr., writing for the majority, said the ruling was limited.

“We hold only that a warrant is required in the rare case where the suspect has a legitimate privacy interest in records held by a third party,” the chief justice wrote. The court’s four more liberal members — Justices Ruth Bader Ginsburg, Stephen G. Breyer, Sonia Sotomayor and Elena Kagan — joined his opinion.

Each of the four other justices wrote a dissent, with the five opinions running to more than 120 pages. In one dissent, Justice Anthony M. Kennedy said the distinctions drawn by the majority were illogical and “will frustrate principled application of the Fourth Amendment in many routine yet vital law enforcement operations.”

“Cell-site records,” he wrote, “are uniquely suited to help the government develop probable cause to apprehend some of the nation’s most dangerous criminals: serial killers, rapists, arsonists, robbers, and so forth.”

In a second dissent, Justice Samuel A. Alito Jr. wrote that the decision “guarantees a blizzard of litigation while threatening many legitimate and valuable investigative practices upon which law enforcement has rightfully come to rely.”


Mr. Carpenter’s lawyers said cellphone companies had turned over 127 days of records that placed his phone at 12,898 locations, based on information from cellphone towers. The records disclosed whether he had slept at home on given nights and whether he attended his usual church on Sunday mornings.

Chief Justice Roberts wrote that the information was entitled to privacy protection.

“Mapping a cell phone’s location over the course of 127 days provides an all-encompassing record of the holder’s whereabouts,” he wrote, going on to quote from an earlier opinion. “As with GPS information, the timestamped 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.'”

In dissent, Justice Kennedy wrote that GPS devices provide much more precise location information than do cell towers. Chief Justice Roberts responded that cell tower technology is developing quickly.

“As the number of cell sites has proliferated,” he wrote, “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.”

Amy Howe analyzes the opinion for SCOTUSBlog:

The issue came to the Supreme Court in the case of Timothy Carpenter, who was convicted and sentenced to almost 116 years in prison for his role in a series of armed robberies in Ohio and Michigan. Law-enforcement officials used cell-site records from his cellphone provider to place him in the vicinity of the crimes, but Carpenter argued that the jury should not hear about those records because the government had not obtained a warrant for them. A federal appeals court upheld his conviction, explaining that the government was not required to seek a warrant because Carpenter could not have expected cellphone records maintained by his service provider to remain private. This morning the Supreme Court reversed that ruling.

In a decision joined by Justices Ruth Bader Ginsburg, Stephen Breyer, Sonia Sotomayor and Elena Kagan, Roberts observed that the information collected by wireless providers is “detailed, encyclopedic, and effortlessly compiled.” He declined to extend the third-party doctrine to cover the “unique nature” of this information: When the Supreme Court decided the cases outlining the doctrine, he explained, no one could have envisioned that cellphones would be so ubiquitous and provide so much information about their users, for so many years. And, he added, because cellphones are such a pervasive part of life “that carrying one is indispensable to participation in modern society,” it can’t really be said that a cellphone user is voluntarily sharing information about his location with his carrier. Therefore, Roberts concluded, the acquisition of the cell-site location records was a search within the meaning of the Fourth Amendment, for which the government would generally have to obtain a warrant.

This isn’t the first case that the Court has encountered related to the relationship between technology, privacy rights, and the Fourth Amendment, and it’s unlikely to be the last. In 2012, for example, the Court ruled in United States v. Jones, the Court held that attaching a GPS device to a suspect’s vehicle in order to track their movements constituted a search for Fourth Amendment purposes, meaning that law enforcement would need to obtain a warrant based on probable cause before taking this step. As I noted in June of last year when the Court accepted the Carpenter case for review, Justice Sotomayor noted in a concurring opinion in the Jones case the extent to which expectations of privacy in the digital age have changed significantly from the time when the Supreme Court first held that data that was in the hands of a third party was not subject to the Fourth Amendment because users/customers did not have a reasonable expectation of privacy.

