US v. Graham. In an en banc opinion, the Fourth Circuit overturned the panel’s decision in this case:

A majority of the panel held that, although the Government acted in good faith in doing so, it had violated Defendants’ Fourth Amendment rights when it obtained the CSLI without a warrant. . . . We now hold that the Government’s acquisition of historical CSLI from Defendants’ cell phone provider did not violate the Fourth Amendment.

The court concludes that the “third party doctrine” is controlling. This doctrine holds that a person cannot have any expectation of privacy in information transferred to a third party. So, in the case of cell site data: because the defendants necessarily shared their cell site information with their cell phone carriers, they could not legitimately expect privacy in that data.

The opinion analogizes the cell site information to pen register data – the numbers dialed when making a call – which the Supreme Court has previously held to fall within the third party doctrine. It also compares this information to IP addresses associated with emails. The Ninth Circuit has said those IP addresses are not protected by the Fourth Amendment.

Indeed, we expect that our banks, doctors, credit card companies, and countless other third parties will record and keep information about our relationships with them, and will do so for the entirety of those relationships — be it several weeks or many years. Third parties can even retain their records about us after our relationships with them end; it is their prerogative, and many business-related reasons exist for doing so. This is true even when, in the aggregate, these records reveal sensitive information similar to what could be revealed by direct surveillance. . . . Here, Defendants voluntarily disclosed all the CSLI at issue to Sprint/Nextel. And the very act of disclosure negated any reasonable expectation of privacy, regardless of how frequently that disclosure occurred or how long the third party maintained records of the disclosures.

Judge Wynn writes a strong dissent, which echoes many of the arguments set forth in the panel opinion. It begins on page 47:

A customer buys a cell phone. She turns it on and puts it in her pocket. With those acts, says the majority, she has “voluntarily conveyed” an unbounded set of personal location data to her service provider, all of which is unprotected by the Fourth Amendment. Here, that included 221 days’ worth of information, amounting to roughly 29,000 location-identifying data points for each Defendant.

Read the rest here.