Civil liberties groups are bracing for a battle as British Columbia’s privacy commissioner launches an inquiry into a device that allows police to secretly monitor mobile phones.

British Columbia’s privacy commissioner has launched a closed-door inquiry into the public’s right to know about Stingray, a high-tech tool that mimics a cellphone tower and tricks phones in order to scoop up everyone’s data in range, and potentially store it all.

Stingray is part of mass surveillance systems that police are fighting to keep secret.

Micheal Vonn, of the B.C. Civil Liberties Association, says Stingray should not be used by law enforcement.

“What we’re saying here is, does it help to collect the data of tens of thousands of individuals that aren’t the subjects of police investigation?” Vonn said in an interview with CTV Vancouver. “No, of course it doesn’t help.”

U.S. federal agencies as well as dozens of local departments have been deploying the spying device for a decade now. But new American laws are restricting its use.

But in Canada, law enforcement from Quebec RCMP to Vancouver police are battling any disclosure.

Police in Vancouver have not confirmed whether they use Stingray. In a statement, Vancouver Police Const. Brian Montague said, “We never discuss or provide information regarding investigative techniques or police tactics.”

Criminal defense lawyer Matt Nathanson says the stakes are high and revelations regarding Stingray use could see courts flooded with conviction appeals.

“In my view, this is patently unconstitutional and if this matter will be litigated before the courts, I think the courts would be very clear in their condemnation of it,” Nathanson said.

With files from CTV Vancouver’s Tom Popyk