Over 50 years ago, Charles Katz strolled into a phone booth on Sunset Boulevard in Los Angeles and placed a call to the East Coast, relaying gambling information on some college basketball games. Unbeknownst to Katz, the FBI had bugged the booth. And unbeknownst to either party, they’d walk hand-in-hand into legal history.
After he was convicted on the basis of that call, Katz challenged his conviction on Fourth Amendment grounds. That challenge eventually resulted in the landmark Supreme Court decision Katz v. United States, prompting the court to limit the kind of information law enforcement can get from phones without a warrant.
The fundamental strictures of the Fourth Amendment remain the same today as they were when Katz was decided in 1967 and generations before: The people must “be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures.” But ever since that fateful decision, courts have struggled to keep up with changing technology—and particularly communications technology, from the way we use our phones, to the amount and type of data available from phones and who gathers and has access to that data.
Wherever a man may be, he is entitled to know that he will remain free from unreasonable searches and seizures.
Justice Potter Stewart, Katz v. United States (1967)
And the amount of data our phones now gather has increased dramatically since the 1960s. Cell phones now constantly search for the nearest service towers, creating digital records that can give law enforcement a nearly constant record of an individual's movements and whereabouts.
In June, the Supreme Court extended privacy protections for cell phone users, ruling in Carpenter v. United States that police must obtain a warrant to get a phone's location information from cell towers.
Carpenter is an important decision not only for its ruling on cell-site location information, but because it marked a new and potentially significant acknowledgement by the Supreme Court: that the ever-increasing amount of data generated about individuals could require reshaping past doctrines for the digital age. Here’s how the explosion in data over the past half century factored into that decision, and what it means for legal practitioners.
Katz and a Reasonable Expectation of Privacy
Much of the legal arguments in Katz focused around where the government’s surveillance took place. Earlier Supreme Court decisions had held that “surveillance without any trespass and without the seizure of any material object fell outside the ambit of the Constitution” and therefore did not require a warrant. Indeed, the government argued that a public telephone booth was not a “constitutionally protected area.”
The Court in Katz rejected those arguments, finding that the Fourth Amendment “governs not only the seizure of tangible items, but extends as well to the recording of oral statements, overheard without any ‘technical trespass under...local property law,’” and “protects people—and not simply ‘areas’—against unreasonable searches and seizures”:
The Government's activities in electronically listening to and recording the petitioner's words violated the privacy upon which he justifiably relied while using the telephone booth, and thus constituted a "search and seizure" within the meaning of the Fourth Amendment. The fact that the electronic device employed to achieve that end did not happen to penetrate the wall of the booth can have no constitutional significance.
Important to the Court’s ruling was the information available to the government from its surveillance of the pay phone. The FBI was recording Katz’s conversations. (It should be noted that Justice Hugo Black’s dissent argued that the Fourth Amendment was not meant to protect personal privacy, but to protect "things" from physical search and seizure.)
And although the Supreme Court, in Olmstead v. United States, had found that “voluntary conversations secretly overheard” were not “persons, houses, papers, [or] effects,” subsequent rulings had eroded that view even before Katz. So eavesdropping on a conversation in a phone booth required a warrant.
Telephone users, in sum, typically know that they must convey numerical information to the phone company; that the phone company has facilities for recording this information; and that the phone company does in fact record this information for a variety of legitimate business purposes. Although subjective expectations cannot be scientifically gauged, it is too much to believe that telephone subscribers, under these circumstances, harbor any general expectation that the numbers they dial will remain secret.
Justice Harry Blackmun, Smith v. Maryland (1979)
The Third-Party Doctrine Scales Back Fourth Amendment Protections
Just twelve years later, the Court was dialing it back, so to speak, when it came to privacy on the phone. In Smith v. Maryland, police had requested, and a telephone company had provided, a pen register installed at the company’s central offices to record the numbers dialed from Michael Lee Smith’s home telephone. In this case, however, the Supreme Court decided that such monitoring did not constitute a search under the Fourth Amendment.
The Court conceded that an individual who “seeks to preserve something as private” generally has an expectation of privacy that is “one that society is prepared to recognize as reasonable.” But no person could have a reasonable expectation of privacy in information shared with third parties. And, given that telephone users consensually disclose the numbers dialed to the phone company as “a means of establishing communication,” the resulting business records are not entitled to Fourth Amendment protection.
