State of Maryland v. Andrews is the first case in the country (that we know of) where an appellate court has held the Fourth Amendment precludes using a cell-site simulator (commonly known as a Stingray) without a warrant.
In the case, Baltimore Police used a Hailstorm—a device from the same company that makes Stingrays—to locate Kerron Andrews, the defendant, within a specific apartment. The police not only failed to get a warrant to use the device, they also failed to disclose it to the judge in their application for a pen register order. And it appears they even failed to tell the State’s attorney prosecuting Mr. Andrews’ case. The judge granted the defense’s request to suppress all evidence the police were able to get as a direct result of using the stingray and held the use of the device without a warrant violated Andrews’ Fourth Amendment right to be free from unlawful searches and seizures.
The State of Maryland appealed the judge's ruling to the Maryland Court of Special Appeals, and EFF joined the ACLU, and ACLU of Maryland in filing an amicus brief in support of Mr. Andrews. In 2016, the appellate court ruled for Mr. Andrews and upheld the lower court's order suppressing the evidence.