Constitutionality of geofencing warrants goes before the Minnesota Supreme Court

Smartphones are immensely powerful tools. So powerful, in fact, that the device you’re holding in your hand delivers more computing capacity than the supercomputers the Department of Defense used for nuclear weapons research in the '80s—or the NASA guidance computer used to put Neil Armstrong on the moon in 1969.

While these mobile devices give us instant access to convenient tools and rich information, they also collect vast amounts of data about every aspect of our lives.

Without appropriate law enforcement restrictions and oversight, however, our constitutional right to protection from unreasonable searches and seizures is under threat.

Courts split on constitutionality of geofence warrants

Leveraging GPS or RFID technology, organizations can map geographic areas and deliver targeted content to mobile devices located within their prescribed boundary: A special offer to conference or sporting event attendees, for example.

Today, law enforcement taps this very same technology. Through the use of geofence warrants, sometimes referred to as reverse search warrants, they demand tech companies search their data warehouses and identify active devices present at crime scenes.

Are these searches constitutional? The courts are currently split.

In the United States v. Chatrie, the Fourth Circuit Court ruled that these law enforcement activities don’t represent a search, as mobile device users voluntarily share their locations with Google. As such, they can’t claim an expectation of data privacy.

The Fifth Circuit disagreed. In the United States v. Jamarr Smith, the Court found people rarely actively volunteer this data to Google. It found geofence warrants to be a violation of the Fourth Amendment and, therefore, unconstitutional.

Conviction attained through overly broad geofence warrant

Here in Minnesota, the Court of Appeals upheld one of these contested geofence warrants.

In 2021, the Dakota County Sheriff’s Office obtained a geofence warrant as part of a murder investigation; it demanded location data from Google for anyone who traveled within the prescribed geofenced area for a period of 30 days. This timeframe was so broad, that no court in the country had upheld a similar warrant before. What’s more, the warrant enabled law enforcement to request the identities of the mobile device users, as well as six months of their IP histories.

None of these mobile device users were ever informed that law enforcement had access to their location data, nor were the millions of people whose data were part of the initial search. (At this time, we still don’t know if the Dakota County Sheriff’s Office retained the data for future investigations or if it was destroyed.)

This data was foundational to the State of Minnesota’s case against Ivan Contreras-Sanchez; he was convicted of homicide in 2021.

Appealing the case to the Minnesota Supreme Court

On behalf of the Minnesota Association of Criminal Defense Lawyers, the Electronic Frontier Foundation, and the National Association of Criminal Defense Lawyers, I coauthored the amicus brief in the case of State of Minnesota v. Contreras-Sanchez. It argues that this overly broad warrant permits a sweeping intrusion into our private data without sufficient checks on law enforcement’s power, therefore representing an unconstitutional search.

Argued orally this fall, we have asked the Minnesota Supreme Court to overturn the trial court ruling and suppress all evidence that resulted from the warrant.