Carpenter v. United States

Supreme Court

Today, instead of a book review, I’m going to take a plunge into law review. I want to look at the decision of the United States Supreme Court in a case called Carpenter v. United States announced on June 22. This is a very important case about the privacy of your cell phone records.

If you’re interested in reading the full text of the Supreme Court’s decision, you can find it here. They might seem a little intimidating at first, but these legal decisions are really not hard to read. A few years ago I wrote this primer if you’d like an introduction.

The Case

This case is about a fellow named Timothy Carpenter who appears to have been the ring leader in a series of armed robberies in Michigan and Ohio in 2011. Police were able place him at the scenes of these crimes by obtaining phone company records of his mobile phone connecting to nearby cell towers. Based on these location records and other evidence, Carpenter was convicted and sentenced to over 100 years in jail.

Carpenter appealed on the grounds that the phone company location records had been obtained without a search warrant.

The Question

The central question which the Supreme Court had to decide in this case was: Can the Government trace your past movements by getting hold of phone company records collected from cell phone towers without a search warrant?

Legal Background

The requirement to get a search warrant comes from the Fourth Amendment to the Constitution. Here it is in full:

“The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.”

Now a search warrant is not always required. The police can search your person (pat you down) and your possessions at the time of arrest, for example, without a warrant. It is only when a search would be considered “unreasonable” that a warrant is required.

The courts have long recognized that the basic purpose of the Fourth Amendment is to “safeguard the privacy and security of individuals against arbitrary invasions by governmental officials.” Included in this interpretation is that the Fourth Amendment also protects individual’s expectations of privacy in many cases.

To make its decision, the Court reviewed two sets of previous cases involving the expectation of privacy. The first set concerned expectations about the privacy of your physical location and movements. When you take a walk outside, you’re in a public space. You could be seen by your neighbors, by shopkeepers, by passersby, even by police officers on routine patrol. Your walk isn’t private and you should have no expectations of it being private. On the other hand, if someone, especially the police, were to track your every movement for weeks on end, comprehensively recording the starting location, destination, time and duration of each trip, well that seems to cross a line into surveillance. Your expectations now are probably quite different.

The Court thinks so too. The Court has noted that new technologies like GPS have made this kind of surveillance easier, cheaper and far more precise and thus raise serious legal concerns about privacy.

The second line of cases concerns information about yourself that you choose to share with others. In general, if you share information with third parties, the Courts have ruled that you cannot have any expectation of privacy regarding that information.  This is known as the “third party doctrine.”  For example your bank statements, checks and deposit slips are shared with your bank and its employees and you can’t reasonably expect them to be private. So the police can demand these records from your bank with a subpoena, but they don’t need a warrant. In other words, your bank records are not protected by the Fourth Amendment. Similarly, the phone numbers you call are not protected because you have “shared” them with the phone company for purposes such as call routing and billing.

Your cell phone is constantly communicating with the wireless network — several times a minute in fact – to connect to different cell towers when you’re moving around, to check for email, to send and receive text messages, to retrieve social media updates, cat photos, etc. The phone company makes a timestamped record of each of these connections, called a Cell Site Location Information (CSLI) record. Taken together, these CSLI records form a detailed chronological history of your movements.

Do you voluntarily “share” this information with the phone company? After all, using a cell phone, taking it with you everywhere you go, leaving it on all the time, are all your choices. Can you really expect that information to remain private? Or does this kind of comprehensive recording of information constitute something different, something that is entitled to Fourth Amendment protection?

So the question in this case,

Can the Government trace your past movements by getting hold of phone company records collected from cell phone towers without a search warrant?

can be refined into a more precise legal question:

Do you have a reasonable expectation of the privacy of CSLI records collected by the phone company and are those records therefore entitled to protection under the Fourth Amendment?


In a few very quotable pages, Chief Justice John Roberts, writing for the majority, slices through these knotty issues.  He argues that technological developments now enable effortless, comprehensive collection of detailed and precise information about a person’s location and movements. This requires the Court to carefully consider whether or not to apply legal precedents.

“When confronting new concerns wrought by digital technology, this Court has been careful not to uncritically extend existing precedents.” [Opinion of the Court, p. 20]

In this case,

“A cell phone faithfully follows its owner beyond public thoroughfares and into private residences, doctor’s offices, political headquarters, and other potentially revealing locales.” [Opinion of the Court, p. 13]

This means,

“… 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.” [Opinion of the Court, p. 13]


“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.” [Opinion of the Court, p. 14]

But this position does not recognize the impact of new technologies.

