Anaheim police have been secretly using cell phone surveillance devices since at least 2009, according to the American Civil Liberties Union of Northern California, citing documents obtained following the filing of a public records lawsuit. The technology was made available to other Orange County police departments outside Anaheim as well, according to the ACLU.

"[These devices range] from devices that can be placed in an airplane and flown above the city, or put in a van and driven around buildings or through neighborhoods," ACLU of Northern California attorney Matt Cagle told KPCC. Cagle is a technology and civil liberties policy attorney. "We think that because these devices can peer inside of constitutionally-protected spaces, such as homes, they risk invading reasonable expectations of privacy that our Constitution protects."

The devices simulate a cell phone tower, Cagle said, communicating with phones and gathering information about the phones, their users and their locations.

"We don't think any surveillance devices, particularly these sorts of invasive cell phone surveillance devices, should ever be acquired or used without intense public debate and the adoption of safeguards to ensure they are only used in ways that follow our Constitution and laws," Cagle said.

One of the devices, known as a "dirtbox," was previously known to be used by the federal government, as well as Los Angeles and Chicago, according to the ACLU. It was purchased by the Anaheim Police Department using a federal grant in 2009.

"There is very little information about how the federal government and those other cities have used dirtboxes, and these documents raise a lot of questions about how Anaheim used their own dirtbox," Cagle said. He also raised questions about what sort of surveillance other cities in California and across the country may be using.

The Anaheim PD later acquired another cell-phone surveillance device known as a Stingray in 2011, as well as upgrading it in 2013. In late 2013, Anaheim purchased a hand-held cell phone surveillance device which, according to the ACLU, can locate phone signals in hard-to-reach places such as inside buildings.

The documents cited by the ACLU to show Anaheim's use of cell phone surveillance devices were released following the filing of a public records lawsuit. The documents have been heavily redacted. They do not show whether Anaheim police received warrants before using the devices, according to the ACLU, but the records note that Anaheim does obtain a "court order" or "court approval" for using the devices.

The ACLU received the documents due to an interest in how law enforcement agencies were seeking out surveillance tools, often using federal grant money, Cagle said.

When contacted by KPCC, the City of Anaheim declined to comment due to pending litigation.

Read the full documents obtained by the ACLU of Northern California below:

Full Anaheim documents