Supreme Court Accepts Fourth Amendment Case Involving Location Tracking Of Your Smartphone

Yesterday, the Supreme Court accepted a case that will determine whether the Fourth Amendment allows law enforcement to obtain location data without a search warrant.


Yesterday, the Supreme Court agreed to hear a case regarding whether or not law enforcement officials should be required to obtain a warrant before accessing phone tracking data from cellphone companies:

WASHINGTON — The Supreme Court agreed on Monday to decide whether the government needs a warrant to obtain information from cellphone companies showing their customers’ locations.

The Supreme Court has limited the government’s ability to use GPS devices to track suspects’ movements, and it has required a warrant to search cellphones.

The new case, Carpenter v. United States, No. 16-402, concerns historical data held by cellphone companies that shows users’ movements over time and could, for instance, place them at the scene of a crime.

In 1979, in Smith v. Maryland, the Supreme Court ruled that a robbery suspect had no reasonable expectation that his right to privacy extended to the numbers dialed from his phone. The court reasoned that the suspect had voluntarily turned over that information to a third party: the phone company.

Relying on the Smith decision’s “third-party doctrine,” federal appeals courts have said that government investigators seeking data from cellphone companies showing users’ movements do not require a warrant.

A federal law, the Stored Communications Act, does require prosecutors to go to court to obtain tracking data, but the showing they must make under the law is not probable cause, the standard for a warrant. Instead, they must demonstrate only that there were “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.”

In rejecting the argument that the relaxed standard violated the Fourth Amendment, which bans unreasonable searches, the United States Court of Appeals for the Fourth Circuit, in Richmond, Va., for instance, said it was bound by the Supreme Court’s ruling in the Smith case.

Given the Court’s 1979 ruling in the aforementioned Smith v. Maryland case, it’s not entirely surprising that the lower courts rejected the Defendant’s argument and found that police did not need a warrant to track him in the manner that they did. In that case, the Court relied on an idea that had been established in previous Fourth Amendment cases, specifically that there generally was not a requirement for a warrant to obtain information, documents, or things that are in the custody of a third party no matter how much that may undermine the privacy of a Defendant or potential suspect. This was chiefly because of the fact that the Court found that the individual making the claim of a Fourth Amendment violation because they did not have a reasonable expectation of privacy in material that was in the custody and control of a third party. There are some exceptions to that rule, but they generally depend on the individual have some degree of control over the information in question. For example, a safe deposit box in a bank’s vault can generally only be accessed by law enforcement if they obtain the court order, typically via a search warrant based on probable cause that identifies specific documents or things they expect to find in the box in question. In that case, though, it’s generally the rule that only the box owner or a designated representative can obtain access to a safe deposit box and then they must have a key that would allow them to open the box.

The calling data that was at issue in Smith, on the other hand, is not something that the customer of a phone company has any degree of control over and neither, law enforcement argued successfully below in the Carpenter case, is the tracking data that is at issue in the case the Court has now accepted for appeal. Because of this, the Court will be required in this case to determine the extent to which Smith remains good law and the extent to which the third-party rule must be adapted to fit a new world where the concept of what is and is not considered a “reasonable expectation of privacy” has changed significantly in the light of technological advances in the thirty-eight years since Smith was decided.

Amy Howe at SCOTUSBlog has more:

Carpenter argued that the records should be suppressed because the government had not obtained a warrant for them. The district court denied that request, however, and Carpenter was convicted on 11 of the 12 counts for which he was indicted. On appeal, the U.S. Court of Appeals for the 6th Circuit upheld Carpenter’s convictions. It too rejected Carpenter’s arguments that disclosure of his phone records to the federal government was a “search” for which the government needed a warrant. The court of appeals reasoned that cellphone companies had collected the data “in the ordinary course of business” for their own purposes – including “to find weak spots in their network and determine whether roaming charges apply.” And Carpenter would have no reason to believe that his cellphone records would be kept private, the court explained, because the records simply show where his phone connected with cell towers, without providing any information about the content of his calls.

