Documents obtained by the American Civil Liberties Union have shown that US cops are using the FBI's Stingray mobile phone tracking tech much more often than first thought.

And the Feds are going to great lengths to hide the full extent of its use.

"The documents paint a detailed picture of police using an invasive technology – one that can follow you inside your house – in many hundreds of cases and almost entirely in secret," said Nathan Freed Wessler, staff attorney at the ACLU.

"The secrecy is not just from the public, but often from judges who are supposed to ensure that police are not abusing their authority. Partly relying on that secrecy, police have been getting authorization to use Stingrays based on the low standard of 'relevance,' not a warrant based on probable cause as required by the Fourth Amendment."

The ACLU requested information about Stingray use from three dozen Florida police departments and found out that the system has been in use in the Sunshine State since 2007 – much earlier than first thought.

According to a May 2014 email, the Stingray system has been used in 1,835 cases in Florida, none of which were national-security related. More than a third of cases using the technology involved robbery, burglary, and theft, and the rest were largely "wanted persons" cases.

The ACLU found that police seldom sought a warrant before deploying Stingray, and in those cases where they did apply for a warrant, the specific technology used to track down a suspect's phone was never ever mentioned. Even in depositions, the police used only vague phrases like "electronic surveillance measures" and "confidential intelligence."

Scarface this isn't

The documents also included details of a few specific cases where Stingrays have been used. In one, defense lawyers were able to use the FBI's reluctance to reveal details about the technology to get a sweetheart deal of a sentence for their clients.

In March 2013, Tadrae McKenzie and two accomplices were accused of holding up a marijuana dealer and stealing his stash and his iPhone at gunpoint at a Florida Taco Bell. The dealer, identified by the Washington Post as Jamal Williams, said McKenzie threatened to "put a hole" in him with a handgun, while an accomplice wielded what looked like a shotgun.

Williams fled the scene and complained to police, who obtained a court order for Verizon phone data in the area and started digging. Two days later, McKenzie was stopped by police, who found marijuana in his car and arrested him. Upon questioning, McKenzie coughed up to the earlier robbery and informed on his two compadres.

This wasn't a major bust. The value of the stolen stash was estimated at $130 and the weapons used turned out to be semi-harmless BB guns, rather than the real thing. But it was enough to charge all three with robbery with a deadly weapon, which carries a minimum four-year prison sentence.

McKenzie's lawyer, however, got curious about how police had made their collar. In a deposition, a police investigator admitted that Verizon's location triangulation data alone had not been enough to find McKenzie. He said that a police technical specialist had tracked the alleged robber's mobe more directly – but he couldn't say how.

"I can't address it because I don't know the magic behind it," the investigator said.

The defense attorney then deposed the technical specialist in question, who explained that the police had used a cell-tower simulator that could locate a specific handset. But he wouldn't go into any more detail – refusing even to give the device's model number – saying the technology was covered under a non-disclosure agreement.

"It is not nearly as invasive or as sinister as it is sometimes characterized to be," the specialist said. "I so wish that I could tell you how this equipment operates, because I think I could put so many people at ease. Unfortunately, I am not able to do that."

The defense lawyers called for the case to be thrown out, on grounds that this kind of search was a breach of their clients' Fourth Amendment rights. They also successfully subpoenaed to have the scanning equipment brought into court.

Two days before the device was due to appear, however, prosecutors offered a sweetheart deal. McKenzie pled guilty to a second-degree misdemeanor in exchange for six months' probation, while his accomplices got sentences of two years – suspended – and walked free.

What's the big deal?

The ACLU believes the technology used in McKenzie's case was the FBI's Stingray system. Available in handheld, truck mounted, or airborne versions, Stingray impersonates a mobile cell tower and orders all handsets in the area to report their International Mobile Station Equipment Identity (IMEI) numbers.

The case highlights quite how far the FBI is willing to go to keep the technology secret. It only came to light a couple of years ago in an identity fraud case, and the FBI has remained close-lipped on the topic since.

The agency is known to share the scanners with local police forces, however, and although those who do are contractually bound to secrecy, work by the ACLU has shown the surprising extent to which is it being used. The incomplete records obtained from Florida even showed that Florida police departments were sharing the technology with departments in other states.

In some cases, Florida police departments were very unwilling to share information on the system. One denied using Stingray outright, then later admitted it did – but not without sending the ACLU a bill for $20,000 in "discovery fees" for copies of a series of pages from its website.

Still, increasing awareness of Stingray's use – and how seldom police obtain properly issued search warrants for its use – could be a boon to defense attorneys in the future, if they play their cards right. ®