Importantly for the Court in Smith, the pen registers involved “do not acquire the contents of communications.” As the Court explained, quoting United States v. New York Telephone Company (1977):
This Court recently noted: “Indeed, a law enforcement official could not even determine from the use of a pen register whether a communication existed. These devices do not hear sound. They disclose only the telephone numbers that have been dialed—a means of establishing communication. Neither the purport of any communication between the caller and the recipient of the call, their identities, nor whether the call was even completed is disclosed by pen registers.”
An off-site collection of data, voluntarily conveyed to a third party, is thus not a search and therefore requires no warrant. It sounds like an easy distinction from Katz.
Carpenter and the Evolution of Phone-Data Search & Seizures
Fast-forward almost 40 years, and the Supreme Court was again telling law enforcement they needed a warrant to obtain phone data, only this case more closely resembled Smith rather than Katz, at least at first blush. Police suspected that Timothy Carpenter had planned and served as a lookout in a series of armed robberies of electronics stores in the Detroit area. The FBI got access to his cell-site location information under the Stored Communications Act, obtaining 12,898 location points tracking Carpenter’s movements over 127 days—an average of 101 data points per day.
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.”
Chief Justice John Roberts, Carpenter v. United States (2018)
As an explainer, cell-site location information (CSLI) is a time-stamped record generated every time a cell phone connects to a set of radio antennas called cell sites, allowing it to make calls, send texts, or connect to the internet. When a person moves, that location changes, and can be loosely triangulated based on which cell sites the phone is connecting to.
Like Smith, law enforcement in this case obtained the information from the third-party phone company. The information was volunteered to the phone company as a way of establishing communication; the phone company records that information in the course of its business; and law enforcement could only see that the device had connected with a cell site—it had no access to the content of the defendant’s communications.
And yet, the Court decided that this intrusion went too far, just a few years after George Washington law professor Orin Kerr (who should know) was telling NPR that federal courts have consistently found that the location of your cellphone is unprotected by the Fourth Amendment. "So far, courts have applied the third-party rule across the board,” Kerr noted. “So as long as the information is disclosed to a third party, that's it.”
But that’s not it anymore, according to the Court, which in Carpenter ruled that “an individual maintains a legitimate expectation of privacy in the record of his physical movements as captured through CSLI,” and that the “location information obtained from Carpenter’s wireless carriers was the product of a search.” Thus, investigators were required to get a warrant before obtaining it.
Data Growth Forces Reconsideration of Established Doctrine
How did the justices distinguish this case from Smith? The “novel circumstances” and “unique nature of cell phone location records.” In essence, the staggering amount of data now available from just CSLI, which was not present in the pen registers of the 1970’s:
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 phrases “seismic shift in digital technology,” “nearly infallible” memory, and “exhaustive chronicle of location information” should ring alarm bells for any legal practitioner. The amount and type of data unavailable to the government in Carpenter without a warrant could swing any case, criminal or civil—and the Court's characterizations could apply to hundreds, even thousands, of technologies, not just CSLI.
From your average armed robbery to personal injury lawsuits, child custody and visitation disputes, and domestic violence protection order violations, data is increasingly becoming a key feature of successful litigation. In a recent case, for example, an expert witness painstakingly detailed a nine-point plan for extrapolating cell-site location information and testified to that information in court. Many attorneys would salivate at the prospect of having location data so “detailed, encyclopedic, and effortlessly compiled,” as the Court described.
But just because that data is there, doesn’t mean just anyone can access it. Fourth Amendment considerations, the Stored Communications Act, the demands of proportional discovery, and the limitations of review teams and technology, all create restrictions on what can be done with the immense amounts of data created today.
And while today’s Supreme Court is certainly no Warren Court when it comes to civil liberties, Chief Justice Roberts’ opinion in Carpenter indicates that the changing nature of technology could continue to make its mark on Constitutional interpretation. In the days and years ahead, courts, Supreme and otherwise, will no doubt continue to struggle to apply an 18th-century sentence to 21st-century technology via some 20th-century doctrines. It should be fun.