The Supreme Court’s ruling this summer in Chatrie v. United States is the Court’s most impactful Fourth Amendment decision since Carpenter v. United States, where the Court held that law enforcement must have a search warrant to obtain cell-site location data from service providers. Chatrie extended the reasoning in Carpenter to require warrants for Google’s “Location History” data, which effectively allows law enforcement to locate and track a person’s movements.
The broad language in Chatrie made it inevitable that lower courts would consider whether to extend the decision beyond Google location data. To date, at least two courts have done exactly that. A federal court in Mississippi has applied the reasoning in Chatrie to “tower dumps,” which collect information associated with every cellphone connecting to particular cellular towers. And last week, the Fourth Circuit held that police conduct a Fourth Amendment search when they use a cell-site simulator—often called a Stingray—to force a suspect’s cellphone to reveal its location.
In re Four Applications for Search Warrants
In In re Four Applications for Search Warrants Seeking Information Associated With Particular Cellular Towers, federal investigators in Mississippi sought records associated with devices that connected to towers near several suspected gang-related crimes. The original applications covered nine locations and multiple providers. Investigators planned to compare the data and identify devices appearing at multiple crime scenes.
Unlike a traditional warrant, however, investigators did not begin with a particular person or phone. They wanted the cellular records of everyone who happened to be within the relevant areas, most of whom concededly had nothing to do with the crimes.
In August, U.S. District Judge Carlton Reeves upheld a magistrate judge’s refusal to issue the warrants and went further: he concluded that tower-dump warrants operate as unconstitutional general warrants. Even narrower applications—which reduced the locations and time periods and attempted to identify only devices appearing near multiple scenes—did not solve the problem because providers still had to search the larger universe of innocent users’ records first. As the court put the problem, post-search narrowing does not necessarily cure an un-particularized search.
The government filed a notice of appeal on September 3, placing the issue before the Fifth Circuit. That appeal could become an important test of what Chatrie actually means. Chatrie held that acquisition of highly precise location information is a search. The tower-dump litigation asks the next question: can probable cause and particularity exist when the investigative technique necessarily requires examining location information associated with potentially thousands of innocent people to determine who should become a suspect?
Andrews v. Baltimore City Police Department
The Fourth Circuit confronted the other side of the same technological problem in Andrews v. Baltimore City Police Department.
Baltimore police were searching for Kerron Andrews in connection with a shooting. Provider records narrowed his cellphone’s location to several city blocks. Police then used a “Hailstorm cell-site simulator” to pinpoint the phone inside a particular townhome.
A cell-site simulator essentially impersonates a cellular tower. Nearby phones connect to the device and transmit identifying signals. Officers can then move through an area while measuring the target phone’s signal strength until they locate it—without needing the cellular provider to supply the location. The technology can provide substantially more precise, real-time location information than ordinary cell-site records.
The facts became more unusual from there. Baltimore had obtained the technology from the FBI under a nondisclosure agreement requiring the police department to notify the FBI before disclosing its use in court. The agreement even contemplated prosecutors seeking dismissal of a criminal case rather than revealing details about the technology.
Andrews did not learn that police had used the simulator until roughly a year into his prosecution. Maryland courts ultimately found the warrantless use unconstitutional, the charges were dismissed, and Andrews—who had spent nearly two years in pretrial detention—later brought a civil action.
The Fourth Circuit has now expressly held that using the simulator constituted a Fourth Amendment search. Although the officers received qualified immunity in the civil case, the constitutional holding has obvious consequences in criminal cases.
Implications
Admittedly, the technologies across these three cases operate differently.
A geofence asks a technology company: Who was here?
A tower dump asks cellular providers: Which phones connected to these towers?
A Stingray asks a particular phone: Where are you right now?
The constitutional issues arising from their use is related, however, as technology now allows law enforcement to obtain information about physical location at a scale, speed, and precision that traditional surveillance could not achieve.
For defense lawyers, the practical lesson is that discovery into how police found the defendant is becoming as important as discovery into what police found afterward. An arrest report may simply say investigators “located” the suspect or developed his identity through “investigative means.” That description can conceal geofence data, tower records, cell-site simulators, automated license-plate databases, data brokers, flock cameras, or some combination of them. Counsel should therefore identify the entire chain of location information: what technology was used, what records were obtained, what legal process authorized the acquisition, how many uninvolved persons were swept into the search, and whether investigators narrowed the information before or only after accessing it.
Prosecutors, for their part, will need to be able to distinguish different kinds of technology from the expansive technology at issue in Chatrie. Additionally, prosecutors will likely need to address whether the good faith exception in Leon applies, as they did following Carpenter.