Today, along with the ACLU, EFF filed an amicus brief in the Sixth Circuit court of appeals in United States v. Sturdivant, a case where police warrantlessly tracked a suspect’s movements using Automated License Plate Reader (ALPR) data. Our brief details the vast, interconnected network of ALPRs that constantly track drivers around the country and argues that this tracking is a “search” under the meaning of the Fourth Amendment.

Sturdivant involves a series of robberies in and around Cleveland, Ohio. Using surveillance camera footage, police identified the make, model, and color of the robber’s car, but they did not know its license plate number. After running an open-ended search of two ALPR databases, Flock and ELSAG, officers learned a car belonging to the defendant had been tracked near sites of the robberies, eventually leading to his arrest. Faced with a motion to suppress the ALPR evidence, the district court held that Mr. Sturdivant had no reasonable expectation of privacy in his license plate number because it could be observed by members of the public, and that therefore he had no Fourth Amendment interest in not having his car tracked in public places.

But ALPRs are simply not comparable to observing an individual license plate on a passing car. As we’ve explained in many amicus briefs and in our lawsuits directly challenging ALPR use in San Jose, California and Wisconsin, ALPRs give law enforcement “a virtual time machine to view suspects’, or anyone else’s, past movements (and much more) with just the click of a button.” Just last month, a federal district court agreed and held that ALPRs are a “form of indiscriminate mass surveillance” that can violate the Fourth Amendment.

We hope the Sixth Circuit will reverse the lower court in this case and hold that ALPR searches require a warrant.