A Fifth Circuit Court of Appeals ruling this week will make it easier for police to track your movements through your cell phone after the court decided police aren't required to obtain a search warrant to track you.

The case involved a 2010 law enforcement request to obtain 60 days of cell phone location records from two cell phone companies. The government wanted to identify which cell phone towers a particular phone number had connected to in order to place a suspect at the scene of a crime, and submitted a request under the Stored Communication Act ("SCA") for access. The magistrate judge denied the request, understanding that records revealing your daily movements could show where you worship, what your medical conditions might be, and what political issues might interest you, not to mention who your friends and family are. It therefore rightfully ordered the government to apply for a search warrant supported by probable cause before accessing this sensitive data.

Naturally unhappy with the magistrate's conclusion, the government appealed first to the district court, which agreed with the magistrate, and then to the Fifth Circuit. Since there was no opposing party (the suspect wasn't informed of the surveillance and no criminal case was filed) we stepped in with the ACLU and other organizations, filing an amicus brief and participating at oral argument (WMA), urging the court to uphold the lower court opinions and rule a search warrant is needed in order to access cell tracking data since the data reveals extensive information about where a person goes and who they associate with.

In a misguided 2-1 decision, the Fifth Circuit reversed the privacy-protective lower court opinions and instead ruled the government did not need a search warrant to access historical cell site records. That's because the court focused not on what the data revealed -- a person's location over an extended period of time -- but rather on who owned and generated that data: the cell phone providers. Since these records were owned and created by the phone providers, the user has no expectation of privacy in them and thus no search warrant was needed to access that data. The court did not address whether people have a reasonable expectation of privacy in their movements and made clear its decision only concerned obtaining historical cell site records when a user makes or ends a phone call. In a compelling dissenting opinion, Judge Dennis noted that the constitutional issues were tricky ones and given the Supreme Court's reluctance to weigh in on the interplay between the Fourth Amendment and new technologies, the SCA should and could be interpreted to require a search warrant before police can access location data from a cell phone provider.

Throughout the majority opinion is the misguided belief that a user understands and voluntarily chooses to reveal their location to the cell phone provider and ultimately the government through the user's own free will. The court believed that your location is voluntarily turned over when the "user makes a choice to get a phone, to select a particular service provider, and to make a call." But common sense and experience calls this premise into question. Just last week the New Jersey Supreme Court ruled that police needed to get a warrant to track a person through their cell phone under under its state constitution. It noted a cell phone is "an indispensable part of modern life" and that "people buy cell phones to communicate with others, to use the Internet" but "no one buys a cell phone to share detailed information about their whereabouts with the police." While a cell phone user may naturally understand that they've given their location to the provider for a discrete and limited purpose -- to connect their phone call -- that is not the same as giving the government a detailed map of their movements. The New Jersey Supreme Court stated the "obvious" issue clearly: "cell phones are not meant to serve as tracking devices to locate their owners wherever they may be."

More generally the "third party doctrine" -- the idea you have no expectation of privacy in information turned over to third parties -- is dangerously eroding our Fourth Amendment protection at a time when cell phone companies and Internet service providers are stockpiling extensive personal information about all of us. Last year, Justice Sotomayor of the U.S. Supreme Court sounded the alarm in her concurring opinion in United States v. Jones writing the doctrine was "ill suited to the digital age, in which people reveal a great deal of information about themselves to third parties in the course of carrying out mundane tasks." But courts have been reluctant to follow Justice Sotomayor's cue in reexamining the doctrine. Its been up to state courts and legislatures to proactively protect people's location privacy while federal courts are reluctant to act, relying on the third party doctrine to reject a search warrant requirement for the data.

As more challenges to the constitutionality of cell site collection make their way through the federal courts, we hope judges will understand the only way to ensure our constitutional rights are protected is to find that the sensitive location information revealed by cell tracking deserves Fourth Amendment protection notwithstanding the fact the records are created and stored by cell phone providers.