But a court filing recently uncovered by the ACLU suggests another reason for the secrecy: the fact that stingrays can disrupt cellular service for any phone in their vicinity—not just targeted phones—as well as any other mobile devices that use the same cellular network for connectivity as the targeted phone.
Civil liberties groups have long asserted that stingrays are too invasive because they can sweep up data about every phone in their vicinity, not just targeted phones, and can interfere with their calls. Justice Department and local law enforcement agencies, however, have refused to confirm this or answer other questions about the tools.
But in the newly uncovered document (.pdf)—a warrant application requesting approval to use a stingray—FBI Special Agent Michael A. Scimeca disclosed the disruptive capability to a judge.
“Because of the way, the Mobile Equipment sometimes operates,” Scimeca wrote in his application, “its use has the potential to intermittently disrupt cellular service to a small fraction of Sprint’s wireless customers within its immediate vicinity. Any potential service disruption will be brief and minimized by reasonably limiting the scope and duration of the use of the Mobile Equipment.”
The document was previously sealed and only came to light after the defense attorney for a defendant in the case filed a motion last year to dismiss evidence collected by the stingray.