Is It Unreasonable to Expect Cellphone Privacy?

A case that comes before the Supreme Court Wednesday may erode or solidify Justice Antonin Scalia’s legacy. How the justices decide in Carpenter v. U.S. won’t matter as much as how they reason. If they use the “reasonable expectation of privacy” test to decide whether the government can access cellphone users’ location data without a warrant, Scalia’s contributions to Fourth Amendment jurisprudence will be negated. But if the high court recognizes that data as owned in part by cellphone users, Scalia’s legacy will be secured, along with the Constitution’s safeguards against unreasonable search and seizure.

The plaintiff, Timothy Ivory Carpenter, was convicted in 2014 of participating in a string of armed robberies in the Detroit area and sentenced to 116 years in federal prison. Investigators obtained court orders netting 127 days of Mr. Carpenter’s cellphone records, showing that his phone was in communication with cell towers near the sites of four robberies. The court will decide whether investigators should have gained access to that data under a relatively low statutory standard requiring that the information be “relevant” to an ongoing investigation, or whether they should have asked a court for a warrant based on probable cause.

Since 1963, the dominant approach to the Fourth Amendment has been derived from a solo concurrence in Katz v. U.S. setting out the reasonable-expectation-of-privacy test. That test defines a search as having occurred anytime a government agent violates a defendant’s reasonable privacy expectations. It has often operated as a one-way ratchet against Fourth Amendment protection, using curious logic.

Because possession of drugs and other contraband is illegal, concealing them is unreasonable. Thus, courts have held that whatever government action turns up such contraband is not a search. Actions that most would consider searches, such as directing drug-sniffing dogs at people and flying planes low over suspects’ houses, are treated as nonsearches that don’t require warrants.

Smith v. Maryland (1979) is the premier precedent supporting government access to telecommunications data. In Smith, government agents acting without a warrant persuaded a Baltimore telephone company to place a pen register on the phone line of a burglary-and-stalking suspect. The device captured the numbers of his outgoing calls, showing that he had dialed the victim’s home number. The Supreme Court found there was no reasonable expectation of privacy and thus no seizure or search.

Today the government interprets Smith as providing warrantless access to troves of data about the locations and movements of every cellphone user, subject to that statutory relevance standard. That data can reveal sensitive information, such as when people seek medical or psychological treatment, where they go to church, their relationships and business dealings, attendance at political events, and more. The appeals court in Carpenter adopted Smith’s reasoning.

For years, Scalia pointedly avoided the reasonable-expectation-of-privacy test. His 2001 decision in Kyllo v. U.S., for example, addressed the use of a thermal imaging device to detect heat patterns emanating from a home thought to contain a marijuana-growing operation. Scalia didn’t refer to privacy expectations in his argument. Rather, he claimed that when government agents use an exotic device “to explore the details of the home that would previously have been unknowable without physical intrusion, the surveillance is a ‘search’ and is presumptively unreasonable without a warrant.”

In 2012, another major Scalia decision again steered around the potholed logic of “reasonable expectations.” In U.S. v. Jones, Scalia’s majority opinion found that attaching a Global Positioning System device to a car without a warrant, and using that device to monitor the vehicle’s movements, constitutes a search. In 2015, the Second U.S. Circuit Court of Appeals in New York polished Scalia’s logic. Attachment of the GPS device was “a technical trespass on the defendant’s vehicle”—a small but important seizure that put the car to the government’s purposes.

Gauzy appeals to privacy expectations only complicate what ought to be straightforward: Searching is searching; seizing is seizing.

Cellphone privacy policies give consumers many rights to control their telecommunications data. Essentially these are property rights, which on their own should require that the government obtain a warrant before searching and seizing digital records. In Carpenter the court may find that such contracts help create an “expectation of privacy.” Or it may find that there isn’t a reasonable privacy expectation. Seizing data and examining its contents would become neither seizure nor search, giving government agents a free hand.

That kind of illogic would be a loss for Justice Scalia’s legacy. The court should find that telecommunications data are owned in part by cellphone users. A warrant is required for the government to take such property and examine it.

Originally published to Wall Street Journal.