Urging the justices to deny review, the federal government pointed to two of the Supreme Court’s decisions from the 1970s, which held that obtaining a business’ records about a particular person does not rise to the level of a “search” of that person, for which a warrant would be required, even if the records contain information about the person. And although the records at issue in those cases consisted of bank accounts and a list of the numbers that the defendant dialed on his home phone, it shouldn’t matter, in the government’s view, that Carpenter’s case involves “new technologies” like cellphones.

But today’s announcement that the Supreme Court will review Carpenter’s case may signal that the justices – all of whom presumably carry cellphones themselves – might view the issue differently. Three years ago, the court ruled that police must get a warrant to look at information stored on the cellphone of someone who has been arrested. In reaching that conclusion, Chief Justice John Roberts observed that today’s phones are “based on technology nearly inconceivable just a few decades ago” and “are now such a pervasive and insistent part of daily life that the proverbial visitor from Mars might conclude they were an important feature of human anatomy.” Moreover, the justices stressed in that opinion, they were not holding that “the information on a cell phone is immune from search” but instead simply making clear that “a warrant is generally required before such a search.” The justices may ultimately conclude that, as the federal government urges, giving police access to Carpenter’s historical cell-site data is significantly less intrusive than giving them access to the kind of “detailed personal facts” available on a cellphone itself. But, even if so, they may also believe that, at a minimum, this area of the law needs to be updated and clarified for the 21st century.

And Orrin Kerr at The Volokh Conspiracy explains why this case is so important:

The Carpenter case is tremendously important, I think. The structure of modern surveillance law is built on the idea that the contents of communications receive Fourth Amendment protection but that non-content metadata — records about communications, and other third-party business records — do not. That has been the rule since the 19th century for postal letters, and it has been the rule since 1979 for phone calls. Carpenter will help determine if that basic rule framework will remain, or if the Supreme Court will amend it somewhat or even dramatically change it.

Part of the importance of the case is that it’s not just about cell-site records. Although the case is formally about cell-site records, it’s really about where to draw lines in terms of what network surveillance triggers the Fourth Amendment and how the Fourth Amendment applies. The justices can’t answer how the Fourth Amendment applies to cell-site records without providing a framework for how the Fourth Amendment applies to many other forms of surveillance, such as visual surveillance, obtaining traditional phone records, obtaining e-mail transactional records, obtaining credit card records and the like.


[T]he justices will have two questions: what a search is, and when searches are reasonable. Most will focus on the first question, but note that the two issues go together. As I explained here, the broader the court interprets “search,” the more pressure there is to water down reasonableness. The narrower the definition of “search,” the stronger the reasonableness standard tends to be. This creates some interesting dynamics. For example, you might get a ruling that there is no search but that retains the traditional default warrant rule for searches. On the other hand, you might get a ruling that a search occurred but that authorizes a new category of warrantless surveillance. This is just speculation, of course, but I suspect the briefing will urge major doctrinal innovations on both questions.

While the rulings in the District Court and the Court of Appeals in Carpenter were governed by the Supreme Court’s ruling in Smith v. Maryland, the Supreme Court is not necessarily constrained by that ruling. Instead, it will be required to determine the extent to which that holding can still apply in this modern world. This, after all, a world in which nearly everyone is carrying a phone capable of being tracked anywhere in the world via both cell tower location data. If that phone is a smartphone, it can also be tracked when the phone in question is reporting its location by accessing Global Positioning System satellites for the many applications that make use of such data.

While it was likely true that the average American in 1979 didn’t have any real expectation that the number they call using a landline phone is something that should be considered private, that’s not necessarily true anymore. Most smartphones, for example, allow users to control what applications can and cannot access the location data on their phones  In this world, it’s like that many if not most Americans would expect that something as detailed as where they are at any given point in time would be something that should be kept private regardless of the fact that a third-party such as a telecommunications provider stores such information in their computer systems. Because of these changing privacy expectations, there is a good argument that the “third-party” doctrine established in Smith cannot be reasonably applied to the modern world and that some new rule is required.

