The Supreme Court handed down its decision in Carpenter v United States on June 22, 2018, holding that law enforcement does not have warrantless access to cell phone location data (also referred to as cell site location information or CSLI). This holding may translate into a new trial for Mr. Carpenter, who received a 100-year sentence for masterminding a string of robberies of Radio Shacks and (ironically enough, as noted by Justice Roberts) T-Mobile stores in Detroit. I was under the impression from watching Breaking Bad that criminal masterminds used burner phones. Maybe they didn’t do that back in 2011 when all of this happened.
The opinion talks at length about our expectations of privacy in the devices we carry and in particular how our CSLI is automatically shared with our cell phone service provider. It was that sharing that the Sixth Circuit had relied on when it held that because Mr. Carpenter had willingly disclosed his location to his service provider, he was no longer entitled to Fourth Amendment protection. SCOTUS disagreed and concluded that CSLI is unique and that even if we share it with a third party, the public doesn’t expect that third party to be the cops.
SCOTUS relied on how easy it is to establish a person’s movements with CSLI. However, it’s not necessarily as accurate as you might think (the National Association of Criminal Defense Lawyers has a nice primer on CSLI). In this case, the location data itself was presented at trial to establish Mr. Carpenter’s physical presence near the locations of the robberies at the times they were alleged to have occurred (as opposed to the police using the data to lead them to other evidence).
In another famous case, the murder conviction of Adnan Syed (chronicled by the first season of the Serial Podcast), CSLI evidence was used similarly at trial. Serial did a nice job explaining that CSLI is not the same as a GPS beacon attached to your belt. Rather, the data usually shows only which cell phone towers are “pinged” by your phone at various times. The point is that the evidence can show you were close to a particular cell tower, but it doesn’t show your exact location. Much like getting a “Welcome to Canada” message from your service provider when walking on the south side of Belle Isle, it’s just not that dispositive.