Brad Heath

USA TODAY

Lawyers in Baltimore have identified as many as 200 people who were sent to prison based on evidence police gathered with the help of a powerful cellphone tracking tool that a state court has now ruled was used illegally.

The ruling, issued Wednesday by Maryland’s second-highest court, said Baltimore police violated the Constitution when they used one of the tracking devices to catch a shooting suspect without first obtaining a search warrant. It was the first time an appeals court had weighed in directly on the legality of phone-trackers that have been widely — and mostly secretly — used by police agencies for nearly a decade.

“Cellphone users have an objectively reasonable expectation that their cellphones will not be used as real-time tracking devices, through the direct and active interference of law enforcement,” a panel of three judges on Maryland’s Court of Special Appeals wrote. The judges also accused Baltimore authorities of misleading the lower-court judge who had approved their use of the device, commonly known as a stingray.

That decision could imperil hundreds of criminal convictions in Baltimore and elsewhere in Maryland, where police have used stingrays prolifically. An investigation last year by USA TODAY identified nearly 2,000 cases in Baltimore alone in which the police had secretly used stingrays to make arrests for everything from murder to petty thefts, typically without obtaining a search warrant.

“We have a grave concern that our clients are incarcerated because of the use of a stingray that was illegal,” said Natalie Finegar, who is coordinating a review of stingray cases for the city’s public defender.

Cellphone Surveillance - USATODAY.com

Finegar said defense lawyers are focused most urgently on about 200 cases in which people appear to have been sent to prison based on evidence the police found after they used a stingray. “Those are the emergencies,” she said. “By itself, it’s just a huge number of cases."

Stingrays are suitcase-sized devices that allow the police to pinpoint a cellphone’s location to within a few yards by posing as a cell tower. They have drawn alarm from privacy advocates, in part because they also can intercept information from the phones of nearly everyone else who happens to be nearby.

Dozens of police departments from Miami to Los Angeles own stingrays, but few have revealed when or how they use them, in large part because they signed nondisclosure agreements with the FBI. As a result, few courts have weighed in on the circumstances in which the police are permitted to use them.

The U.S. Justice Department last year ordered federal agents to obtain search warrants before using stingrays.

Cellphone data spying: It's not just the NSA

Maryland prosecutors can ask the state’s highest court to overturn Wednesday’s decision. Christine Tobar, a spokeswoman for the state’s attorney general, said it was “reviewing and evaluating next steps.”

Even if it stands, the legal road for people imprisoned on the basis of what the judges declared to be an illegal search is far from straightforward. State law puts strict limits on when and how people serving prison sentences can challenge their convictions.

“This isn’t some kind of get out of jail free card. It might be different case by case,” American Civil Liberties Union lawyer Nathan Wessler said. “What’s clear from this opinion is that this secrecy cannot stand.”

A Baltimore detective testified last year that police had used their tracking device about 4,300 times since 2007.

Wednesday’s court opinion came in the case of Kerron Andrews, who was charged in a 2014 shooting. A city judge gave the police a “pen register” order — a court order that does not require the same level of proof as a search warrant — authorizing them to use a stingray to find him. Maryland’s Court of Special Appeals ruled that because police had not obtained a search warrant, prosecutors could not make use of the evidence they found when Andrews was arrested.

The judges announced their decision nearly a month ago, but did not lay out their reasoning or the legal problems with Baltimore’s surveillance until they delivered a 74-page opinion on Wednesday.

A Baltimore court ordered Andrews freed on bond while the state decides whether to appeal. His lawyer, Assistant Public Defender Deborah Levi, said he could be freed as soon as Friday.