The third-party exception to the Fourth Amendment can be traced, of course, to a pair of Supreme Court cases that stretch back more than forty years. First, in a 1976 case styled United States v. Miller, the Court had ruled that bank records in the possession of a financial institution were not covered by the Fourth Amendment, holding that the records were not the records were not the private papers of the defendant, but instead the business records of the bank, and therefore not entitled to Fourth Amendment protection and not requiring a search warrant. Three years later in 1979, the Court ruled in Smith v. Maryland. that law enforcement did not need to obtain a warrant to obtain information from a phone company regarding which phone numbers had been called from or to a certain phone number because there was no reasonable expectation of privacy in that information. At that time, that was probably the case given the fact that most people were aware of the fact that their phone carrier was the one who possessed the data about who they called since that information was displayed every month on their phone bill. Taken together, these cases established the third-party exception to the Fourth Amendment, which provides that law enforcement need not obtain a search warrant to obtain data held regarding an individual in the ordinary course of business by a third-party.

As Justice Sotomayer noted in her concurrence in the Jones case, though, that expectation of privacy has arguably changed significantly in an era where the devices that we still call “phones” are used for so many other purposes and are also broadcasting all kinds of personal information without our knowledge and beyond our control. For most modern phones, that includes location data that, depending on whether or not a phones GPS location services are turned on or not, can tell anyone where our phone is. In fact, that feature has become so ubiquitous that it’s now possible to locate your phone over the Internet and even control it in various manners, such as by making it ring even if it’s on silent mode. Given this, the idea that Americans were surrendering their right to privacy regarding their location just by carrying around an electronic device doesn’t make sense. At the very least, though, it can obviously be said that the Court that decided Smith and Miller didn’t anticipate the world we live in today and that the third-party exemption they created would need to be reexamined in light of the world we live in today.

Two years after Jones, the Court ruled in Riley v. California that law enforcement could not search the contents of a cell phone or smartphone without first obtaining a warrant. This was effectively the first case in which the Court had the chance to rule upon the applicability of the Fourth Amendment in the digital age, and the decision offered some glimmer of hope that the Justices were recognizing that the rule established in the Smith case was no longer appropriate, at least not as far as the application of the questions regarding search issues to the new world of personal devices is concerned. As I noted at the time that decision came down, the Court’s ruling in Riley was a hopeful sign that the Justices recognized that Smith and Miller were no longer a sufficient guide and that the questions regarding the reasonable expectation of privacy would have to be reexamined in this new digital world. It would take future cases, though, to determine just how far the Court was willing to go in curtailing the third-party doctrine in the digital age. Today, at least in part, we got an answer.

In his opinion today, Justice Roberts relies on both of those previous cases to reach the conclusion that he did:

[T]he 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 person does not surrender all Fourth Amendmentprotection 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 privacy in the whole of their physical movements. Jones, 565 U. S., at 430 (ALITO, J., concurring in judgment); id., at 415 (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 (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.

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 timestamped 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 (opinion of SOTOMAYOR, J.). These location records  “hold for many Americans the ‘privacies of life.'” Riley, 573 U. S., at ___ (slip op., at 28) (quoting Boyd, 116 U. S., at 630). 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.


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.

One of the more notable things about today’s opinion, of course, is that Chief Justice Roberts took on the role that Justice Kennedy usually takes as the person who struck the balance in an otherwise ideologically divided today. In this case, though, Roberts ended siding with the Court’s four liberal-leaning Justices while his fellow conservatives were all in dissent, including the Court’s newest appointee Justice Neil Gorsuch. As Damon Root notes at Reason, though, Gorsuch’s dissent at times reads more like a concurrence and suggests that he thinks that he believes the Court needs to reexamine the viability of Smith and Miller not just in cases dealing with cell phone data, but in all cases:

Justice Neil Gorsuch struck an entirely different note in his lone dissent. Indeed, his dissent reads much more like a concurrence. It seems clear that while Gorsuch agreed with the majority that Carpenter deserved to win, he strongly disagreed with them about how the win should have happened.

