Last week the Supreme Court issued its ruling in Carpenter v. United States, with a five-member majority holding that the government’s collection of at least seven days-worth of cell site location information (CSLI) is a Fourth Amendment search. The American Civil Liberties Union’s Nathan Wessler and the rest of Carpenter’s team deserve congratulations; the ruling is a win for privacy advocates and reins in a widely used surveillance method. But while the ruling is welcome it remains narrow, leaving law enforcement with many tools that can be used to uncover intimate details about people’s private lives without a warrant, including persistent aerial surveillance, license plate readers, and facial recognition.
Timothy Carpenter and others were involved in a string of armed robberies of cell phone stores in Michigan and Ohio in 2010 and 2011. Police arrested four suspects in 2011. One of these suspects identified 15 accomplices and handed over some of their cell phone numbers to the Federal Bureau of Investigation. Carpenter was one of these accomplices.
Prosecutors sought Carpenter’s cell phone records pursuant to the Stored Communications Act. They did not need to demonstrate probable cause (the standard required for a search warrant). Rather, they merely had to demonstrate to judges that they had “specific and articulable facts showing that there are reasonable grounds to believe” that the data they sough were “relevant and material to an ongoing criminal investigation.”
Carpenter’s two wireless carriers, MetroPCS and Sprint, complied with the judges’ orders, producing 12,898 location points over 127 days. Using this information prosecutors were able to charge Carpenter with a number of federal offenses related to the armed robberies.