A police department in Florida failed to tell judges about its use of a cell phone tracking tool "because the department got the device on loan and promised the manufacturer to keep it all under wraps," the American Civil Liberties Union said in a blog post today.

The device was likely a "Stingray," which is made by the Florida-based Harris Corporation. Stingrays impersonate cell phone towers in order to compel phones to "reveal their precise locations and information about all of the calls and text messages they send and receive," the ACLU noted. "When in use, stingrays sweep up information about innocent people and criminal suspects alike."

The tracking technology was used by the Tallahassee Police Department in September 2008 to locate a man accused of rape and the theft of a purse, which contained the alleged victim's cell phone. The man, James L. Thomas, was convicted of sexual battery and theft, but he filed an appeal "contending that evidence obtained in violation of the Fourth Amendment, and article I, section 12 of the Florida Constitution, was introduced against him at trial," according to a court ruling in November 2013 that reversed the conviction and ordered a new trial.

Police "did not want to obtain a search warrant because they did not want to reveal information about the technology they used to track the cell phone signal," the District Court of Appeal ruling said. "The prosecutor told the court that a law enforcement officer 'would tell you that there is a nondisclosure agreement that they’ve agreed with the company.'"

The appeals court agreed that police violated the Fourth Amendment and Florida constitution and that the "trial court erred in failing to suppress the evidence obtained as a result of the violation."

The ACLU is trying to find out just how extensive the use of the cell phone tracking technology is. Last week, the organization "fil[ed] a motion for public access to sealed records in state court and submitt[ed] public records requests to nearly 30 police and sheriffs’ departments across Florida seeking information about their acquisition and use of stingrays," the ACLU said. The sealed records are of a transcript from a hearing on August 23, 2010 that considered Thomas' motion to suppress evidence and compel disclosure of evidence.

The ACLU summarized the Thomas case as follows:

As revealed in a recent opinion of a Florida appeals court, Tallahassee police used an unnamed device—almost certainly a stingray—to track a stolen cell phone to a suspect’s apartment. They then knocked on the door, asked permission to enter and, when the suspect’s girlfriend refused, forced their way inside, conducted a search, and arrested the suspect in his home. Police opted not to get warrants authorizing either their use of the stingray or the apartment search. Incredibly, this was apparently because they had signed a nondisclosure agreement with the company that gave them the device. The police seem to have interpreted the agreement to bar them even from revealing their use of stingrays to judges, who we usually rely on to provide oversight of police investigations. When the suspect’s lawyer tried to ask police how they tracked the phone to his client’s house, the government refused to answer. A judge eventually forced the government to explain its conduct to the lawyer, but only after closing the courtroom to the public and sealing the transcript of the proceedings so the public and the press could never read it. Only later, when the case was heard on appeal, did the most jaw-dropping fact leak out. As two judges noted during the oral argument, as of 2010 the Tallahassee Police Department had used stingrays a staggering 200 times without ever disclosing their use to a judge to get a warrant.

In its blog post, the ACLU argued that "Potentially unconstitutional government surveillance on this scale should not remain hidden from the public just because a private corporation desires secrecy. And it certainly should not be concealed from judges."

In another case from a year ago, Justice Department e-mails obtained by the ACLU revealed "that the Feds were not fully clear about the fact that they were specifically using stingrays (also known as “IMSI catchers”) when asking for permission to conduct electronic surveillance from federal magistrate judges," as we reported at the time.