“I would look to a more traditional Fourth Amendment approach,” Gorsuch wrote. “The Fourth Amendment protects ‘the right of the people to be secure in their persons, houses, papers and effects, against unreasonable searches and seizures.’ True to those words and their original understanding, the traditional approach asked if a house, paper or effect was yours under law. No more was needed to trigger the Fourth Amendment.” Furthermore, Gorsuch wrote, “it seems to me entirely possible a person’s cell-site data could qualify as his papers or effects under existing law.”

“I cannot fault” the majority “for its implicit but unmistakable conclusion that the rationale of Smith and Miller is wrong; indeed, I agree with that,” Gorsuch explained. “At the same time, I do not agree with the Court’s decision today to keep Smith and Miller on life support.” In other words, Gorsuch would scrap these third-party precedents and have the Court start adhering to an originalist, property rights-based theory of the Fourth Amendment. That’s how Gorsuch wanted Carpenter to win.

What this means going forward is something we’ll have to wait for future cases to find out, but Gorsuch’s suggestion could have interesting implications going forward were the Court choose to adopt it. In any case, after reading through his dissent it seems as though Justice Gorsuch ought to be counted as “concurring” in the result but not in the reasoning used by the majority to reach that result. That makes it worthwhile to keep an eye on where he falls in future Fourth Amendment cases.

It’s important to note that the Court’s decision doesn’t say that police must always get a search warrant to obtain real-time location data. In fact, Chief Justice Roberts makes clear in the opinion that the Court’s previous precedents regarding an “exigent circumstances” exception to the Fourth Amendment rule would still be available to law enforcement, for example. He also states that the Court’s ruling was limited to facts in the Carpenter case itself, which involved law enforcement accessing location data over an extended period of time to build a case against the defendant. With respect to the “exigent circumstances” exception, perhaps the best example of that would be an emergency situation such as a kidnapping where locating the suspect was necessary to potentially save the life of a victim. In those situations, the Court has ruled in the past that law enforcement does not necessarily need to go to a Judge to get a warrant to obtain data that could lead to a location where a victim was being held, or where a potential bomber might be. As the Ninth Circuit Court of Appeals put it in United States v. McConney 728 F.2d. 1195 (1984), exigent circumstances are those ”circumstances that would cause a reasonable person to believe that entry (or other relevant prompt action) was necessary to prevent physical harm to the officers or other persons, the destruction of relevant evidence, the escape of the suspect, or some other consequence improperly frustrating legitimate law enforcement efforts.” Outside of those circumstances, though, and especially in cases like Carpenter where law enforcement wants to use site location data to track a suspect over an extended period of time, today’s ruling means that police will be required to first convince a Judge that they have probable cause to believe that the information they are seeking will be, or will lead to the discovery of, admissible evidence. For that reason alone, this case is yet another hopeful sign that privacy is not dead and that the Fourth Amendment still matters.

Here’s the opinion:

Carpenter v. U.S. by Doug Mataconis on Scribd

FILED UNDER: Fourth Amendment, Law and the Courts, Supreme Court, U.S. Constitution, , , , ,
Doug Mataconis
About Doug Mataconis
Doug holds a B.A. in Political Science from Rutgers University and J.D. from George Mason University School of Law. He joined the staff of OTB in May 2010. Before joining OTB, he wrote at Below The BeltwayThe Liberty Papers, and United Liberty Follow Doug on Twitter | Facebook


  1. teve tory says:

    ACLU response:

    JUNE 22, 2018
    WASHINGTON — The Supreme Court ruled today that the government needs a warrant to access a person’s cellphone location history.

    In the case, Carpenter v. United States, the American Civil Liberties Union represents a man who had months of his cellphone location information turned over to law enforcement without a warrant.

    The court found in a 5 to 4 decision that obtaining such information is a search under the Fourth Amendment and that a warrant from a judge based on probable cause is required.

