There are two types of Reverse Search Warrants: Geofence and Keyword Searches 

Geofence

Geofence warrants are a type of reverse warrant where the government seeks to know who was within a “geofence,” a defined physical area during a specific period of time. These are a type of “reverse warrant,” used to identify suspects when none are known without the data gathered by the warrant. The government utilizes geofence warrants to compel companies, such as Google, to produce information about devices interacting with their technology within a particular geographic region, which often includes many people who are wholly unconnected to the event being investigated. 

Key Resources

• Geofence Primer
  Outlines how geofence warrants are constructed and outlines strategies to challenge them in criminal cases

• Model Motion to Suppress
  Redacted motion arguing geofence warrants are overbroad and violate 4th Amendment protections

• When Google Searches for You
  Webinar discussing strategies defense lawyers can use to challenge geofence search warrants 

Cases

• United States v. Chatrie (Eastern District of Virginia) (Ongoing)
  Challenging the constitutionality of a warrant the collects the location information of hundreds of people who were near the scene of a crime

• People v Dawes (San Francisco, CA) (2022)
  Challenging the constitutionality of a warrant the collects the location information of hundreds of people who were near the scene of a crime

More on Geofence Warrants

Keyword Warrants 

These function in a similar way to Geofence warrants but look at search history as opposed to geographic location. Keyword warrants pulls data on everyone who searched a specific set of keywords and, using that date, works backwards to investigative leads or suspects. Like other reverse search warrants, these do not target someone suspected of being connected to a crime and many unrelated people's information is caught up in these searches.

Key Resources

• Seymour Rule 21 Petition
  Request for the Colorado Supreme Court to hear argument on a reverse keyword warrant after the district court's ruling

• Seymour Motion to Suppress
  Motion to Suppress from Colorado v. Seymour arguing reverse keyword warrants constitute an unconstitutional search

Cases

• People v Seymour (Denver, CO) (Ongoing)
  Challenging the constitutionality of a keyword warrant the collects the account information and search history of hundreds of people who made a Google search related to a physical address