Last fall , a judge in Charlotte, North Carolina, unsealed a multi-case set of 529 court documents that detail the use of a stingray, or cell-site simulator, by local police. After that, the Mecklenburg County District Attorney’s office set out to review the applications and determine which records needed to be shared with defense attorneys.

The DA's office released a statement Friday saying its review is complete, and the county’s top prosecutorial authority found that "only two cases" involved the use of stingrays "for investigative purposes," meaning defense attorneys should be notified.

However, the report is not that simple. The DA review excluded cases that were "dismissed, resulted in a not-guilty verdict, or were federally charged." In total, only 149 cases were examined. The local Charlotte-Mecklenburg Police Department (CMPD) confirmed that stingrays were used in more than 20 percent of these (39 cases), but in 38 of those 39 instances, "the device was used to locate a defendant who already had a warrant for his arrest, and only one was used for investigative purposes."

As for the other 110 cases examined, the DA determined stingrays weren't used in 70 instances. That means in 40 cases, police were unable to confirm or deny stingray use.

As the DA stated:

Although prosecutors were not able to obtain information as to whether cell site simulators were definitively used in 40 cases, prosecutors examined the language in the motions to determine whether CMPD sought the orders for investigative purposes or for merely locating a defendant who had already been charged with a crime. Of those 40 cases, only one order was apparently sought for investigative purposes. It remains unclear whether this data was collected by a cell site simulator or another investigative technique. The DA’s Office then reviewed the files of the two cases—one that CMPD confirmed the use of a cell site simulator and one that CMPD could not determine whether the device was used—in which court orders were sought for investigative purposes.

While the District Attorney for Mecklenburg County office covers Charlotte, this review was the first time the DA office saw these CMPD stingray applications.

“The wall of secrecy is crumbling”

Stingrays can determine a specific phone’s location, but they also have the ability to intercept calls and text messages. And during the act of locating a phone, stingrays can sweep up information about nearby phones as well. Earlier this month, Ars reported on how the FBI is actively trying to “prevent disclosure” of stingray use in local jurisdictions across America.

Relatively little remains known about how stingrays are used by law enforcement agencies nationwide, although documents have surfaced. The public has learned how these devices have been purchased and used in some limited instances. In 2013, Ars reported on leaked documents showing the existence of a body-worn stingray. Back in 2010, Kristin Paget famously demonstrated a homemade device built for just $1,500.

While two US senators revealed the FBI’s position that the agency could use stingrays in public places without a warrant, other authorities have kept quiet on the subject. Cops have continually lied to courts about the use of such technology. And the largest manufacturer of the devices, the Harris Corporation, has been tight-lipped about its hardware capabilities.

Ars shared the Mecklenburg County DA's statement with a handful of legal and policy experts, and no one appeared impressed with the situation. Catherine Crump , a law professor at the University of California, Berkeley, told Ars that while the idea behind such a review was "laudable," it wasn’t conducted particularly well.

"It appears that the applications and orders to engage in cell tracking were so broad that they encompassed a number of different techniques," she e-mailed. "This is problematic, because it likely means that judges didn’t have a full picture of the conduct they were authorizing. It also probably explains why there is now no paper trail about what techniques were actually used in a subset of the cases."

ACLU tech and privacy analyst Chris Soghoian saw the message as a "no harm, no foul" cry. However, he sees even this small disclosure as another tiny crack in the mountain of secrecy surrounding stingrays nationwide.

"What's been fascinating about that and with [the recent case in] Erie County, the wall of secrecy is crumbling," he said. "It isn't happening with FBI, it’s through state courts and other agencies like FCC, and the more info that trickles out, it becomes tougher and tougher for FBI to hold the line."