The New York Police Department (NYPD) has used the covert cell phone spying devices known as Stingrays more than 1,000 times since 2008, including for the investigation of low-level crimes and typically without a warrant, the New York Civil Liberties Union (NYCLU) revealed on Thursday.

“If carrying a cell phone means being exposed to military grade surveillance equipment, then the privacy of nearly all New Yorkers is at risk,” said Donna Lieberman, NYCLU executive director. “Considering the NYPD’s troubling history of surveilling innocent people, it must at the very least establish strict privacy policies and obtain warrants prior to using intrusive equipment like Stingrays that can track people’s cell phones.”

Thursday’s revelations are the first time the extent of the police department’s use of the devices has been made public. According to internal documents (pdf) obtained by the NYCLU through a Freedom of Information Act (FOIA) request, the NYPD deployed Stingrays as many as 200 times a year.

In addition, the department confirmed that it has no written policy for the devices, but that its practice is to obtain a pen register order—which requires a lower standard of probable cause to collect phone data than a warrant—prior to using them.

Stingrays operate by mimicking cell phone towers, tricking nearby cell phones into connecting with them, which allows police to pinpoint users’ locations, collect phone numbers that a user has been calling or text messaging, and even intercept the contents of their communications. Civil rights groups have criticized the controversial technology for what they say are invasive and unconstitutional methods.

The devices were most often used in the investigation of serious offenses, such as homicide, rape, and other violent crimes, but also for crimes like identity theft and money laundering. Other instances were even more dubious.