The ACLU-MN and the ACLU filed an amicus brief on Friday that urges the Minnesota Supreme Court to prevent law enforcement from using “geofence” searches. Geofence searches (also called "location warrants") are a type of reverse search, which allow law enforcement to look at the data of millions of people in order to find information they want about a few—a needle in a haystack. Geofence searches happen when law enforcement wants to learn who was present at the scene of a crime.
In this case, law enforcement provided Google with a time frame (about 30 days) and a location (about 290 feet by 65 feet along a public highway) and asked Google to sift through millions of records to find any phones that showed up. Google gave law enforcement data on 31 individuals who appeared within that geographical area during only five days, as Google told law enforcement that 30 days was unreasonable.
None of the 31 individuals were informed that law enforcement had access to their location data, neither were the millions of people whose data was initially searched for law enforcement. We do not know if the data was kept in police records for future use or destroyed.
Reverse searches like this one were unimaginable 30 years ago—the government shouldn’t be able to take advantage of technological advancements to invade our privacy.