Privacy in the age of cellphones

HOW easy should it be for the government to get its hands on data that reveals your location and movements sent from your mobile phone to service providers?

That’s the question at the heart of a case the US Supreme Court agreed on Monday to hear. The justices’ decision could redefine the limits on law enforcement access to cellphone-location records and the future of surveillance.

The petitioner in the case, Timothy Carpenter, was convicted in 2013 of a string of armed robberies in Michigan and Ohio, based partly on location data that placed his cellphone near the scene of several of the crimes. The police got that data under a federal law that requires only “reasonable grounds” to believe the information is “relevant and material” to an investigation. Carpenter challenged his conviction as an unreasonable search under the Fourth Amendment.

The lower courts ruled against him. There was no “search” in the first place, they said, because when he signed up with his phone company he agreed to let it record his location, and he couldn’t expect the information to remain private. That reasoning, known as the third-party doctrine, comes from a 1979 Supreme Court decision.

There’s good reason to question the scope of that doctrine now. In a 2012 Supreme Court ruling that the police needed a warrant to track a car with a GPS device, Justice Sonia Sotomayor said in a concurrence that the doctrine is “ill suited to the digital age”.

In Carpenter’s case, the government argues that location data is different from content, which is protected by the Fourth Amendment. But that distinction is increasingly meaningless.

The third-party doctrine needs to be reimagined in light of people’s new relationship to technology. If not, Congress should follow what several states have already done and pass legislation requiring warrants for phone-location data.