1 Just how much does the Constitution protect your digital data? 2 The Supreme Court will now consider whether police can search the contents of a mobile phone without a warrant if the phone is on or around a person during an arrest. 1 California has asked the justices to refrain from a sweeping ruling, particularly one that upsets the old assumptions that authorities may search through the possessions of suspects at the time of their arrest. 2 It is hard, the state argues, for judges to assess the implications of new and rapidly changing technologies. 1 The court would be recklessly modest if it followed California’s advice. 2 Enough of the implications are discernable, even obvious, so that the justices can and should provide updated guidelines to police, lawyers and defendants. 1 They should start by discarding California’s lame argument that exploring the contents of a smart phone—a vast storehouse of digital information—is similar to, say, rifling through a suspect’s purse. 2 The court has ruled that police don’t violate the Fourth Amendment when they go through the wallet or pocketbook of an arrestee without a warrant. 3 But exploring one’s smartphone is more like entering his or her home. 4 A smartphone may contain an arrestee’s reading history, financial history, medical history and comprehensive records of recent correspondence. 5 The development of “cloud computing,” meanwhile, has made that exploration so much the easier. 1 Americans should take steps to protect their digital privacy. 2 But keeping sensitive information on these devices is increasingly a requirement of normal life. 3 Citizens still have a right to expect private documents to remain private and protected by the Constitution’s prohibition on unreasonable searches. 1 As so often is the case, stating that principle doesn’t ease the challenge of line-drawing. 2 In many cases, it would not be overly onerous for authorities to obtain a warrant to search through phone contents. 3 They could still invalidate Fourth Amendment protections when facing severe, urgent circumstances, and they could take reasonable measures to ensure that phone data are not erased or altered while a warrant is pending. 4 The court, though, may want to allow room for police to cite situations where they are entitled to more freedom. 1 But the justices should not swallow California’s argument whole. 2 New, disruptive technology sometimes demands novel applications of the Constitution’s protections. 3 Orin Kerr, a law professor, compares the explosion and accessibility of digital information in the 21st century with the establishment of automobile use as a virtual necessity of life in the 20th: The justices had to specify novel rules for the new personal domain of the passenger car then; they must sort out how the Fourth Amendment applies to digital information now.