(Reuters) - Baltimore police used secret cell phone surveillance technology more than 4,000 times in recent years under directions from the FBI not to tell courts about its use, an officer testified on Wednesday according to media reports.
The news comes as courts wrestle with cellphone privacy and potential violations of the Fourth Amendment of the U.S. Constitution that protects citizens from unreasonable searches and seizures of property by the government.
Baltimore police detective Emmanuel Cabreja testified that the FBI told prosecutors to drop cases involving the "stingray" technology if they were pressed too hard about the device, the Baltimore Sun reported.
Stingray devices imitate cell phone towers, making phones send identifying information.
Cabreja also said the police department was instructed to contact the FBI if judges or lawmakers began to ask questions, according to the Sun. He said the department had used the latest version of the stingray -- dubbed Hailstorm -- about 4,300 times since 2007, the newspaper reported.
Reuters could not independently verify the report. The FBI and Baltimore Police Department were not immediately available for comment.
The Sun published online what it said was a copy of the non-disclosure agreement between the FBI and police department outlining terms for using the technology.
The document said revealing details of the device -- even in criminal trials -- would "adversely impact criminal and national security investigations."
Florida's Supreme Court ruled in October that police must get warrants to track criminal suspects by monitoring their cellphone location signals.
(Reporting by Curtis Skinner in San Francisco; Editing by Andrew Heavens)