This is a very important ruling that should serve as a good precedent for technologically-based privacy rights in the future.
The Supreme Court handed down a landmark opinion today in Carpenter v. United States, ruling 5-4 that the Fourth Amendment protects cell phone location information. In an opinion by Chief Justice Roberts, the Court recognized that location information, collected by cell providers like Sprint, AT&T, and Verizon, creates a “detailed chronicle of a person’s physical presence compiled every day, every moment over years.” As a result, police must now get a warrant before obtaining this data.
This is a major victory. Cell phones are essential to modern life, but the way that cell phones operate—by constantly connecting to cell towers to exchange data—makes it possible for cell providers to collect information on everywhere that each phone—and by extension, each phone’s owner—has been for years in the past. As the Court noted, not only does access to this kind of information allow the government to achieve “near perfect surveillance, as if it had attached an ankle monitor to the phone’s user,” but, because phone companies collect it for every device, the “police need not even know in advance whether they want to follow a particular individual, or when.”
Perhaps the most significant part of today’s ruling for the future is its explicit recognition that individuals can maintain an expectation of privacy in information that they provide to third parties. The Court termed that a “rare” case, but it’s clear that other invasive surveillance technologies, particularly those than can track individuals through physical space, are now ripe for challenge in light of Carpenter. Expect to see much more litigation on this subject from EFF and our friends.