In August, we blogged about a court decision from the federal court in the Eastern District of New York that held that law enforcement agents are constitutionally obligated to get a warrant based on probable cause before obtaining historical cell phone location information. And in September, we wrote about an opinion from the 3rd Circuit Court of Appeals holding that judges may order the government to get a warrant based on probable cause for historical cell phone location information. However, the 3rd Circuit also held that judges are not obligated to require probable cause, and cautioned that they should only require the government to meet this high standard on rare occasions. Now another court has joined the fray. In a detailed opinion (PDF) citing documents obtained through litigation by the ACLU and Electronic Frontier Foundation, Judge Stephen Smith of the Southern District of Texas held that “warrantless disclosure of cell site data violates the Fourth Amendment.”

A few aspects of the opinion (PDF) are worth noting:

The government’s application appears to request historical location information for whenever the phone was turned on, not just when calls were made. According to Judge Smith, “the Government seeks continuous location data to track the target phone over a two month period, whether the phone was in active use or not.” This is notable because the cell tracking applications we have seen previously only sought location information for those moments when an individual actually made a phone call. The government is now asking for a great deal more information, and consequently its requests are now more invasive than we previously thought.

According to Judge Smith, “the Government seeks continuous location data to track the target phone over a two month period, whether the phone was in active use or not.” This is notable because the cell tracking applications we have seen previously only sought location information for those moments when an individual actually made a phone call. The government is now asking for a great deal more information, and consequently its requests are now more invasive than we previously thought. Cell phone tracking information is increasingly accurate. The opinion devotes many pages to explaining the ways in which cell tracking information has grown more accurate over time. In fact, it is because of these “refinements in location-based technology” that Judge Smith concludes that requests for cell tracking information trigger the Fourth Amendment’s warrant requirement.

The opinion devotes many pages to explaining the ways in which cell tracking information has grown more accurate over time. In fact, it is because of these “refinements in location-based technology” that Judge Smith concludes that requests for cell tracking information trigger the Fourth Amendment’s warrant requirement. The Fourth Amendment requires the government to get a warrant and show probable cause to obtain historical cell tracking information. The court reached this conclusion both because cell tracking reveals information about constitutionally protected spaces such as the home, and because the prolonged nature of such surveillance is very invasive. The court likened the records sought by the government to “a continuous reality TV show, exposing two months’ worth of a person’s movements, activities, and associations in relentless detail.”

As we have explained elsewhere, the ACLU agrees with Judge Smith that the government should be required to obtain a warrant and show probable cause before obtaining cell tracking information. As powerful new technologies enhance the ability of government agents to track our every move, it becomes all the more important that the courts hold the government to a rigorous standard before the government can access such sensitive information.