A local activist has filed a new lawsuit against the Chicago Police Department in an attempt to learn how the city uses fake cell tower devices, also known as stingrays.

Relatively little is known about the devices, which are used to track targeted phones and can also be used to intercept calls and text messages.

The American Civil Liberties Union recently began a campaign to learn more about how stingrays are used by filing public records requests in Florida, the home state of the Stingray’s manufacturer, Harris Corporation. (While "Stringray" is a trademarked name and particular product, it has entered the technical lexicon as a generic term, like Kleenex or Xerox.) In nearly every sales agreement , that firm has required law enforcement agencies to sign nondisclosure agreements forbidding them from discussing whether or not an agency even possesses such a device, much less describing its capabilities.

The lawsuit was filed last Friday by Freddy Martinez, a 27-year-old Chicagoan who works in the software industry. “Part of a well-functioning democracy is when people take the initiative to find out what their government is up to,” Matt Topic, Martinez’ lawyer, told Ars.

The Chicago Police Department did not immediately respond to Ars’ request for comment.

Staying mum

“This is an instance of a real lack of transparency by a law enforcement agency that is supposed to be enforcing the law," Topic said. "Mr. Martinez is clearly entitled to a response. What they did instead was that they acknowledged the request and he followed up for two months and they did not respond to him. At that level it’s an important case about transparency, and the government has to comply with open records statutes, and in particular the police department. There have been reports of this technology being used in other states. The Chicago Police has a long history of surveillance under the Red Squad . This is a police department that has a history of doing some questionable surveillance and some of that was found to be illegal.”

On March 22, 2014, Martinez made a request under the Illinois Freedom of Information Act (FOIA), asking the Chicago Police Department to provide “any records pertaining to the purchase or reception of any IMSI catchers, commonly known as Stingrays (a trademark of Harris Corporation).”

When the CPD did not respond after the five days it's allowed under the law, Martinez e-mailed the agency again. On April 1, the agency responded that it had received his request and noted, “We expect to have a response to you this week.”

On April 11, Martinez wrote back to the CPD and received no response. Five weeks later, he inquired again and received no reply. The Cook County lawsuit asks the court to find that the CPD made a “willful violation of FOIA” and that the police need to turn over the records.

Martinez told Ars that he became particularly interested in stingrays while attending the Day We Fight Back protest in Chicago in February when he and other privacy advocates noticed what they thought were newly installed cell equipment adjacent to unmarked police cars.

“[The use of stingrays] is something we can’t prove, but it’s a motivation,” he said. “Where are they being used? And if they’re being used to target people politically? I don’t like being tracked. I don’t like being surveilled. It’s important that people know what their governments are doing because if they don’t know what they’re doing, they can’t consent to it, and they can’t disagree.”