“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.” [Opinion of the Court, p. 15]

Furthermore, cell phone users really have no choice about whether or not they share all this data.

“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.” [Opinion of the Court, p. 17]

Which leads to this conclusion:

“Before compelling a wireless carrier to turn over a subscriber’s CSLI, the Government’s obligation is a familiar one—get a warrant.” [Opinion of the Court, p. 19]

“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.” [Opinion of the Court, p. 22]

Decision & Dissents

The Supreme Court reversed the decision of the Appeals Court, and sent the case back to the lower Courts for re-consideration. The cell phone location information collected by the police without a warrant is now inadmissible evidence. I don’t know whether this means Carpenter’s convictions will be thrown out, or if he will be tried again without the cell phone location information being used as evidence against him. Regardless, Carpenter won his appeal.

This case was decided by a 5-4 majority, with Justices Breyer, Ginsberg, Kagan, and Sotomayor supporting Chief Justice Roberts.  Justices Alito, Gorsuch, Kennedy and Thomas disagreed and each of them wrote individual dissenting opinions.

Justice Kennedy contends that cell-site records are no different than any other business records which the government already has the right to compel (via subpoena) third parties to release.

Justice Thomas noted that the cell-site records did not belong to Carpenter, they belonged to the wireless carriers. He maintains the Fourth Amendment doesn’t apply here because none of Carpenter’s “houses, papers, and effects” were searched.

Justice Alito agrees with Thomas that the records in question belong to the phone company and not to Carpenter. He further argues that there’s a significant distinction between the government sending its agents (i.e. the police) into a person’s house to search through their papers and an order that simply requires a third party to search through and produce some of its own documents.

Justice Gorsuch, the newest member of the Court, makes the most interesting, and the most entertaining dissent. He argues that the legal precedents in this case are a mess and that their conclusions about our expectations of privacy related to Fourth Amendment claims are so flawed and ill-defined as to be useless, resulting in “unpredictable— and sometimes unbelievable—jurisprudence.”

“Take Florida v. Riley, 488 U. S. 445 (1989), which says that a police helicopter hovering 400 feet above a person’s property invades no reasonable expectation of privacy. Try that one out on your neighbors.” [Gorsuch dissent, p. 9]

He also argues that just because a third party holds information about you, that doesn’t necessarily mean you should have no reasonable expectation of privacy, let alone that you have relinquished all Fourth Amendment rights. I get the sense that Gorsuch was sympathetic to Carpenter’s appeal and might have sided with the majority if their rationale had been different, or if Carpenter has made his appeal on different grounds.

Unsolicited Feedback

The judgement in this case is a victory for individual privacy.  (It’s also a bright spot in an otherwise dismal term in which the Supreme Court term upheld President Trump’s travel ban in Trump v. Hawaii.)

You might not like the fact that a convicted felon like Timothy Carpenter could be let off the hook on a “technicality”, but the technicality here involves our precious and rapidly eroding privacy. So much of the information we create and collect, and that is created and collected about us, is now held by third parties. Our “papers and effects” are no longer just physical objects and are very often not in our direct possession. Short of swearing off modern technological advancements like cell phones and GPS, it’s virtually impossible to prevent third parties from accumulating vast amounts of information about us. In my view this means we have a greater interest than ever in the privacy of the data about us that is collected and stored by third parties. Our expectations about the privacy of that information are just as worthy of protection as the physical papers we keep at home.

So I think it’s gratifying and appropriate that the Supreme Court recognizes that technological developments require the courts to re-think previous legal precedents, and not to apply them blindly. It’s good to see the Court grapple with the implication of new technologies and come to novel conclusions.

That said, I think Justice Gorsuch raises some interesting and valid concerns about the muddled state of the legal precedents in this area, especially around the third party doctrine.  It seems the Court has more work to do here.

One final note: I’m starting to think that Chief Justice John Roberts has a special interest in the intersection of technology and privacy. This is the second time I’m aware of where he has written the majority opinion in a case involving cell phones and privacy rights. The first was Riley v. California in which the Supreme Court decided unanimously that the police require a warrant to search the information stored on your cell phone. (My review here.) It will be interesting to see if he continues to take such an active role in future cases in this area

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