As Damon Root notes at Reason, Justice Sonia Sotomayor recognized this reality in a concurring opinion in a 2012 case called United States v. Jones. In that case, the Court ruled in a unanimous ruling where the Justices disagreed on the reasoning behind the decision that police must obtain a warrant in order surreptitiously attach a GPS device to a suspect’s vehicle for the purpose of tracking their movements. In her concurrence, in that case, Justice Sotomayor took particular note of the changing expectations of privacy since the Smith case was decided:

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

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

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

Justice Samuel Alito also noted the role that changes in technology may have changed what constitutes a reasonable expectation of privacy:

Recent years have seen the emergence of many new devices that permit the monitoring of a person’s movements. In some locales, closed-circuit television video monitoring is becoming ubiquitous. On toll roads, automatic toll collection systems create a precise record of the movements of motorists who choose to make use of that convenience. Many motorists purchase cars that are equipped with devices that permit a central station to ascertain the car’s location at any time so that roadside assistance may be provided if needed and the car may be found if it is stolen.Perhaps most significant, cell phones and other wireless devices now permit wireless carriers to track and record the location of users–and as of June 2011, it has been reported, there were more than 322 million wireless devices in use in the United States.8 For older phones, the accuracy of the location information depends on the

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

In the pre-computer age, the greatest protections of privacy were neither constitutional nor statutory, but practical. Traditional surveillance for any extended period of time was difficult and costly and therefore rarely undertaken. The surveillance at issue in this case–constant monitoring of the location of a vehicle for four weeks–would have required a large team of agents, multiple vehicles, and perhaps aerial assistance.10 Only an investigation of unusual importance could have justified such an expenditure of law enforcement resources. Devices like the one used in the present case, however, make long-term monitoring relatively easy and cheap.

Alito goes on to note that the Court’s case law on the Fourth Amendment may not be well-suited in determining where the line should be drawn in the light of new technology, and notes that the ideal solution would be for Congress or other legislative bodies such as state legislatures to draw those lines. So far, though, there’s been little to no legislative action on issues such as this, which is why it will now fall to the Court to determine the extent to which decades old decisions based on a different kind of technology can be applied to the modern world.

Jazz Shaw at Hot Air comes at this issue from a very different perspective, arguing that the Court should not be acting in a manner that would limit the ability of law enforcement to do its job:

If they were handing the police recordings of your conversations it would be another matter, but this data only covers your location when you are on the move. (Again, out in the public square.) The third party provider is relaying data which equates to the tower observing you, with your phone, passing some specific location. If a local shopkeeper observed you pulling up in your car in front of his store and testified to that fact in court would they be invading your privacy? Certainly not.

In the end, this comes down to yet another question of whether or not the courts will allow law enforcement to be hampered in collecting even the most basic, generic information when attempting to solve and prosecute a criminal case. Extending the definition of the wording of the Fourth Amendment in this fashion does nothing to promote the “privacy” of anyone except those seeking to evade conviction for crimes they actually committed. It also does nothing to protect the public from those who would break the law.

It is certainly the case that in considering cases such as this, courts do need to balance the concerns about individual privacy and the need for law enforcement to do its job of protecting the public. Rulings that unduly restrict the police should probably be avoided when possible. At the same time, though, the Fourth Amendment makes clear that there are times when the needs of law enforcement must be put to the side in favor of individual rights and the expectations that Americans have that they will have a certain level of protection in the privacy of their “persons, houses, papers, and effects” must be protected. As it stands, the protection that the Fourth Amendment provides is a very simple one and it says that police can have access to such information and material when they can prove to a Court that they have probable cause to believe that a crime has been committed or that the information sought will lead to relevant evidence in a criminal investigation or court proceeding.

This isn’t “hamstringing” law enforcement in any sense of the word. Instead, what it does is give the public protection from law enforcement being able to obtain information about them on a mere whim. Additionally, extending the requirement for a warrant in cases like Carpenter doesn’t just protect people who may or may not have committed a crime. It protects all of us from a world where the government could theoretically track anyone it wants, for any reason, simply by demanding that a telecommunications provider hand over certain data. The fact that it also protects the rights of those suspected of having committed a crime is a feature, not a bug, and it goes to the heart of why the Fourth Amendment exists in the first place.

In any event, this case will not be briefed and argued until the next term of the Court begins in October, but it is already clear that it will be among the most important Fourth Amendment cases the Court has dealt with in quite some time. We should all be keeping an eye on this case because, for better or worse, the outcome will have an impact on all of us.


