A stingray, made by Harris Corp. U.S. Patent and Trademark Office

The police department in Erie County, New York fought hard to prevent the New York Civil Liberties Union from obtaining records about its use of a controversial surveillance tool known as a stingray.

The reason why may be because of what the records show: that cops in that county, which includes the city of Buffalo, used the devices 47 times since 2010 but only once sought and obtained a court order to do so. That revelation contradicts what the county sheriff said last year when he asserted that the department only used the devices under "judicial review."

In the single case in which police sought permission from a court, they asked for a court order rather than a warrant, which carries a higher burden of proof. And in their request, they mischaracterized the true nature of the tool.

“These records confirm some of the very worst fears about local law enforcement’s use of this expensive and intrusive surveillance equipment.”

The records, which the NYCLU published in a blog post today, also show that the county sheriff's office signed a stringent gag order with the FBI to maintain secrecy about their stingray records. The department was told to withhold information about the devices in any documents filed with courts, such as affidavits and other documents describing how they obtained evidence in criminal cases. The department was even told that the FBI maintained the right to intervene in county prosecutions to request criminal cases be dismissed if there was a chance that a case might result in the disclosure of information about law enforcement's use of stingrays.

“Stingrays are an advanced surveillance technology that can sweep up very private information, including information on innocent people,” NYCLU Western Region Director John Curr III said in a statement. “If the FBI can command the Sheriff’s Office to dismiss criminal cases to protect its secret stingrays, it is not clear how the $350,000 we are spending on stingray equipment is keeping the people of Buffalo safer.”

The revelations continue a trend in several states across the U.S. wherein law enforcement agencies have gone to great lengths to prevent the public from learning about their use of stingrays. The surveillance tool simulates a legitimate cell phone tower to trick mobile phones and other devices on a cellular network into connecting to the devices and revealing their location. Stingrays emit a signal that is stronger than the signal of other cell towers in the vicinity in order to force mobile phones and other devices to establish a connection with them and reveal their unique ID. Stingrays can then determine the direction from which the phone connected— a data point that can then be used to track the movement of the phone as it continuously connects to the fake tower.

Many police departments have signed non-disclosure agreements with the Harris Corporation, one of the leading makers of the devices, to prevent them from releasing records about the systems or discussing them. In Florida, the U.S. Marshals service went so far as to seize records about a local police department's use of stingrays in order to prevent the American Civil Liberties Union from obtaining them. And many law enforcement agencies have deceived judges about their use of the devices in order to prevent defendants and the public from learning about how they're being used.

Erie County similarly fought hard to prevent the NYCLU from obtaining these records but was ordered to turn them over by a court. The documents show that the sheriff's office used stingrays at least 47 times between May 1, 2010 and October 3, 2014. The one time the department sought judicial approval was in October 2014, contrary to what Erie County Sheriff Tim Howard said in May, 2014: that the devices were used under "judicial review" in all criminal matters, implying that investigators always seek court approval before using them.

Not only this, but the records show that when the department did seek a court order, they identified the spy tool they planned to use as a pen register device, not a stingray or cell site simulator. The use of the term "pen register device" is controversial. Law enforcement agencies maintain that stingrays operate like pen registers and are not invasive, but this doesn't paint the picture. Pen registers record the numbers dialed from a specific phone number, but stingrays are used primarily to track the location and movement of a device and can be much more invasive than pen registers. By describing the tool as a pen register device to the judge, the law enforcement agency was withholding information about the full capability of the device.

In fact, the public has yet to learn exactly how much these surveillance tools can really do, due to the secrecy around them. Recently, a federal agent admitted to a court that stingrays have the ability to disrupt cellular communications for any device in its vicinity, not just the ones targeted by law enforcement. And there are also stingray devices that have the ability to collect the content of phone calls, though U.S. law enforcement agencies have often insisted that the ones they use have this capability disabled.

Although there's still much more the public should know about how and when law enforcement uses this invasive spying tool, it's clear departments will continue to do everything in their power to keep the public, and judges, in the dark.