The Supreme Court’s recent unanimous decision in Riley v. California barring warrantless searches of cellphones incident to arrest has rightly received a good deal of attention as an important example of the court’s adapting Fourth Amendment principles to the realities of modern technology.1 Chief Justice John Roberts’ opinion for the court astutely recognizes how technological innovations have shifted the analytical paradigm, memorably expressed in the comment that government arguments analogizing cellphones to wallets and similar items carried on the person were “like saying a ride on horseback is materially indistinguishable from a flight to the moon.”2
Just a week before the Supreme Court’s decision, the U.S. Court of Appeals for the Second Circuit issued an opinion that, while less far-reaching than Riley, illustrates similar struggles of the legal system to apply Fourth Amendment concepts to electronic data different in kind and exponentially larger in volume than evidence typically seized by law enforcement officers in years past. In United States v. Ganias, the Second Circuit reversed a tax evasion conviction, finding that the government violated the defendant’s Fourth Amendment rights by its unauthorized two-and-one-half year retention of the defendant’s personal files located on an imaged hard drive seized in an earlier investigation.3
