In a landmark victory for privacy rights, the Supreme Court today handed down a unanimous decision in Riley v. California mandating that police officers obtain a search warrant before examining the contents of an arrestee’s cell phone. The case arose in part after police officers in California arrested the defendant, Riley, for driving with expired registration tags. After searching through Riley’s cell phone, the police discovered photos and other data that incriminated Riley in a prior crime. Riley claimed the search of his cell phone constituted a violation of his Fourth Amendment right to be free from unreasonable searches and seizures. The Supreme Court agreed.

Chief Justice Roberts wrote the opinion, in which he highlighted the unique privacy concerns created by the modern technology of cell phones, particularly the vast data storage capabilities of “smart phones.” Although the Court has allowed police officers to search the body and immediate surrounding area of an arrestee without a warrant, the Chief Justice noted that “modern cell phones, as a category, implicate privacy concerns far beyond those implicated by the search of a cigarette pack, a wallet, or a purse.” Instead, cell phones, with their wealth of data, allow “the sum of an individual’s private life [to] be reconstructed through a thousand photographs labeled with dates, locations, and descriptions.”

The Chief Justice also stressed that the rationale given in previous rulings allowing warrantless searches of arrestees—to ensure officer safety and prevent the destruction of potential evidence—did not apply to the search of electronic data. In regards to officer safety, Roberts stated, “once an officer has secured a phone and eliminated any potential physical threats…data on the phone can endanger no one.” He also rejected the logic that officers need to employ warrantless searches to prevent the destruction of evidence by remote, third party data wiping. According to the Chief Justice, other, more practical, options for preserving the data remained open to police, such as turning the phone off or placing it in a signal-blocking bag.

Justice Alito delivered a concurring opinion, in which he stated that while he felt the ruling created “anomalies,” he did not see “a workable alternative.”  Given what he saw as the inability of the courts to develop a nuanced set of guidelines regarding searches of cell phones, he called on legislatures to take up the issue. It should be noted that the Maine state legislature is ahead of the curve on this issue, having enacted a law last year (supported by the ACLU of Maine) requiring law enforcement officials to get a warrant before accessing cell phone records.

In the end, the overwhelming privacy concerns associated with the search of cell phones seems to have animated the Court’s unanimous decision. The Chief Justice pointed out that whereas in the past searching a person’s pocket was profoundly different from searching a person’s home, today, if a person’s “pockets contain a cell phone…that is no longer true.” As such, the Supreme Court’s “answer to the question of what police must do before searching a cell phone…is accordingly simple—get a warrant.”