    “This is a groundbreaking victory for Americans’ privacy rights in the digital age,” said ACLU attorney Nathan Freed Wessler, who argued the case before the court last November. “The Supreme Court has given privacy law an update that it has badly needed for many years, finally bringing it in line with the realities of modern life. The government can no longer claim that the mere act of using technology eliminates the Fourth Amendment’s protections. Today’s decision rightly recognizes the need to protect the highly sensitive location data from our cell phones, but it also provides a path forward for safeguarding other sensitive digital information in future cases — from our emails, smart home appliances, and technology that is yet to be invented.”

    In 2011, without getting a probable cause warrant, the government obtained from cell service companies months’ worth of phone location records for suspects in a robbery investigation in Detroit. For one suspect, Timothy Carpenter, the records covered 127 days and revealed 12,898 separate points of location data. Police seek these kinds of cellphone location records from phone companies tens of thousands of times each year.

    After Carpenter was convicted at trial, based in part on the cellphone location evidence, he appealed to the Sixth Circuit Court of Appeals, which ruled 2–1 that no warrant is required under the Fourth Amendment.

    The Supreme Court said in its opinion today, “We decline to grant the state unrestricted access to a wireless carrier’s database of physical location information. In light of the deeply revealing nature of CSLI, its depth, breadth, and comprehensive reach, and the inescapable and automatic nature of its collection, the fact that such information is gathered by a third party does not make it any less deserving of Fourth Amendment protection. The Government’s acquisition of the cell-site records here was a search under that Amendment.”

    Among the many friend-of-the-court briefs filed in the case is the one from technology companies, which was signed by Google, Facebook, Apple, Verizon, Twitter, Cisco, Microsoft, and others. They echoed the ACLU’s arguments, writing that “Fourth Amendment doctrine must adapt to the changing realities of the digital era” and that “Rigid analog-era rules should yield to consideration of reasonable expectations of privacy in the digital age.”

    In another friend-of-the-court brief, the Reporters Committee for Freedom of the Press and 19 other media organizations warned of the chilling effect on First Amendment freedoms that can result from easy law enforcement access to the location information of reporters and their sources.

    The government’s argument was based on the “third-party doctrine,” which the government reads to provide that by sharing information or records with a “third party” such as a business, a person gives up any reasonable expectation that the information will remain private. The doctrine was established in Supreme Court cases from the 1970s, which reasoned that without an expectation of privacy, there is no Fourth Amendment protection for certain records voluntarily shared with businesses, such as canceled checks sent to a bank or phone numbers dialed on a phone and transmitted over a phone company’s equipment. The government has extended that principle to cover various kinds of digital records, such as cell phone location data.

    “The court’s decision is a vindication of the arguments we have persistently made on behalf of Timothy Carpenter throughout this litigation — that the Constitution’s privacy protections fully apply to the digital location data created by using cell phones,” said attorney Harold Gurewitz, who represents Carpenter alongside the ACLU. “The ruling also affirms that prosecutors are required to get a search warrant in order to seize this kind of sensitive personal information.”

    The data acquired by police in the case provides a stark demonstration of how location data can reveal extraordinarily private details about people’s lives, from where they sleep to where they pray.

    For example, the location data showed that in the early afternoon on a number of Sundays, Carpenter made or received calls from the cell tower sectors nearest to his church. His cellphone records do not routinely show him in that area on other days of the week, implying that he was worshipping at those times. The data also shows which nights he slept at or near his home, and which nights he spent elsewhere.

    Carpenter is represented at the Supreme Court by the ACLU, the ACLU of Michigan, defense attorney Gurewitz of Gurewitz & Raben PLC, and Jeffrey Fisher, co-director of the Stanford Law School Supreme Court Litigation Clinic.

    Today’s ruling is here:

  2. James Joyner says:

    Why didn’t Gorsuch simply write a Concurrence, rather than a dissent, if he agreed with the outcome?

    (I have to admit to being pleasantly surprised by the ruling. Like Gorsuch, I thought this was pretty much settled law in the other direction.)

