Exclusive: Judge Rules ‘Tower Dumps’ Unconstitutional

A federal judge in Mississippi ruled that a frequently-used law enforcement technique of pulling large swaths of data from cellular towers to find alleged criminal activity is unconstitutional – a move experts say could prevent investigators nationwide from using so-called “tower dumps” in future cases. 

On Friday, U.S. Magistrate Judge Andrew Harris of the Southern District of Mississippi rejected a bid by federal investigators to obtain sweeping search warrants that would have pulled data from four cellular providers and phone towers covering nine locations.

In a sealed federal affidavit, the FBI had requested the expansive search as part of an investigation into a string of killings, shooting and car thefts allegedly committed by a local gang over a 14-month period, the ruling said. 

Details about the case, including the locations of the alleged crimes, the underlying search warrants and its targets remained sealed because it is an ongoing FBI investigation. The Mississippi judge’s order has not previously been reported.

In his ruling, Harris said the proposed search would violate the Fourth Amendment, which protects people from unreasonable search and seizures by the government, because the sweep might include the data of thousands of people not suspected of a crime. 

“The Government is essentially asking the Court to allow it access to an entire haystack because it may contain a needle,” Harris wrote, adding that “the haystack here could involve the location data of thousands of cell phone users in various urban and suburban areas.”

“The Fourth Amendment does not permit law enforcement to rummage through troves of data and themselves determine the existence of probable cause to support the seizure of that data,” Harris said.

The order for the first time significantly extended the scope of an August ruling in a federal appeals court that found that the use of a geofence warrant — in which law enforcement sends a request to Google for the location data of phones at a specific location  — unconstitutional. That case, also in Mississippi, involved the robbery of a Postal Service worker. 

After investigators’ initial submission to the court, Judge Harris asked prosecutors to address the constitutionality of its request in light of that ruling, which was made by the U.S Court of Appeals for the 5th Circuit in the case United States v. Smith in August. According to the ruling, Harris was unmoved by DOJ’s subsequent filings.

Privacy experts who reviewed the opinion for Court Watch praised the ruling and stated it could have far-reaching effects on law enforcement’s use of tower dumps in the future. 

Jennifer Granick, an attorney with the Speech Privacy and Technology project at the ACLU, told Court Watch she was not familiar with another tower dump case “that holds that the technique is an unconstitutional general warrant in essentially every case.” Andrew Crocker of the Electronic Frontier Foundation (EFF) called the opinion “a really positive sign.”

Tower dumps are a collection of data on all devices, such as cell phones, that have connected to specific cellular towers during a set time block. Law enforcement has long relied on tower dumps to crack complex cases and track suspects via cell phone data. Last year, investigators with the Bureau of Alcohol, Tobacco, Firearms and Explosives successfully used a tower dump to identify a man accused of a string of gun store robberies in Pennsylvania.  More recently, investigators asked a federal judge for approval to perform a tower dump while investigating vandalism at a Federal Aviation Administration facility in Vermont. 

Editor’s note: This filing was marked in a docket titled, USA v. Unknown. It sat untouched for a number of days. Without our reporting, you likely would not have learned of the judge’s decision. If you’d like to support this type of reporting, please consider upgrading your subscription. 

Law enforcement sources stressed to Court Watch that tower dumps are typically used as a last resort when other investigative leads have been exhausted. At least one privacy expert who spoke with Court Watch strongly disputed that assertion. Federal judges in the past have chided law enforcement for using too large of a dragnet to collect data.

Friday’s ruling raises the question of whether the practice of using any tower dump would be legally acceptable even if narrowly tailored to limit the number of innocent peoples’ data that could be collected. 

Sen. Ron Wyden (D-Oregon) told Court Watch that “dragnet surveillance” tactics like tower dumps make “a mockery of the Fourth Amendment.”

“Cell tower dumps sweep up the personal data of tens of thousands of innocent Americans,” Wyden, a longtime advocate for privacy rights and limits on government surveillance tools, told Court Watch in an emailed statement. 

“But for too long, courts have rubberstamped surveillance dragnets by ignoring that innocent bystanders have privacy rights too. I am glad to see the federal courts start to say no to these modern-day ‘general warrants.’” 

An inquiry to Verizon was not returned. T-Mobile and AT&T both declined to comment. The Department of Justice did not respond to a request for comment.

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