Constitution Check: Does cellphone privacy follow its owner’s wanderings?

Lyle Denniston, the National Constitution Center’s constitutional literacy adviser, examines a case that has just arrived at the Supreme Court about police access to cellphone location data stored on cellphone towers.



“As technology advances, location information from cellphones (and, of course, smartphones) will undoubtedly become more precise and easier to obtain, and if there is no expectation of privacy here, I have some concerns about the government being able to conduct 24/7 electronic tracking (live or historical) in the years to come without an appropriate judicial order. And I do not think I am alone in this respect.”

– Excerpt from an opinion by a federal judge, Adalberto Jordan of the U.S. Court of Appeals for the Eleventh Circuit, limiting his support for a ruling by that court rejecting a Florida man’s Fourth Amendment challenge to federal investigators’ monitoring of the places where he used a cellphone over a continuous span of more than two months. That individual has now filed an appeal at the Supreme Court.


For nearly a half-century, it has been true that a private individual carries around as a kind of personal constitutional shield a right of privacy. As the Supreme Court put it in a famous decision in 1967, “wherever a man may be, he is entitled to know that he will remain free from unreasonable searches and seizures.” All that is necessary to have that shield available as that individual moves about, the court said then, is that he or she is doing something that they personally regard as private, and that society in general would agree that it should be private.

In technical constitutional terms, that decision in Katz v. United States – extending protection to what an individual said while using a public telephone booth – was the origin of the idea that the Fourth Amendment protects “a reasonable expectation of privacy.” That amendment, the court said, “protects people, not places.”

In the case of the telephone booth, the caller may have been entirely visible through the glass doors, but was still expecting that the actual messages spoken into the telephone were meant to be heard only by the person on the other end.

It is too much to say, however, that the individual never loses that privacy once the activity moves outside the enclave of the home into the larger world. The catch is that part of the test that says society must share the perception that the activity does deserve to remain private. Even in that 1967 ruling, the court was careful to say that “what a person knowingly exposes to the public, even in his own home or office, is not a subject of Fourth Amendment protection.”

That, of course, makes the protection of that amendment depend in part on the specific action the individual takes to show that the activity was meant to be private – such as closing the door on the telephone booth.

Complicating the constitutional question, however, is the situation when an individual tries to keep something private, but strangers (“third parties,” in the language of law) learn of that activity. That was the scenario that the Supreme Court encountered in 1979, when it allowed law enforcement officers to obtain from a telephone company the numbers that a user had dialed.

That, the Justices ruled in the case of Smith v. Maryland, was not even a search under the Fourth Amendment, because the individual gave up the privacy about those numbers merely by dialing; that allowed a record to be made in the files of the company. Besides, the court added, the officers did not learn much from that data; they could not even be sure that any call actually had connected.

Lately, though, that part of Fourth Amendment law is being reexamined in the courts, as changes in technology make it far more likely that a person’s activities in public can be tracked much more closely, and thus more intrusively.

Three years ago, the Supreme Court for the first time examined what it means to privacy that police can use a tracking device, linked to globe-circling satellites, to trace the movement of a suspect’s car, and thus some of the activities of the car’s driver. The decision in Jones v. United States was limited, based on a theory that installation of the device was a “trespass,” but it has come to stand for two larger principles: first, that officers should get a warrant before they do such monitoring, and, second, that technology can definitely change the Fourth Amendment equation about what is private.

Last year, the court went further in this examination, concluding that police should get a warrant before they check out the stored contents of a cellphone that police take away from an individual they have arrested. What is logged on a cellphone, the Justices said, can include a vast amount of intensely personal data, and police access to that should only be allowed if a judge has found a good reason to issue a search warrant to get at it.

The next step in this constitutional evolution has just arrived in an appeal to the Supreme Court, in the case of Davis v. United States. It is a test of the privacy – or lack of it – of the information that police may gather by checking stored data on cellphone towers located around a community. The majority of the U.S. Court of Appeals for the Eleventh Circuit decided that this did not even implicate the Fourth Amendment, because an individual has no “reasonable expectation of privacy” in the location data; that is a record kept by the tower operator, the telephone company, and the individual whose calls were logged gave it up merely by using his cellphone.

The data, covering 67 continuous days of use on that cellphone, was technically so refined and detailed that it actually placed the user – Quartavius Davis – at the scene of a series of robberies of local businesses in the Miami, Fla., area. Davis’s lawyers have calculated that the towers yielded more than 11,000 bits of data about where he was when he made or got a call. The data was used to convict him of a series of federal crimes, and his lawyers failed to get that excluded from his case on a theory that it invaded his right of privacy in his movements, so should have been barred unless police had a search warrant.

Taking that case on to the Supreme Court, his attorneys argued that the Justices needed to step in now “to ensure that the Fourth Amendment does not become a dead letter as police accelerate their warrantless access to rich troves of sensitive personal location data.”

The court is expected to act on the case early in the next term.

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