IN MAY a federal appeals court said police do not need a warrant to look at cellphone records that reveal everywhere you've been. Two days later, another appeals court said the National Security Agency (NSA) broke the law by indiscriminately collecting telephone records that show whom you call, when you call them, and how long you talk.
That looks like one victory for government snooping and one defeat. But both decisions highlight the precariousness of privacy in an age when we routinely store huge amounts of sensitive information outside our homes.
The Fourth Amendment prohibits "unreasonable searches and seizures" of our "persons, houses, papers, and effects." But the Supreme Court says it does not protect our papers once we entrust them to someone else.
In a 1976 case involving bank records, the Court declared that "the Fourth Amendment does not prohibit the obtaining of information revealed to a third party and conveyed by him to Government authorities, even if the information is revealed on the assumption that it will be used only for a limited purpose and the confidence placed in the third party will not be betrayed." Three years later, in a case involving phone records, the Court reiterated that "a person has no legitimate expectation of privacy in information he voluntarily turns over to third parties."
This dubious "third-party doctrine," enunciated before the Internet existed and mobile phones became ubiquitous, was crucial to the outcome of a case decided by the U.S. Court of Appeals for the 11th Circuit in May. The court said an armed robber named Quartavius Davis had no constitutional grounds to object when the FBI linked him to crime scenes with cellphone location data that it obtained without a warrant.
The court's logic was straightforward: Those records did not belong to Davis; they belonged to MetroPCS, his mobile phone company. So even though they revealed everywhere he went over the course of 67 days, he had no reasonable expectation that the information would remain private.
Dissenting Judge Beverly Martin noted that the majority's reasoning invites even bigger intrusions. "Under a plain reading of the majority's rule," she said, "by allowing a...