For those who don't yet know, a stingray is a device that allows law enforcement to mimic a cell tower, and when a suspect's phone connects to it, to track his position, and sometimes even intercept his phone calls and text messages.
The ACLU is worried about police departments across the country using them and concealing this use from the public.
"This technology raises serious questions under the Fourth Amendment. The public is entitled to full disclosure of records so it can engage in an informed debate about the legality and wisdom of these devices, and provide oversight of their use," noted ACLU's Speech, Privacy, and Technology Project staff attorney Nathan Wessler.
It's difficult to know how a stingray functions, as its manufacturer - Florida-based Harris Corporation - has been secretive about its functionalities. Also, law enforcement agencies at all levels have been unwilling to share any details, likely because they signed a nondisclosure agreement with Harris Corp. that prevents them from confirming whether they use their devices.
The ACLU is worried about the information these devices gather about innocent people, how police departments protect the collected information, or even from whom they get the permission to use stingrays.
A few weeks ago, the ACLU has made a public records request to some 30 Florida police and sheriff's departments regarding their use of stingrays. Among these was the police department of the city of Sunrise, Florida, which refused to confirm or deny whether they use the devices.
"In this case, the response is not only a violation of Florida law, but is also fatally undermined by records the Sunrise Police Department has already posted online," says Wessler, as the Sunrise Police Department has already publicly acknowledged that it owns at least one Stingray by posting a document regarding a potential purchase of a a $65,000 upgrade to its existing device on its official website.
"An agency cannot acknowledge a fact in one context, but then refuse to confirm or deny the same information in response to a public records request," he pointed out. "Sunrise’s response might be laughable if it weren’t such a bald violation of government transparency laws."
The Sunrise Police Department is not the only local law enforcement force to use stingrays. "We have evidence that the police are using them in Arizona, California and Florida. We wanted to dig deeper in Florida as a case study of what is happening elsewhere," Wessler explained to the BBC.
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