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The Supreme Court struck a huge blow on Monday in favor of privacy in the digital age. When the police want private information from your smartphone, we now know that’s a search within the meaning of the Fourth Amendment. And, to conduct that search, the police are going to need to prove probable cause that a crime occurred and that you were involved in it. And, they’re going to need a reasonably specific warrant describing what’s going to be searched. And, a judge is going to have to approve every step in that search process.

You may think that all seems straightforward and reasonable enough. You may even be surprised that the law didn’t already give you those protections. But the case was a close one with only five justices full-throatedly vindicating the Fourth Amendment’s privacy protection goals.

The case came to the Supreme Court from a bank robbery that happened in Richmond, Virginia, in 2019. Police didn’t know who did it so they got what’s become known as a geofence warrant. The short version of what that means is that they got a warrant to force Google to tell the police, using Google’s Location History technology, who was in the vicinity of the bank when it got robbed. Google complied, and police used that information to identify a man named Okello Chatrie as a suspect in the case.

But this isn’t a case about cops and robbers. It’s a case about how cops use peoples’ private digital data to catch robbers. More than that, it’s a case about how private the data on your phone really is and when that privacy interest has to give way to the government’s law enforcement efforts.

I covered the Chatrie case for Slate back in........

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