When a Maryland appeal's court recently ruled that police were wrong to use a secretive cell-phone tracking device known as a stingray without a warrant, civil liberties groups cheered over the clear privacy message the three-judge panel sent to law enforcement.

The judges concluded that authorities could not turn the cell phones people carry into real-time tracking devices without a warrant, shooting down the state's assertion that merely turning on a cell phone equaled consent to be tracked.

The written opinion, released by the judges last week (.pdf), is also important for a few other reasons: The judges upheld a lower court's decision to suppress evidence gathered with the help of the stingray, and they strongly rebuked the Baltimore police for concealing their use of the stingray from a judge when they applied for a court order to track the suspect.

Judges have been reluctant in the past to suppress evidence in cases where questions about Fourth Amendment protections were still unresolved at the time the evidence was collected. But the decision to do so in this case, despite the lack of a clear constitutional resolution when the evidence was collected, sends a potent warning to federal and local law enforcement agencies around the country: Deception around the use of stingrays is tantamount to judicial fraud and could cost them convictions, experts say.

"This is the first appellate opinion in the country to fully address the question of whether police must disclose their intent to use a cell site simulator to a judge and obtain a probable cause warrant," says Nathan Wessler, staff attorney for the ACLU's Speech, Privacy, and Technology Project.

The ruling is significant for another big reason—it, and other stingray cases expected to pop up in its wake, could ultimately push the issue to the Supreme Court, something civil liberties groups have been wanting since stingrays first came to public attention in 2011 with the Daniel Rigmaiden case.

There are some caveats around the Maryland ruling, however. The groundbreaking decision came from a state appellate court, not a federal appeals court, and is therefore not legally binding outside the Maryland state court system. And although the losing side in the Maryland case can try to take the case to the Supreme Court, Wessler says that higher court is not likely to take on the case unless another court in the country weighs in on stingrays and rules against the need for a warrant. It was that kind of split decision that sent the now-famous GPS tracking case, United States v. Jones, to the Supreme Court in 2011.

In the meantime, although the Maryland ruling isn't legally binding outside Maryland, its effects will still reverberate in other states, says Wessler.

"By being the first opinion really dealing with this issue, the Maryland court has set the tone for this debate ... and I would fully expect courts elsewhere in the country to very seriously look at this opinion as a starting point for their own analysis," he says.

Jennifer Lynch, a senior staff attorney with the Electronic Frontier Foundation who wrote an amicus brief in the Maryland case with Wessler, agrees.

"We’re starting to see other stingray cases bubble up, and it's pretty fantastic that the first opinion on this came out so strongly in favor of the defendant's Fourth Amendment rights," she says.

Background on the Maryland Case

The Maryland case, State v. Andrews, involves a shooting suspect named Kerron Andrews who fired at three people in April 2014 while they were attempting to buy drugs. Andrews was identified as the shooter and charged with attempted murder. In an attempt to locate him, Baltimore police used a Hailstorm to track his cell phone. Hailstorm is the brand name of a stingray device, the generic name for technology that masquerades as a legitimate cell tower in order to trick nearby mobile phones into connecting to it and revealing their unique device ID, which law enforcement agents can use to track the location and movement of the cell phone.

Police first obtained historical cell-site location data from Sprint, Andrews' phone carrier, as well as GPS data for his phone to determine his general location. That took them to the vicinity of a small apartment complex. To pinpoint the exact apartment where Andrews was, they used the Hailstorm. They found him inside lying on a sofa with the phone in his pocket. After subsequently obtaining a search warrant for the apartment, they found a gun under the sofa cushions.

Police did not get a probable-cause warrant to use the Hailstorm—instead they sought a court order (which doesn't require probable cause) for a pen-register/trap and trace device. Pen registers and trap-and-trace devices record the phone numbers called and received by a specific number, but cannot track the location of a phone. In their application, however, police described the technology they planned to use as a "Pen Register\Trap & Trace and Cellular Tracking Device to include cell site information, call detail, without geographical limits, which registers telephone numbers dialed or pulsed from or to the telephone(s) having the number(s)."

When Andrews' defense attorney later sought information about how they had located Andrews, prosecutors withheld the information, stating “[a]t this time the State does not possess information related to the method used to locate [Andrews] at 5032 Clifton Avenue.” Five months later, they acknowledged that police had used a stingray.

