United States v. Chatrie is a noteworthy case in that it is the first involving geofence warrants to reach a federal court of appeals, and the ultimate decision could have a major impact on mobile device privacy. The American Civil Liberties Union has filed an amicus brief arguing that Google location data should be suppressed in cases involving these non-specific warrants due to a lack of probable cause and violation of Fourth Amendment protections.
ACLU: Dragnet for Google location data impacts people with no connection to crimes
Geofence warrants have been a contentious topic since the first emerged in 2016. Phones essentially act as a continual location tracker, and law enforcement agencies use these warrants to gather lists of individuals within the area of a crime and use them as investigative leads.
A warrant must be obtained to access Google location data in this way, but Google themselves have been the determinant of the conditions that warrant has to meet for them to agree to provide protected user data (and have not yet been challenged in court by government or law enforcement agencies). This has left a broad amount of room for magistrate judges across the country to determine whether they will or will not sign such a warrant, and there have been a variety of outcomes and opinions published. The United States v. Chatrie case, which involves a 2019 bank robbery in Virginia in which the suspect was eventually tracked down by a geofence warrant for phones within the area of the robbery during an hour-long window, is the first to go before an Article III federal judge whose ultimate ruling might create a firm precedent to be referred to in similar cases.
The legitimacy of geofence warrants presently hinges on them not really being considered a “search,” at least in Fourth Amendment terms, due to the legal view that information that is surrendered voluntarily is not subject to the same level of protection. However, “voluntary” is up for debate here, at least as concerns Google location data. A cellular phone is nearly mandatory to participate in everyday life at this point, and Google has already faced legal issues in numerous countries for not being entirely forthcoming about how it is tracking Android users and making the opt-out process straightforward. It is technically possible to stop Google from tracking location data, but some of its apps (such as Maps) require special steps that are not immediately apparent, it is not an opt-in system, and phone users that are not technically inclined cannot necessarily be said to be reasonably informed about how all of this works.
Even if geofence warrants are not found to be a protected form of search in Fourth Amendment terms, there remains the question of scope and appropriateness. The case in question saw 19 suspects listed that were within 150 meters of the bank that was robbed, within a half-hour on either side of the robbery. At least one party was found to be much too far from the bank to be either a witness or participant at the time the incident occurred, yet their identity was captured and they were investigated by law enforcement.
The ACLU’s argument is that geofence warrants are fundamentally defective in this way; they will inevitably sweep up people that are not related to the crime, and thus the warrants are self-evidently unreliable. The organization is also looking for clear limitations on what magistrate judges can authorize in geofence warrants, pointing out that the type of information that was turned over was entirely determined by Google and the investigating officers rather than having guidelines from the court.
Geofence warrants face first real threat in court
The use of Google location data applies beyond those just using Android phones, as Google also collects tracking data through various other apps when used on an iPhone or other devices. And as a recent settlement with 40 state attorneys general revealed, from 2014 to 2020 Google Maps was continuing to collect tracking data from all sorts of users even if tracking was disabled in the app.
Though the conditions can vary, Google location data tends to be quite accurate and precise as it makes use of the phone’s GPS coordinates. Outside the Maps tracking is usually accurate to within about 20 meters; it can become much more inaccurate when the subject enters a building, but Google also uses nearby WiFi networks and cell towers as a supplement for estimating location. In 2020 the company announced that it would start automatically deleting this data after 18 months, after it was revealed that its “Sensorvault” database was storing Google location data movement records from as far back as 10 years and that law enforcement was accessing this via geofence warrants.
Google location data is not always just handed over to the police; the company has a history of pushing back against overbroad warrants, and it has published a Transparency Report to help individuals understand how it handles these requests. However, it is difficult for the subjects of geofence warrants to know when they’ve been included and had data turned over, and Google and law enforcement largely hash out between themselves what ends up being shared with little management from courts. Google has also consistently refused to take a public position on whether or not geofence warrants should be legal.
The court decision may come down to a determination of whether investigators appropriately invoked the Fourth Amendment’s “good faith” exception, which allows for otherwise illegal searches if the police can demonstrate that they believed that they had legal authority in the situation. The ACLU’s argument, echoed by another amicus brief filed by the Electronic Frontier Foundation (EFF), points out that it is impossible to be acting in good faith if one is aware that innocent and unrelated people will be swept up in a broad dragnet by a geofence warrant.
