The American Civil Liberties Union is asking appellate judges to force the Tucson Police Department to release information about devices that allow them to track cell phones and, by extension, their users.

The fight is over a device called StingRay. It relies on the fact that cellphones essentially log in with each tower they are near, so incoming calls are routed to the correct tower and ongoing calls are handed off from tower to tower as someone travels through an area.

Because the device mimics a cell tower, every phone within range logs in. Police then can comb through that data to find the cellphone they want. The device is portable and officers can take it door to door to pinpoint the phone for which they are searching.

The ACLU is representing a freelance journalist who wants things materials like training manuals and other documents from Tucson police on how they use the equipment. A trial judge rejected the request, accepting the city's explanation that would disclose sensitive investigative techniques.

Attorney Dan Pochoda with the ACLU of Arizona said that's not enough.

You can't just invoke the term 'sensitive information' or 'investigative techniques,' and therefore, that trumps any rights you have under the Arizona Public Records Law,” Pochoda said. “That's what happened here.”

He said Arizona has a stronger public records law than most other states.

“For every request, there has to be a specific showing related to that specific request as to why there would be harm to the public interest if it was disclosed,” Pochoda said.

What the appellate court rules is likely to have statewide implications, setting precedents for how much leeway courts will give all Arizona governments to keep documents secret