Murder defendant challenges police use of ‘tower dump’

IN 2018, law enforcement officers were investigating five armed robberies and a sixth attempt in Dorchester, Mattapan, and Canton, one of which led to a fatal shooting. The police believed the same perpetrator, with a getaway driver, committed all the robberies, but they didn’t have a suspect. So they obtained search warrants for cell phone data from the towers closest to the robberies, on a suspicion that the same cell phone would have been in the vicinity of each robbery. 

Through these warrants, the police obtained information about 50,951 unique phone numbers. They used the data to identify Jerron Perry and Gregory Simmons as suspects. After obtaining additional warrants to search the men’s phones, homes, and cars, both were arrested.  

Perry, who was indicted for murder and other charges, is now challenging police use of data obtained from a so-called “tower dump.” His case, which will be heard by the Supreme Judicial Court on Wednesday, has the potential to regulate or even eliminate the police’s ability to obtain mass location data from cell phone towers.  

A number of privacy organizations have filed briefs in the case arguing that the concept of a “tower dump” is unconstitutional, and that investigators are casting too wide a net in gathering information. 

In Perry’s case, Suffolk Superior Court Judge Robert Ullmann found that Perry had standing to challenge the use of the cell phone data since a person “has a reasonable expectation of privacy in one’s cell phone location.” But he found that the police were justified in seeking a warrant on the grounds that most people carry around cell phones, and it is unlikely that someone not involved in the robberies would be in the vicinity of multiple crimes in different parts of Boston at the times the crimes were being committed.  

Ullmann wrote in his decision that “tower dumps” are legitimate police tools, since cell phone users tend to be aware that their phones are tracking their location, the information involved phone numbers but not names or identifiers, and, in this case, the warrants sought limited information that had a clear connection to the crimes. 

Attorneys for Perry are arguing that he never consented to the search, and the use of a “tower dump” warrant was too broad. 

“This Court has never approved of warrants that seek CSLI data of anyone in the vicinity of the crime when the Commonwealth lacked a suspect, phone number, and information that a phone was even used,” Perry’s attorneys wrote, using an acronym for cell site location information. “Warrants that broad implicate a host of privacy related issues and are plainly general warrants.” 

Perry’s attorneys say law enforcement took an unconstitutional approach of “obtaining a haystack in hopes of finding a needle.” They said obtaining the haystack “was an unconstitutional overreach that gravely threatens the privacy of every person.” 

Prosecutors say the ability to use tower dumps is important because it can provide the targeted information needed to solve a crime. 

Suffolk District Attorney Rachael Rollins wrote in a court brief that Perry has no expectation of privacy for the data in question, since it involved such a limited time frame. Attorneys for her office argue that the warrant was sufficiently narrow to capture data at specified dates and times that had a clear connection to crimes.  

Rollins’ spokesperson did not respond to a request for additional comment.  

Privacy advocates and organizations representing defense lawyers are asking the SJC to forbid the police from using “tower dump” requests – or at least institute safeguards governing when and how they can be used. The ACLU, the Committee for Public Counsel Services, the Massachusetts Association of Criminal Defense Lawyers, and the Electronic Frontier Foundation said a tower dump is gathering private data of tens of thousands of people to identify one suspect. The brief says a single phone company, T-Mobile, got 12,000 requests for tower dumps in 2020. 

“This electronic dragnet is a fundamentally new and invasive technology that evades longstanding practical barriers to sweeping police surveillance,” they wrote. “Even data from a single cell phone tower can reveal presence inside the home or a place of worship, at a protest or political rally, or coming and going from a hospital—not just for one individual, but for everyone with a phone who was present within the requested period of time.” 

“Tower dumps are…inherently unreasonable because they constitute bulk surveillance of many people without probable cause to believe that most of those affected have committed, or have evidence related to, a crime,” attorneys for the ACLU, the Committee for Public Counsel Services, and others wrote.   

The Surveillance Technology Oversight Project, a New York-based nonprofit that focuses on limiting technological surveillance in marginalized communities, said collecting large amounts of data is prone to errors, and to misidentifying suspects. “Cell tower dumps are a ticking time bomb—an error-prone, biased, and invasive tactic—that, if left unchecked, will fuel a wave of false arrests and convictions,” Kortz wrote in a brief.  

State and federal trial courts have ruled on the legality of individual warrants related to tower dumps, but no state supreme court has ruled on the constitutionality of the technique.