Rex Hammond was a “person of interest” in a series of armed robberies. Rather than conduct ordinary police work to locate him, Detective Cory Ghiringhelli made an “exigency request” for AT&T to ping cell site location information (CSLI) from Hammond’s phone. Once granted, Ghiringhelli had access to Hammond’s precise location and to his movements in real-time. Ghiringhelli used this access to track Hammond and to obtain evidence later used to convict him. Hammond appealed his conviction, arguing that Ghiringhelli’s use of his cell phone data violated his Fourth Amendment freedom from unreasonable searches under Carpenter v. United States. In Carpenter, the Supreme Court held that collecting historicalCSLI without a warrant was an unconstitutional search.

But the Seventh Circuit disagreed. It held Ghiringhelli’s actions were not a search under the Fourth Amendment because he only tracked Hammond for a few hours. Because the CSLI was real-time data instead of historical data, Carpenter did not apply. Further, since Hammond happened to be traveling “on public, interstate highways and into parking lots within the public’s view” when Ghiringhelli decided to start tracking him, Hammond had no subjective expectation of privacy that society is prepared to recognize as ‘reasonable’ under Katz v. United States.

The Seventh Circuit’s analysis here not only missed the point, but it also managed to untether a Fourth Amendment case from the Fourth Amendment. Using doctrinal glosses to the exclusion of the constitutional text, the Seventh Circuit’s reasoning was based on distinctions without a difference and principles without actual grounding in the Fourth Amendment.

In our new brief, Cato and the Rutherford Institute ask the Supreme Court to take up Hammond’s case to establish that accessing real-time CSLI is a search under the plain meaning of the text of the Fourth Amendment. We also ask the Court to reaffirm that the ultimate test of whether government conduct constitutes a search is the terms of the Fourth Amendment itself. Although cell phone users do have a reasonable expectation of privacy in their devices today, no circuitous inquiry into societal expectations is necessary to conclude that harvesting data from Hammond’s phone to track him down was a Fourth Amendment search.

The Fourth Amendment provides that “[t]he right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated[.]” The three-part analysis we propose for this case, then, is hardly novel: we ask whether there was a search or seizure, whether this search or seizure was of “persons, houses, papers, [or] effects,” and whether the search or seizure was reasonable. When the government sets out to learn a person’s precise location and reveals such data, it conducts a search within the meaning of the Fourth Amendment. Here, pinging Hammond’s phone for nonpublic data with the purpose of locating him was a search of Hammond’s “person” and “effects.” To do so without a warrant based on probable cause was unreasonable.

An original purpose of the Fourth Amendment was to place obstacles in the way of a “too-permeating police surveillance.” But current doctrine allows police to effectively convert private cellphones into government tracking devices. The Court should return to the text of the Fourth Amendment when the need for novel applications arises. Reorienting Fourth Amendment doctrine towards the Fourth Amendment’s plain meaning is critical to ensure its original protections apply with equal force to new technology.