(TNS) -- Police agreements with the Federal Bureau of Investigation ask officers to hide the capabilities of high-tech surveillance equipment from the courts and the public, according to records obtained by the ACLU.

Unknown is whether the Tacoma Police Department’s agreement with the feds to operate its cellphone-tracking device has such a provision. But even if it does, police officials say their officers now tell judges when using their device, called a cell site simulator or Stingray.

This week’s release of an unredacted copy of the nondisclosure agreement the FBI makes police agencies sign before acquiring such technology came after a court ordered the Erie County Sheriff’s Office to turn over documents to the New York Civil Liberties Union.

One section of the agreement requires police to keep the use of the device secret, even if judges or defense attorneys ask for more information.

Police in Tacoma and elsewhere have used the device for years. It tricks cellphones into connecting with what appears to be a cell tower. Using the device, police can more accurately pinpoint the location of a suspect by the cellphone he or she carries. The device can also draw in data from all cellphones in an area, though Tacoma Police have said they don’t use it that way.

The Tacoma Police Department’s nondisclosure agreement with the FBI was provided to The News Tribune last year, but it was heavily redacted. In a response to an identical records request to the FBI, the agency would not confirm nor deny the existence of a nondisclosure agreement with Tacoma.

The NDA between the FBI and Erie County Sheriff’s Office tells police to hide the use of cell site simulators from judges, prosecutors and defense attorneys, unless the agency gets written permission from the FBI. The Associated Press has also uncovered an unredacted copy of a 2011 agreement between the FBI and the Baltimore Police Department that has identical provisions.

After The News Tribune reported last year that Tacoma police possessed a Stingray, Pierce County Superior Court judges demanded police to specific in court orders when they intended to use the technology. They also made police promise to not keep data collected on non-suspects.

Tacoma Assistant Police Chief Kathy McAlpine said via email Thursday that the judges’ wishes are being honored: “Cell site simulator is in all of our requests for court orders.”

The department has asked for eight court orders since the beginning of the year, all for TPD suspects, she wrote.

Pierce County Superior Court Judge Ronald Culpepper said he has not signed one of the eight court orders, but there are 22 judges and any one of them could have signed orders.

“I have not seen (orders) where we were told this was being used since the story came out,” he said, referring to a story in The News Tribune in August that revealed the police use of the technology.

The Baltimore Sun provided a rare glimpse into how the technology works this week in coverage of a court hearing where a detective described how the Hailstorm, the latest version of the Stingray, works:

Cabreja said the device allows police to make a stronger signal emanate from the phone to help them find it.

"It, on screen, shows me directional arrows and signal strength, showing me the phone's direction," he testified.

The detectives traced the phone to a group home and knocked on the door. They told the woman who answered that they were conducting a general criminal investigation and asked to come inside, Cabreja said, and the woman agreed.

Seven detectives entered the home, he said. They used the Hailstorm to make the phone ring before anyone knew why they were really there.

Tacoma police also have the Hailstorm, which the department bought in 2013 for $109,421 from Harris Corp. of Florida.

While there are no laws governing how police in Washington state use cell site simulators, that could soon change. Legislators are considering a bill that would require police to get permission from judges to use the technology, along with a few other limitations.

The Tacoma Police Department says its officers already follow the rules set forth in the proposed legislation.

©2015 The News Tribune (Tacoma, Wash.) Distributed by Tribune Content Agency, LLC