The judge also ruled that the government was not in the wrong for failing to disclose to a magistrate judge that it planned to use a stingray to track the defendant, or to explain to the judge how the tracking device it intended to use worked. He characterized this information as a “detail of execution which need not be specified.”

“When the government is seeking a warrant to use new technology, it has the duty to explain to the court what that technology is and how it works,” she said. “Stingrays are a very potent example of why that is so, because it scoops up innocent information of third parties who are not under probable cause surveillance.”

As some of you may be aware, our office has been working closely with the magistrate judges in an effort to address their collective concerns regarding whether a pen register is sufficient to authorize the use of law enforcement's WIT technology (a box that simulates a cell tower and can be placed inside a van to help pinpoint an individual's location with some specificity) to locate an individual. It has recently come to my attention that many agents are still using WIT technology in the field although the pen register application does not make that explicit.

While we continue work on a long term fix for this problem, it is important that we are consistent and forthright in our pen register requests to the magistrates…

In a February hearing, according to a transcript, Judge Campbell asked the prosecutor, "Were there warrants obtained in connection with the use of this device?"

The prosecutor, Frederick A. Battista, said the government obtained a "court order that satisfied [the] language" in the federal law on warrants. The judge then asked how an order or warrant could have been obtained without telling the judge what technology was being used. Mr. Battista said: "It was a standard practice, your honor."

Judge Campbell responded that it "can be litigated whether those orders were appropriate."

LAPD refuses to discuss how it uses the powerful tool, perhaps copying the FBI's playbook, which argued in the Rigmaiden case that revealing too many details would cause serious harm to future investigations.

The department, through a spokesperson, refused to comment on the device, despite repeated requests from the Weekly. Through the department's Discovery Unit, which handles requests from the public and media under the California Public Records Act, LAPD also declined to reveal any information on how the devices are used.

LAPD even refuses to say whether its detectives are required by police chief Charlie Beckand the Los Angeles Police Commission — all of whom are appointed by Mayor Antonio Villaraigosa — to obtain a search warrant before the StingRay is deployed against unsuspecting L.A. residents' cellphones.

Documents obtained from the Inspector General's office of the Department of Homeland Security reveal that LAPD bought two so-called "IMSI catchers" around 2006. At the time, LAPD had "recently purchased a cellphone tracking system (CPTS) for regional, terrorist-related investigations." The records mention StingRay and KingFish, brand names for IMSI devices made by Florida's Harris Corp.

Separate documents show that, in April 2010, the Los Angeles City Council approved the purchase of $347,050 in additional "StingRay II" equipment — and paid for it with outside funds from the Los Angeles Police Foundation, a nonprofit group that supports police functions, over which the city has no control.

Mobile devices connect to the wider network by using the antennae closest to them at the time. But when LAPD fires up a StingRay, it's often the most powerful signal in the area. Instantly, the department's spy equipment becomes the go-to "tower" for every cellphone and mobile device nearby — not just the phone carried by the suspect they're tracking.

"If the government shows up in your neighborhood, essentially every phone in the neighborhood is going to check in with the government," Soghoian warns. "It's almost like Marco Polo — the government tower says 'Marco,' and every cellphone in the area says 'Polo.' "

In a February hearing, according to a transcript, Judge Campbell asked the prosecutor, "Were there warrants obtained in connection with the use of this device?"

The prosecutor, Frederick A. Battista, said the government obtained a "court order that satisfied [the] language" in the federal law on warrants. The judge then asked how an order or warrant could have been obtained without telling the judge what technology was being used. Mr. Battista said: "It was a standard practice, your honor."

Judge Campbell responded that it "can be litigated whether those orders were appropriate."

The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.