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California Court Rejects Geofence Warrant

by Anthony W Accurso

A California trial court held that a geofencewarrant obtained by the San Francisco PD violated the Fourth Amendment and the recently enacted California Electronic Communications Privacy Act (“CalECPA”), requiring future warrants to be more narrowly tailored.

People v. Dawes, Court No. 19002022, SW# 42739, involved a 2018 burglary for which the police had difficulty identifying a suspect. Police obtained a warrant to obtain location data from Google’s Location History database, which enabled police to identify Laquan Dawes.

For those unfamiliar with the details of geofence warrants, these usually involve a three-step process. First, Google returns advertising IDs and location history for all the Google-tracked devices in an area during a specific window of time. In the second step, police narrow the list of devices but may expand the geographic area and time window to track the movements of the devices of interest. The third step involves narrowing the list of devices further, and Google then provides detailed user info on the remaining devices.

In this era of mass incarceration and the surveillance state, most courts simply approve tech-oriented warrants without understanding what they are authorizing police to do. However, a growing number of judges are pushing back against geofence warrants because they understand these warrants reveal private information on sometimes thousands of innocent people.

Police often go to Google because of the wealth of data the company collects on its users. As the U.S. District Court for the Eastern District of Virginia recently wrote, “Location History appears to be the most sweeping, granular, and comprehensive tool—to a significant degree—when it comes to collecting and storing location data.” United States v. Chatrie, No. 3:19cr130 (E.D. Va. 2022).

Yet experts have called the accuracy of Google’s location data into question, leaving many courts to suspect that this method regularly identifies false positives and fails to include actual perpetrators. Further, there is often no evidence that criminals were using a phone that contributes to Google’s database.

The court in Dawes found the warrant was unconstitutional for two reasons. First, the geographic area requested was too large. The court wrote, “[t]his deficiency in the warrant is critical because the geofence intruded upon a residential neighborhood and included, within the geofence” several homes, a church, a chain restaurant, a hotel, apartments, a senior living facility, a self-storage business, and two busy streets. All the people having mobile phones in that geographic location had their data seized but “were not suspected to have any involvement in the burglary, either as a suspect, victim, or witness.” Second, the court also ruled that allowing a three-step process to ensue from one warrant “[p]rovided officers with unbridled discretion to determine who to target for further investigation.”

The trial court in Dawes used a provision of CalECPA to suppress the location history evidence but stressed the narrowness of the ruling. San Francisco PD will have to narrow the scope of their geofence warrants going forward and will have to obtain a warrant for each stage of the process. But these warrants will continue to be issued and will allow police to pry into the private lives of innocent citizens until they are outlawed or Google quits spying on its users, neither of which seems likely in the near future.


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