Opinion of the Court
to arrest doctrine applies to modern cell phones, which are now such a pervasive and insistent part of daily life that the proverbial visitor from Mars might conclude they were an important feature of human anatomy. A smart phone of the sort taken from Riley was unheard of ten years ago; a significant majority of American adults now own such phones. See A. Smith, Pew Research Center, Smartphone Ownership — 2013 Update (June 5, 2013). Even less sophisticated phones like Wurie's, which have already faded in popularity since Wurie was arrested in 2007, have been around for less than 15 years. Both phones are based on technology nearly inconceivable just a few decades ago, when Chimel and Robinson were decided.
Absent more precise guidance from the founding era, we generally determine whether to exempt a given type of search from the warrant requirement "by assessing, on the one hand, the degree to which it intrudes upon an individual's privacy and, on the other, the degree to which it is needed for the promotion of legitimate governmental interests." Wyoming v. Houghton, 526 U. S. 295, 300 (1999). Such a balancing of interests supported the search incident to arrest exception in Robinson, and a mechanical application of Robinson might well support the warrantless searches at issue here.
But while 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
