Washington could be the next U.S. state to limit police use of the controversial Stingray surveillance technology. Both chambers of the state Legislature have approved a bill that would require police to obtain a warrant before using the device to collect information on thousands of cell phones as officers sweep through an area in pursuit of a suspect.

Stingrays, manufactured by Florida company Harris Corp., are suitcase-sized boxes that enable police to replicate the signal from a cell phone tower. When a Stingray-equipped patrol car cruises through an area, many of the phones in that area automatically connect to the Stingray instead of the nearest cell tower. That means police gain instant access to all kinds of phone information that they normally would need to a warrant to obtain, such as snippets of phone conversations, location data, text message metadata and other sensitive material.

Federal and local police in at least 18 states use Stingrays with little or no legal oversight. In order to obtain a Stingray device, each agency must sign a nondisclosure agreement with Harris, a defense contractor that supplies telecommunications equipment to the military.

Eight states -- including Illinois, Virginia and Maryland -- have passed laws specifically requiring law enforcement to use a warrant in order to track communications in real time. Washington could be the ninth state to enter that category after the state's House and Senate both voted unanimously to approve HB 1440. The proposal next goes to the desk of Democratic Gov. Jay Inslee, who has until May 13 to sign or veto it. When contacted by phone, a representative from Inslee's office said the governor's staff was “still analyzing the contents of the bill.”

HB 1440 was drafted in response to separate controversies in Seattle and Tacoma, the state's largest and third-largest cities, when local lawmakers and at least one judge expressed surprise and reservations when informed about the investigative measures used in their jurisdictions. Police in Washington state are typically required to obtain a court order to prove the desired information is relevant to an investigation before using a Stingray. A search warrant requires police to demonstrate probable cause, a more difficult task.

“I think there's been a larger trend in the last few years for the state legislatures to start thinking about electronic privacy protections,” said Hanni Fakhoury, a senior staff attorney at the Electronic Frontier Foundation, a digital rights advocacy group. “All this bill is saying is that if you're going to use it you have to get a warrant, which means you can use it. And most states have statutes that say you don't need a warrant if it's an immediate life-threatening situation.”

The bill reaches Inslee's desk as a Washington state defendant who was arrested with help from a Stingray was preparing to argue that police, by using a Stingray, violated his Fourth Amendment right against unreasonable search and seizure. Where attorneys in other states have dropped charges rather than reveal Stingray details, though, Washington prosecutors didn't oppose the defendant's claim. The police failure to obtain a court order before using the Stingray led to the dismissal of evidence gathered by the device without objection from the prosecution.