The Supreme Court this week agreed to decide whether police must demonstrate probable cause that a crime has occurred before obtaining a suspect's cellphone records. That might seem like a narrow question about police procedure. But if the justices think boldly, they can use this case to redefine the 4th Amendment's protection against unreasonable searches and seizures for a society in which technology has transformed traditional notions of privacy.
Timothy Carpenter was convicted of committing nine armed robberies in the Detroit area, partly on evidence investigators obtained from mobile phone networks showing that he made calls using towers near the robbery sites. The prosecutor told the jury that Carpenter was "right where the first robbery was at the exact time of the robbery, the exact sector."
Carpenter's number was among those obtained by the FBI from an admitted member of a robbery ring. Agents obtained data about Carpenter's calling history and location from his wireless provider not with a warrant based on probable cause, but with a federal magistrate's order based on the lesser standard — contained in the federal Stored Communications Act — that the government had "reasonable grounds" for believing that the records were "relevant and material to an ongoing investigation."
The U.S. 6th Circuit Court of Appeals upheld Carpenter's conviction on the grounds that the acquisition of the incriminating records wasn't a "search" under the 4th Amendment, and it cited an oft-invoked 1979 Supreme Court decision to conclude that Carpenter had no reasonable expectation of privacy. In that case, Smith vs. Maryland, the court upheld the use without a warrant of a device called a "pen register" to track the telephone numbers a suspected criminal called — information, the court said, that a customer voluntarily shares with the phone company.
The appeals court also said that the records showing the locations where Carpenter's cellphone connected with a mobile phone network were not his property but "business records obtained from a third party, which can only diminish the defendants' expectation of privacy in the information those records contain."
The appeals court accurately stated longstanding 4th Amendment doctrine — but that's precisely the problem. The Supreme Court's interpretations of "reasonable expectation of privacy," "business records" and "third-party information" haven't kept up with technological developments — and some of the justices have admitted as much.
In a 2012 case, Justice Sonia Sotomayor noted in a concurring opinion that in the digital age, "people reveal a great deal of information about themselves to third parties in the course of carrying out mundane tasks." It's not just the phone numbers of the people they contact that can be disclosed, Sotomayor wrote, but far more personal material, such as the Web pages they visit and "the books, groceries, and medications they purchase" online.
The revealing nature of these data is what's key here. It's why the information collected looks less like lists of transactions and more like the content of communications, which falls clearly within the 4th Amendment's umbrella.
That same year Chief Justice John G. Roberts told a university audience that the challenge for the court for the next 50 years would be: "How do we adapt old, established rules to new technology?"
Roberts was the author of the majority opinion in a 2014 case in which the court ruled unanimously that police generally may not, without a warrant, search digital information on a cellphone seized from someone who has been arrested. Cellphones, Roberts wrote, "hold for many Americans the privacies of life. The fact that technology now allows an individual to carry such information in his hand does not make the information any less worthy of the protection for which the Founders fought."
In the same opinion, Roberts noted that, while some information is contained on a phone itself, other information is stored on servers online. That's another way of pointing out that highly personal information that an individual considers private may still be in the "possession" of a communication company.
The law — including the interpretation of what constitutes an "unreasonable search and seizure" — should reflect such realities. The Carpenter case gives the court a chance to bring the 4th Amendment into the 21st century.