Geofencing Case Shows Surveillance Tech Should Be Closely Tracked

Should your phone’s proximity to a crime scene allow police to access your location? That is the question the US Supreme Court will consider in the case of United States v. Chatrie this week.

A technological technique dubbed “geofencing” uses Google’s location-tracking capacity to discover phone numbers near a crime to try to identify a perpetrator.

Police have relied on geofencing in thousands of cases over the last several years, including the Chatrie case, which involved investigation of an armed bank robbery in Midlothian, Va., in 2019.

The case gives the Supreme Court a golden opportunity to flesh out the constitutional limitations on police surveillance. It also exposes the urgent need for federal and state lawmakers to take action on police use of surveillance technology.

Series of Demands

Lacking reliable camera footage or other leads, the police in Chatrie tracked down the culprit through three separate court orders.

The first order (stage one) asked Google to provide data about all phones near the scene of the bank robbery for a one-hour period surrounding the crime; a subsequent request (stage two) for two hours’ worth of location data on some of the phones allowed the police to narrow the group to three anonymized numbers. Google confirmed one of the phones belonged to Okello Chatrie (stage three), who was later convicted.

The Supreme Court must decide whether this series of demands on Google was a “search” under the Fourth Amendment, a question that precedent has established depends on whether the police engaged in actions that infringed Chatrie’s “reasonable expectations of privacy.” If an action is a Fourth Amendment search, it often requires a warrant based on probable cause that the person, place, or thing searched will produce evidence of crime.

The police in Chatrie clearly didn’t have probable cause with respect to a particular person with either the first or second order, and perhaps not even the third. So if the police engaged in a Fourth Amendment search at those stages, and if probable cause with respect to a specific person is required, the police acted unconstitutionally.

To avoid that result, the Supreme Court could conclude that the police action wasn’t a “search,” which would mean the Fourth Amendment’s requirements didn’t apply. The initial decision in the US Court of Appeals for the Fourth Circuit so held, on two grounds.First, only a couple of hours of location information about any particular phone was discovered, so there was minimal invasion of privacy. Second, because Chatrie chose to turn on Google’s location tracking system, the Fourth Circuit determined he “voluntarily” surrendered his privacy.

The problem with holding that no search occurred in Chatrie is that it leaves geofencing completely unregulated by the Constitution; without bothering with a court order or any other justification, police would be able to scoop up all sorts of location information as a constitutional matter.

Further, as the Fifth Circuit held in a similar case, and as the Supreme Court itself intimated in Carpenter v. United States, location tracking is so central to modern living that a choice to use it is “voluntary” only in the most tenuous sense.

The Supreme Court could instead uphold the police action by conceding that the police in Chatrie engaged in a search but conclude that it was justified because police had probable cause for a particular place rather than for a particular person—the place where the bank robbery occurred and its environs.

That rationale is problematic because it at most allows a stage one inquiry that obtains all the phone numbers associated with the bank at the time it was robbed. It doesn’t allow police to whittle down the investigation to specific people within the geofence, as the police in Chatrie did in stages two and three. Geofencing would be useless to law enforcement.

The best approach to geofencing would be to consider all three stages a search—after all, they all obtain location information that most people using their phones consider private—but to require justification short of probable cause at each stage.

Consistent with the Fourth Amendment’s requirement that warrants describe with “particularity” the place to be searched, a stage one court order should narrowly circumscribe the geofence, perhaps even more so than occurred in Chatrie. Arguably, the police should have been satisfied with information about phones in the bank within 10 or 15 minutes of the time the robbery occurred.

Once the relevant group of phones has been determined, a cause requirement should govern stages two and three. However, contrary to the dissent’s view in the Fourth Circuit’s Chatrie decision, probable cause shouldn’t be required. Only plausible reasons for whittling down the number of phones in stage two, and for identifying who belongs to a given number in stage three, need to be provided to the judge.

As the majority opinion in the Fourth Circuit intimated in its initial Chatrie opinion, the small amount of information discovered at these stages—a person’s location during a two-hour period—doesn’t remotely approach what police find in a physical search of a person, house, or effect (such as boats or luggage), the types of searches that exercised the drafters of the Fourth Amendment. Something less than probable cause should be sufficient in such cases.

The Supreme Court has already adopted this type of reasoning in other Fourth Amendment cases. For instance, in cases like Terry v. Ohio, it has upheld the reasonableness of brief seizures and limited frisks on less than probable cause if there is some articulable suspicion about the person. And in previous tracking cases, it has signaled that minimally intrusive actions should be treated differently from “long-term” surveillance.

The advantages of this approach are twofold. For the police, it ensures technologies such as geofencing that can markedly enhance law enforcement will still be available to the police. For civil libertarians, it ensures these technologies will be subject to constitutional regulation.

Role of Legislation

Whatever the Court decides, it is high time legislatures got into the regulatory act. The three-stage process involved in Chatrie is Google’s invention. Revised as suggested, it may be the best way to proceed. But even if that is so, we shouldnt be depending on private entities to make the first move in policing the police.

Congress and state legislatures need to decide now when location tracking, facial recognition, license plate readers, CCTV, and other vehicles of mass surveillance can collect information, how long that information can be retained and kept secure, and when it may be accessed consistently with the Fourth Amendment.

This article does not necessarily reflect the opinion of Bloomberg Industry Group, Inc., the publisher of Bloomberg Law, Bloomberg Tax, and Bloomberg Government, or its owners.

Author Information

Christopher Slobogin is the Milton Underwood Chair at Vanderbilt University Law School.

Write for Us: Author Guidelines