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.
What about the Robinson rule?
[W]hile Robinson’s categorical rule strikes the appropriate balance in the context of physical objects, neither of its rationales has much force with respect to digital content on cell phones. On the government interest side, Robinson concluded that the two risks identified in Chimel—harm to officers and destruction of evidence—are present in all custodial arrests. There are no comparable risks when the search is of digital data. In addition, Robinson regarded any privacy interests retained by an individual after arrest as significantly diminished by the fact of the arrest itself. Cell phones, however, place vast quantities of personal information literally in the hands of individuals. A search of the information on a cell phone bears little resemblance to the type of brief physical search considered in Robinson.We therefore decline to extend Robinson to searches of data on cell phones, and hold instead that officers must generally secure a warrant before conducting such a search.
The Court concludes that you can’t apply the physical search rule of Robinson to cell phones:
The United States asserts that a search of all data stored on a cell phone is “materially indistinguishable” from searches of these sorts of physical items. Brief for United States in No. 13–212, p. 26. That is like saying a ride on horseback is materially indistinguishable from a flight to the moon. Both are ways of getting from point A to point B, but little else justifies lumping them together. 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. A conclusion that inspecting the contents of an arrestee’s pockets works no substantial additional intrusion on privacy beyond the arrest itself may make sense as applied to physical items, but any extension of that reasoning to digital data has to rest on its own bottom.Cell phones differ in both a quantitative and a qualitative sense from other objects that might be kept on an arrestee’s person. The term “cell phone” is itself misleading shorthand; many of these devices are in fact minicomputers that also happen to have the capacity to be used as a telephone. They could just as easily be called cameras,video players, rolodexes, calendars, tape recorders, libraries, diaries, albums, televisions, maps, or newspapers.One of the most notable distinguishing features of modern cell phones is their immense storage capacity. Before cell phones, a search of a person was limited by physical realities and tended as a general matter to constitute only a narrow intrusion on privacy. See Kerr, Foreword: Accounting for Technological Change, 36 Harv. J. L. & Pub.Pol’y 403, 404–405 (2013). Most people cannot lug around every piece of mail they have received for the past several months, every picture they have taken, or every book or article they have read—nor would they have any reason to attempt to do so. And if they did, they would have to drag behind them a trunk of the sort held to require a search warrant in Chadwick, supra, rather than a container the size of the cigarette package in Robinson.But the possible intrusion on privacy is not physically limited in the same way when it comes to cell phones. The current top-selling smart phone has a standard capacity of 16 gigabytes (and is available with up to 64 gigabytes). Sixteen gigabytes translates to millions of pages of text, thousands of pictures, or hundreds of videos. See Kerr, supra, at 404; Brief for Center for Democracy & Technology et al. as Amici Curiae 7–8. Cell phones couple that capacity with the ability to store many different types of information: Even the most basic phones that sell for less than $20 might hold photographs, picture messages, text messages, Internet browsing history, a calendar, a thousand entry phone book, and so on. See id., at 30; United States v. Flores-Lopez, 670 F. 3d 803, 806 (CA7 2012). We expect that the gulf between physical practicability and digital capacity will only continue to widen in the future.The storage capacity of cell phones has several interrelated consequences for privacy. First, a cell phone collects in one place many distinct types of information—an address, a note, a prescription, a bank statement, a video—that reveal much more in combination than any isolated record. Second, a cell phone’s capacity allows even just one type of information to convey far more than previously possible. The sum of an individual’s private life can be reconstructed through a thousand photographs labeled with dates, locations, and descriptions; the same cannot be said of a photograph or two of loved ones tucked into a wallet. Third, the data on a phone can date back to the purchase of the phone, or even earlier. A person might carry in his pocket a slip of paper reminding him to call Mr. Jones; he would not carry a record of all his communications with Mr. Jones for the past several months, as would routinely be kept on a phone.
The realities of privacy are different in the “digital age”:
Prior to the digital age, people did not typically carry a cache of sensitive personal information with them as they went about their day. Now it is the person who is not carrying a cellphone, with all that it contains, who is the exception.According to one poll, nearly three-quarters of smartphone users report being within five feet of their phones most of the time, with 12% admitting that they even use their phones in the shower. See Harris Interactive, 2013 Mobile Consumer Habits Study (June 2013). A decade ago police officers searching an arrestee might have occasionally stumbled across a highly personal item such as a diary. See, e.g., United States v. Frankenberry, 387 F. 2d 337 (CA2 1967) (per curiam). But those discoveries were likely to be few and far between. Today, by contrast, it is no exaggeration to say that many of the more than 90% of American adults who own a cell phone keep on their person a digital record of nearly every aspect of their lives—from the mundane to the intimate. See Ontario v. Quon, 560 U. S. 746, 760 (2010). Allowing the police to scrutinize such records on a routine basis is quite different from allowing them to search a personal item or two in the occasional case.
The Court rejects the government’s argument that such searches should be permitted because a cell phone could be remotely wiped or encrypted. First, the Court says that this doesn’t seem to be a major problem. Second, the Court says that there are practical ways of minimizing the risk.