Little-Known Device Raises Big Fourth Amendment Implications

"Stingray" tracks all the mobile devices on a given network in an area

On Friday, EFF and the ACLU submitted an amicus brief in United States v. Rigmaiden, a closely-followed case that has enormous consequences for individuals' Fourth Amendment rights in their home and on their cell phone. As the Wall Street Journal explained today, the technology at the heart of the case invades the privacy of countless innocent people that have never even been suspected of a crime.

Rigmaiden centers around a secretive device that federal law enforcement and local police have been using with increased frequency: an International Mobile Subscriber Identity locator, or "IMSI catcher." These devices allows the government to electronically search large areas for a particular cell phone's signal—sucking down data on potentially thousands of innocent people along the way—while attempting to avoid many of the traditional limitations set forth in the Constitution.