In a long-awaited decision, a federal court in Virginia ruled in United States v. Chatrie that a geofence warrant violated the Fourth Amendment, but that the fruits of the unconstitutional search could nevertheless be used against the defendant under the good faith exception to the warrant requirement. The Court found that the warrant at issue lacked particularized probable cause to search all nineteen Google users within the geofence. Because most geofence warrants inherently suffer from the same defect, the Chatrie decision calls into question law enforcement’s ability to pursue this form of search warrant in the future. However, the Court stopped short of finding that geofence warrants are categorically unconstitutional and declined to resolve several important questions at this thorny intersection of law and technology. This ruling leaves law enforcement, providers, and the public with continuing uncertainty about whether and under what circumstances geofence warrants pass constitutional muster, but suggests that they must be used more narrowly and with greater judicial oversight than they have been in recent years.
In Chatrie, law enforcement employed a geofiltered data search, more commonly referred to as a geofence search warrant, to identify a suspect in a bank robbery. Contrary to what the term suggests, the use of a geofence does not limit law enforcement’s search authority to a particular time and place. Instead, this process empowers law enforcement to demand that a provider comb through its records, dragnet-style, to determine which devices, and consequently which associated individuals, entered the designated geofence.
Like another geofence search warrant that was found to violate the Fourth Amendment, the warrant at issue in this case involved a three-step process:
- Create the virtual geofence zone to get a de-identified list of cell phones in the zone at the appointed times;
- Review the anonymized list to eliminate cell phones law enforcement deems irrelevant, and, without further court involvement, require Google to disclose additional location data (outside the zone specified in the warrant) for phones of interest during the specified time period; and
- Have Google identify the owners of selected cell phones law enforcement deems relevant.
The geofence zone in Chatrie was a circle 300 meters in diameter, covering a portion of Richmond, Virginia, that included a church, a parking lot, and the bank that had been robbed. The warrant covered a time frame of one hour, and it allowed law enforcement, in executing the warrant’s second step, to direct Google to provide further location data for an additional thirty minutes before and after that hour.
In executing Step 1 of the search, Google found nineteen mobile devices with Location History enabled had been within the geofence zone during the designated hour. Law enforcement then directed Google to provide additional data for all nineteen devices in Step 2, though it narrowed its request to just nine devices after getting pushback from Google. In Step 3, law enforcement required Google to provide identifying information for three individuals associated with devices of interest. The agent did not explain—to Google or to the court that issued the warrant—any basis for selecting nine devices in Step 2 or three of them in Step 3.
The information that Google provided under the warrant led police to identify Chatrie as a suspect and ultimately prosecute him in connection with the robbery. Chatrie then moved to suppress the evidence the search produced.
The U.S. District Court for the Eastern District of Virginia found that the warrant “plainly” violated the Fourth Amendment because law enforcement lacked probable cause to search each of the nineteen users whose devices were identified in Step 1 of the warrant execution process as having location history data responsive to the search parameters. The Court nevertheless denied suppression based on law enforcement’s good faith reliance on the warrant.
In its lengthy ruling, the Court considered some of the complex legal questions that geofence warrants raise. Though not addressed explicitly, the decision grapples with the question of whether a Fourth Amendment “search” occurs through the use of a geofence. No court has yet ruled on whether the use of such technology constitutes a search requiring a warrant under the Fourth Amendment. Like other courts that have evaluated the constitutionality of geofence warrants, the Court here assumed for the sake of argument—and because law enforcement applied for a warrant—that a search occurred. In sidestepping this issue, the Court avoided a fundamental underlying question: At what point in the geofence process does a search occur?
Chatrie argued that the search occurs when Google examines the location data of all mobile device users with Location History enabled in order to identify devices that were present in the geofence. The review of millions of users’ location data in Step 1 to identify the nineteen potentially relevant accounts was clearly something Google did only as a result of the warrant’s compulsion. If this initial review constituted a Fourth Amendment search, then law enforcement searched the data of millions of people—which would almost certainly fail to pass muster under the Fourth Amendment’s probable cause requirement.
But the Court did not address whether ordering that initial step was itself a Fourth Amendment search that required a showing of probable cause. Instead, the Chatrie opinion’s probable cause analysis focuses only on whether probable cause existed to subject the nineteen accounts identified in Step 1 to a further search in Step 2. Under this analytical framework, however, it is impossible to determine who, or even how many people, will be searched until Step 1 of the search execution is completed—which does not neatly square with the Fourth Amendment requirements that a warrant be sufficiently particular as to the persons to be searched and be predicated on probable cause as to each of them.
In addition to finding a lack of individualized probable cause for each of the nineteen devices located in Step 1 of the search, the Court found that Steps 2 and 3 impermissibly gave unbridled discretion to law enforcement to determine which of the nineteen devices to subject to further scrutiny. The Court held that such unchecked authority violated the Fourth Amendment’s particularity requirement. However, it explicitly left open the possibility that the problem could be addressed by requiring law enforcement to return to court for judicial approval of the selections made in each of Steps 2 and 3.
The Court did not rule on whether Chatrie had standing to challenge the warrant to Google for his data. If the search at issue is characterized as a search of Google’s property, then Chatrie would not have the right to challenge the search. If, however, the search is characterized as a search of Chatrie’s records, then he should have the right to challenge its validity. Whether criminal defendants have standing to challenge the use of geofence warrants could be important to the development of this area of law. If defendants do not have standing to challenge these warrants, then it will fall only to the providers who receive the warrants to decide whether to challenge their use, effectively depriving criminal defendants of the opportunity to exercise their Fourth Amendment rights. The Court urged legislatures to consider taking action in this area to protect citizens’ privacy.
Finally, as to the third-party doctrine, the Court considered whether Chatrie waived any expectation of privacy he might have had in his location data by sharing it with Google, but concluded that the third-party doctrine likely should not apply. The Court also doubted that an individual waives all privacy interests in his location data and assumes the risk that Google would share such data with law enforcement merely by opting in to a location service and suggested that the adequacy of the provider’s consumer-facing privacy disclosures plays some role in whether privacy interests have been waived. However, the Court stopped short of ruling on this issue.
This decision adds to what is now a handful of rulings addressing the constitutionality of geofiltered data search warrants under the Fourth Amendment. However, there are still significant open questions that courts have not addressed—either because these questions have not been squarely presented before courts in a manner requiring courts to rule on them or because courts have avoided the issues in deciding the cases before them. Some of those questions may be answered by state legislatures like New York’s, which is considering a bill to ban geofence warrants. But more likely the answers will come from federal and state courts addressing suppression motions and warrant applications arising from the explosive use of this still nascent investigative technique.