In 2012, Chief Justice John G. Roberts Jr. told a university audience that the challenge for the Supreme Court for the next 50 years would be: "How do we adapt old, established rules to new technology?" On Wednesday, the court proved itself equal to that challenge in at least one context. It ruled unanimously that, except in extraordinary cases, police must obtain a warrant before searching the contents of an arrested person's cellphone.
This is a historic decision because allowing police to sift through the contents of a modern smartphone gives them access to a wealth of information about a person's most private and personal affairs, from emails to family photos to bank statements. As Roberts wrote in his magisterial majority opinion: "With all they contain and all they may reveal, [cellphones] hold for many Americans 'the privacies of life.'"
In the case of David L. Riley, a San Diego man arrested on weapons charges, those privacies included a photograph police found on his phone showing him in front of a car used in a drive-by shooting. Riley was eventually convicted of attempted murder.
You don't need a law degree to believe that allowing police to search through a cellphone without a warrant is an "unreasonable search" of the kind prohibited by the 4th Amendment. But to reach that conclusion, Roberts had to wrestle with a 1973 decision that gave police wide discretion to search people they arrested — including packages in their pockets — even if the search wasn't necessary to disarm the suspect or prevent the destruction of evidence.
Rather than overruling that decision, Roberts declined to extend its reasoning to cellphones, which contain the sort of records that would have been stored in private homes at the time the Bill of Rights was adopted. "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," Roberts wrote.
Wednesday's decision also raises the possibility that the court might be willing to revise another precedent. In 1979, the justices upheld the warrantless tracking of phone numbers dialed by a criminal suspect, on the grounds that no one has a reasonable expectation of privacy in information they turn over to a third party, such as a phone company. That precedent has been cited to uphold the constitutionality of the National Security Agency's bulk collection of Americans' telephone records.