Andrews' attorney argued that using a tracking device that emits electronic signals through the walls of a building amounts to an unreasonable search under the Fourth Amendment and therefore required a warrant. The trial court agreed and suppressed all evidence police obtained from the residence, since they were only able to find the gun because the stingray had taken them to the apartment. The appellate court upheld the ruling.

In their opinion, the appellate judges rebuked prosecutors for concealing information about the technology they used to track the suspect. Baltimore authorities had withheld information about the stingray because the city had signed a non-disclosure agreement with the FBI in 2011, which stated that they could purchase and use a stingray only if they promised not to disclose information about the technology and their use of it "to the public in any manner including b[ut] not limited to: in press release, in court documents, during judicial hearings."

The issue is not unique to Maryland. Law enforcement agencies around the country have signed similar non-disclosure agreements with the FBI and with Harris Corporation, which is the equipment's primary manufacturer. As a result, agencies have withheld information about their use of stingrays from judges and defense attorneys. In some cases, they have intentionally deceived judges when seeking a court order, describing the technology only as a pen register device. When faced with forced disclosure by a court, federal prosecutors have even dropped charges against some defendants to avoid revealing information about their use of a stingray.

But the Maryland appellate judges found such gag agreements and deception to be “inimical to the constitutional principles we revere." In order to authorize a search, "it is self-evident that the court must understand why and how the search is to be conducted."

Wessler says the rebuke puts federal and local law enforcement agencies on notice that they will face consequences if they deceive courts. He also says the Justice Department's forced NDAs have put local police in a difficult position.

"The FBI has had a pretty cozy relationship with the non-disclosure agreements," says Wessler. "They’ve forced local police departments to sign off and let the locals do the dirty work of hiding this [information about stingrays] from judges. The FBI is now on very clear notice that this regimen of really incredible secrecy has to end. It’s not just a fraud on the court, it’s going to jeopardize state and local investigations in pretty large numbers."

That's particularly true in Maryland.

The Baltimore police have used stingrays more than 4,000 times since 2007, often to solve mundane crimes, such as to locate a stolen cell phone, a misdemeanor theft, or track the location of a woman who was making harassing phone calls.

At least 200 other cases involving convicted criminals in Maryland, as well as ongoing cases that involve the use of a stingray device, are now in question as a result of the appellate court ruling. And it will likely embolden defense attorneys around the country to pressure prosecutors to disclose their methods for locating defendants and challenge the use of stingray devices wherever they were used.

From Maryland to the Supreme Court, Someday

And Lynch says there's another issue at hand that wasn't really a focus of the appellate decision—the constitutionality of the NDAs themselves.

"You can’t be bound by a contract that requests you to do something that violates the Constitution," she says. "Without full information about the stingray, the defendant’s constitutional rights can be violated because they don’t have the opportunity to challenge the use of the stingray. The judge doesn’t put it in those terms, but due process is one of those [inimical] constitutional principles [we revere]."

It should be noted that last year, sensing the direction the legal and political winds were blowing, the Justice Department announced a new policy around the use of stingrays by federal law enforcement agencies. Under that policy, federal agents have to obtain a warrant to use stingrays and have to disclose their use to judges. But that policy does not cover local law enforcement. The Maryland court ruling is significant in that it extends the warrant requirement to local police and sheriffs departments—at least in Maryland.

Another problem with the Justice Department policy is that it's just a policy, not case law, and could prove to be fickle if the next administration changes its mind about warrants. "The Justice Department in that policy very explicitly says 'we're not conceding that that Fourth Amendment requires any of these protections, we're just doing this as a matter of policy,'" says Wessler. "They're keeping open the option to go back to not using warrants ... without conceding that that would ever violate the Constitution."

Wessler says a Supreme Court ruling requiring warrants is what's really required to solidify the constitutional protections around the use of stingrays. That's how the question around law enforcement's use of GPS trackers finally got resolved, and Wessler says this is the only way the stingray issue will be settled as well.

"Who knows if and when it will actually get to the Supreme Court, but it is the kind of issue that's going to percolate for a little while, and then could be a really good candidate for the Supreme Court to weigh in on," he says.