  3. Michael Reynolds says:

    Well done SCOTUS, and as usual, excellent clarification and analysis @Doug.

  4. TM01 says:

    I too don’t understand why he didn’t write a Concurrence given the content of his opinion. Maybe someone with more detailed legal knowledge then I can explain? Does it affect Precedent or anything like that, or what reasoning lower courts can use for similar cases?

    Maybe we need more Gorsuchs tho. See? We don’t need a “Living Constitution.”

    Good pick by Trump there.

  5. Mister Bluster says:

    Good pick by Trump there.

    Ha! The only good trump ever picked was his nose!

  6. mattbernius says:

    @James Joyner:

    Why didn’t Gorsuch simply write a Concurrence, rather than a dissent, if he agreed with the outcome?

    With these decisions, the route one takes is as important as the outcome in that said route can be used as precedent for future arguments and decisions. In this case Gorsuch believes that Smith and Miller should be fully scrapped. So, in his opinion, signing onto this decision would be saying that there is still a place for those decisions. That’s antithetical to his judicial reasoning.

  7. Electroman says:

    @TM01: But since we are in a common-law jurisdiction, we do in fact have a “living constitution”.

  8. Stormy Dragon says:

    @James Joyner:

    Why didn’t Gorsuch simply write a Concurrence, rather than a dissent, if he agreed with the outcome?

    Maybe he doesn’t know he’s allowed to write a separate concurrence?

  9. HarvardLaw92 says:

    I haven’t read the opinion yet, but on face it looks like they took great pains to avoid overruling Smith v. Maryland, et al. The third party doctrine remains viable law. That limits the impact of this ruling somewhat.

    In other words “I need a warrant to find out where you’ve physically been located, but I can still find out what numbers you’ve dialed, and when, with just a subpoena”

    People will read more into this than there actually is.

  10. Gustopher says:

    As Justice Sotomayer noted in her concurrence in the Jones case, though, that expectation of privacy has arguably changed significantly in an era where the devices that we still call “phones” are used for so many other purposes and are also broadcasting all kinds of personal information without our knowledge and beyond our control.

    “Expectation Of Privacy” is such a weird term to base things on. I am surprised that no one is making the argument that while the government scooping up information en masse might have been unconstitutional in the past, now that we have had revelations that the government is in fact doing that, we no longer have an expectation of privacy, and therefore this man’s records were lawfully obtained.

  11. mattbernius says:

    @James Joyner:
    I wasn’t kick on all cylinders when I initially replied and forgot the Court’s long history of having concurrences that had significantly different reasoning than the majority opinion. In retrospect I’m at a loss to answer your question.

    My only thought is that Gorsuch is so against keeping Smith and Miller as precedent that he wanted to punctuate it by dissenting from any opinion that went through them (versus concurring and still writing that they should be eliminated). Without reading the dissent, it feels a lot like style over substance.

  12. James Joyner says:

    @mattbernius: I didn’t go to law school but I took a lot of senior and graduate-level Conlaw, Admin Law, and the like in my undergrad and masters work (granted, 30 years ago). My recollection was that the whole point of concurrences was to agree with the outcome but not the reasoning. But there may be other reasons as well.

  13. OzarkHillbilly says:

    @James Joyner: @mattbernius: How’s about because he is just such a self important a-hole that to concur with lesser beings using faulty logic is beneath him? Seriously, the guy is just a pr!ck.

  14. Tyrell says:

    What if it is a suspected kidnapper and time is crucial to save a victim?
    I say act first, apologize later if necessary.
    “reasonable suspicion”

  15. Mike Schilling says:


    Gorsuch’s “dissent” (which looks a lot like a concurrence) is Living Constitutionalism. He’s willing to call your cell phone records your own property to make the 4th apply to them.

    Thomas’s dissent (which really is a dissent) insists that your cell phone records aren’t your property, so the 4th doesn’t apply, period.

    Yet another proof that originalism isn’t a system of reasoning; it’s a way of justifying decisions already made for other reasons.