Davis successfully argued that the public maintains a reasonable expectation of privacy that their public movements won’t be catalogued for the government unless a probable cause warrant is issued by a judge. The authorities did not get a warrant in Davis’ prosecution.
“Thus, the exposure of the cell site location information can convert what would otherwise be a private event into a public one. When one’s whereabouts are not public, then one may have a reasonable expectation of privacy in those whereabouts,” the court ruled. (Because the court decided to rehear the case, the decision is no longer case law.)
At least three other federal circuits, there are 13 altogether, have ruled differently from the 11th Circuit. In all of the cases, the authorities argued that so-called cell-site records are not constitutionally protected and are business records that telcos may hand over if the government asserts there are reasonable grounds to believe the data is relevant to an investigation.
The stakes are high. The government is embracing warrantless cell-site tracking as a surveillance tool in the aftermath of a Supreme Court ruling in 2012 that said the authorities needed a warrant to affix GPS trackers to vehicles. In that case, the justices ruled that the actual installation of a GPS device on a vehicle was the equivalent of a search usually requiring a warrant. Mobile phones, usually in a suspect’s pocket or purse, don’t require any government installation.
The American Civil Liberties Union and the Center for Democracy & Technology also weighed in to the case with a filing Friday. They said a massive amount of information was at stake:
As of December 2013, there were 335.65 million wireless subscriber accounts in the United States, responsible for 2.61 trillion annual minutes of calls and 1.91 trillion annual text messages. Cell phone use has become ubiquitous: more than 90 percent of American adults own cell phones and more than a third of US households have only wireless telephones.
The National Association of Criminal Defense lawyers also took the ACLU’s and CDT’s side, filing its own brief [PDF] Friday.