The most important privacy ruling in over 40 years

The Supreme Court made history this week by holding that, when the police find a cell phone on an arrestee, they must get a warrant before searching the data on that phone.

For the past 45 years, under the "search incident to arrest" doctrine, the Supreme Court rule has been that everything within reach of an arrestee can be seized and searched without the need for a warrant, or even probable cause. If the police found a sealed package in the pocket of an arrestee, they could open that package. The old rule was assumed that it was "a totally different thing to search a man's pockets and use against him what they contain, from ransacking his house for everything which may incriminate him." Today's ruling, written by Chief Justice Roberts, held that different rules must apply to modern cell phones, because "a cell phone search would typically expose to the government far more than the most exhaustive search of a house."

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This decision is not merely about cell-phone privacy, it is about the privacy rules that govern digital data. Fifty years from now, future generations will look back on Riley v. California as the case that established privacy rights in the digital age. As Chief Justice Roberts closed his opinion:

"Modern cell phones are not just another technological convenience. With all they contain and all they may reveal, they hold for many Americans "the privacies of life," Boyd, supra, at 630. 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. Our answer to the question of what police must do before searching a cell phone seized incident to an arrest is accordingly simple — get a warrant."

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Cell phones have quickly become indispensable to Americans. Over 90 percent of Americans own a cell phone, over 75 percent of Americans keep their phone within 5 feet at all times and 12 percent of Americans even bring their phones into the shower. A modern smart phone is not merely a phone, it has replaced "cameras, video players, rolodexes, calendars, tape recorders, libraries, diaries, albums, televisions, maps, or newspapers." A smart phone with GPS literally records every movement of its owner. It stores "every piece of mail … received for the past several months, every picture … taken or every book or article … read."

Chief Justice Roberts held that the extraordinary capabilities of a modern cell phone require a different rule than the old "empty your pockets."

Chief Justice Roberts' opinion provides strong evidence that the Supreme Court will recognize that individuals have a reasonable expectation of privacy in the digital data that they store in the "cloud." The United States Department of Justice has consistently taken the position that a person does not have a reasonable expectation of privacy in information that is shared with or stored by a remote service provider, such as cloud storage of documents, photos or e-mails. The lower courts have split on whether law-enforcement officials need to obtain a warrant to search digital data in the cloud. Some courts have held that law enforcement is empowered, under the Stored Communications Act, to search stored digital data on a mere bureaucratic order.

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The Riley opinion bases its warrant requirement upon a finding that much of the information obtained from a cell phone actually is stored in the cloud. "Cloud computing is the capacity of Internet-connected devices to display data stored on remote servers rather than on the device itself. Cell-phone users often may not know whether particular information is stored on the device or in the cloud, and it generally makes little difference." Chief Justice Roberts derided the government's suggestion that law-enforcement agencies "develop protocols to address" concerns raised by cloud computing" short of requiring a warrant:

"Probably a good idea, but the Founders did not fight a revolution to gain the right to government agency protocols."

It is hard to imagine any court reading this statement and then allowing law enforcement to seize personal data from the cloud on a mere administrative subpoena.

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This decision is so powerful because it acknowledges that "Privacy comes at a cost." Cell phones have become important tools of the trade for criminal organizations and "can provide valuable incriminating information about dangerous criminals." But the warrant requirement is "an important working part of our machinery of government" and not merely "an inconvenience to be somehow weighed against claims of police efficiency."

Under Riley, cell-phone searches may be obtained with a warrant, or under emergency circumstances that justify immediate action. For example, the court wrote that police retained the flexibility to act without a warrant where a suspect is "texting an accomplice who, it is feared, is preparing to detonate a bomb, or a child abductor who may have information about the child's location on his cell phone."

There will be many decisions on the meaning of the Fourth Amendment in a digital age. I expect that Riley v. California will be the bedrock of the privacy rights of future generations.

Commentary by Mitchell Epner, an attorney specializing in white-collar crime, sports and entertainment law and intellectual property. He's also a former Assistant United States Attorney in the District of New Jersey. Follow him on Twitter @mitchellepner.