ACLU: Tracking Your Cellphone Location Should Require a Warrant

Should the government get a warrant before it obtains seven months' worth of your cellphone location data, which details practically everywhere you've been in that time?

The U.S. government argues it doesn't need to, and a district court judge agreed. But the American Civil Liberties Union disagrees, arguing that such sensitive information should be protected by the Fourth Amendment and thus require a warrant.

The ACLU filed a brief (.PDF) on Monday in a criminal case where the government obtained almost 30,000 cell site location data points for each of two defendants, Aaron Graham and Eric Jordan, who robbed a Burger King and a McDonald's on February 5, 2001, in Baltimore, MD.

The data shows which cellphone towers the defendants' phones were connecting to in every one of their calls during the 221 days tracked. The prosecutors obtained the data from Sprint with a simple court order — whose standard is less difficult to meet than a warrant.

For the ACLU, that kind of data is so detailed and revealing that it amounts to a search and should only be accessed when there is a probable cause. "That kind of information reveals a great deal of extremely private information about someone's life," Nathan Wessler, an ACLU staff attorney, told Mashable.

According to Wessler, it can reveal whether a person was at home or not at any point during a day, and whether he or she slept at home a certain night. This information could potentially reveal sensitive information such as, for instance, infidelities, or other kind of personal information, like visits to the doctor, or to an alcohol support group.

"Each time a cell phone makes or receives a call or text message, the wireless provider logs the cell towers the phone connected to during that communication," the ACLU wrote in a blog post. "Cellphone tracking therefore allows the government to reach back into the past and pull up a record of where we have been on any given day."

In fact, the ACLU analyzed the data obtained in the case and, for example, learned that Graham's wife was pregnant at the time, since 29 calls began or ended in the sector where her gynecologist was located.

The ACLU filed the brief along with the Electronic Frontier Foundation (EFF), the Center for Democracy and Technology, and the National Association of Criminal Defense Lawyers.

In the trial, the judge did not think a warrant to access the location data was required because of the so-called "third party doctrine," a legal theory which claims that a consumer who turns over data, such as phone numbers, to third parties, such as phone companies, has no expectation of privacy over those records. It's a similar argument, in a way, that allows the NSA to obtain large amounts of metadata from Verizon, AT&T and other telecoms without a warrant.

But Wessler thinks that, in this case, the doctrine shouldn't apply.

"When it comes to cellphone location information, no person has voluntarily turned that information over to their cellphone provider," he says. And, moreover, they might not even be aware their provider is logging their location.

"For the government to argue that you have no privacy interest in your movements throughout your neighborhood, your city, your home during the day, is really disconnected from the way that people understand their privacy rights," Wessler said.

The ACLU is comparing this case to the landmark 2011 U.S. v. Jones GPS tracking case, where the Supreme Court ruled that affixing a GPS tracking device to a suspect's car for a month constituted a "search" under the constitution.

Wessler also notes that cell tower location data can be very precise, especially in urban areas, where there's a higher concentration of cellphone towers. And the precision is only destined to go up, since more towers are being installed to keep up with more demand for cellphone data service. "The more dense those towers are, the more precise the location is,'" said Wessler.

For him, it's time courts set clear rules on when the government needs a warrant to get this information because "there's only one direction this technology is going, and that is toward more and more precise tracking of every American's location."

Image via iStockphoto, nouchka, Map screenshot courtesy of ACLU