FILED UNDER: Law and the Courts, Policing, Science & Technology, US Politics, , , , , , , , , , , , , , , , ,
Doug Mataconis
About Doug Mataconis
Doug Mataconis held 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 and contributed a staggering 16,483 posts before his retirement in January 2020. He passed far too young in July 2021.


  1. Pch101 says:

    Smith v. Maryland was an unfortunate decision because it effectively allows privatization to be used as an end run around our privacy rights.

    I suspect that one of the goals of dismantling net neutrality is to make it possible for the government to locate and silence its critics by simply buying the information. Your ISP can essentially sell you off to any company or government agency that wants to know about you.

  2. teve tory says:

    Bruce Schneier makes the point that government powers that are acceptable in a low-tech world take a different character in a high-tech world.

    Let’s say the police are following you without a warrant because they think you’re up to something. You don’t have a right not to be followed. In a computerless world, there are constraints which cause the cops to generally only do this when they really have a reason to think you’re a bad guy. So the cops will wind up possessing a few notes about where a few people were on a few days. Most of us are okay with that. Not terribly susceptible to abuse.

    Now throw computers and GPS into the mix. Now cops can follow everyone all the time. They can amass records of what everyone is doing, where they’re doing it, all the time. The cops wind up possessing complete notes about where every person was at every moment. Legally, there’s not much difference, is there? They’re still just following a person. There’s no right not to be followed. But practically speaking, that is 150 bajillion times more susceptible to abuse.

  3. Daryl's other brother Darryl says:

    I’d like to see the lower courts decision over-turned…but just the same…there is no rule that says you cannot turn your phone off…or just leave the figgin’ thing at home.

  4. Mr Bluster says:

    Good advice from OTB to Donald Trump!

    …turn your phone off…

    Seconded by Jeff Sessions, Bob Corker, Rex Tillerson and
    Dana Shell Smith, US Envoy to Qatar.

  5. Franklin says:

    @Daryl’s other brother Darryl: I don’t know if this is still true, but before the smart phone rage, most cell phones would still ping towers even when they were supposedly “off”. You would actually have to remove the battery to prevent tracking. (Some mobsters learned this the hard way.)

    Furthermore, all phones still track you when you are in private locations, so the argument that this is already public data is not quite true.

  6. JohnMcC says:

    I’ll start with a confession that I have a strong distaste for many of the changes that digital technology has wrought. And one is having someone stroll by me in a store chattering busily into some blue tooth or such inflicting their relationship with it’s emotional ups and downs on me. If I understand what is being proposed, you are saying that that person should be presumed to have strong privacy rights to an interaction that they just insisted that I witness against my will.

    If deposed I would be required to report and repeat as much of that conversation as I was given against my will. But you’d keep the remainder and even the fact that this person was in the WinnDixie at a specific time from a prosecutor, eh?

    What a stupid world.

  7. Matt says:

    @Daryl’s other brother Darryl: Even if you turn it off you are still tracked. You have to pull the battery and possibly the sim card if you really don’t want to be tracked.

    The NSA has proven tech to wake your phone remotely as long as it has a battery in it.

  8. Mr Bluster says:

    …but this data only covers your location when you are on the move. (Again, out in the public square.)

    So if I am inside my house I am entitled to some privacy?
    Or do I need to line my ceiling with tin foil?

  9. Grumpy Realist says:

    Time to start carrying around passenger pigeons for communications, methinks.

  10. Tyrell says:

    In some cases the police need to track someone who may be a kidnap victim. They do not always have time to get a warrant.

  11. Franklin says:

    @Tyrell: And that’s fine, but I doubt that the 4th Amendment is pertinent in that case. A kidnap victim isn’t the target of an investigation. It would be like saying a policeman can’t look for identification on a murder victim because it’s an illegal search.

    The only real penalty for violating the 4th Amendment is that any evidence gathered illegally from a subject can’t be used against the subject in a court of law. The kidnappee is a different subject than the kidnapper.

  12. Just 'nutha ig'nint cracker says:

    @Pch101: ISPs have always been able to sell you to whomever they wanted to. It was one of the first things that I noticed when I read my first TOS from Yahoo. What’s happening now is that government and business are trying to hobble the few small concessions that ISPs made to their customer/users product line to avoid erosion.