newly published e-mail from a Seattle police detective illustrates the bizarre situation that law enforcement finds itself in these days: apparently everyone knows about the cops’ use of stingrays, and yet no one can explain it.

The e-mails were published over the weekend by Andrew Charles Hendricks, a local privacy activist.

Stingrays, the common name for “cell-site simulators,” can be used to determine a phone’s location, but they can also intercept calls and text messages. During the act of locating a phone, stingrays also sweep up information about nearby phones—not just the target phone. Earlier this month, Ars reported on how the FBI is actively trying to “prevent disclosure” of how these devices are used in local jurisdictions across America.

As Detective Len Carver, who is also on an FBI task force, wrote to his colleagues in May 2014:

During a debrief with some of our group here, we learned that law enforcement's use of the "phone ping" in yesterday's abduction was released to the media. And, it was widely reported. Certainly, we (and the general public too) understand that law enforcement has the ability to "ping" a cell phone for its location; however, use of the technology is considered a sophisticated technique as well as "Law Enforcement Sensitive / Classified." It is important for us to keep this sophisticated technique confidential. In fact, RCW 9.73.260 requires the pleadings (and subsequent technique) to be filed under seal until further ordered by the court. Publicly discussing the technique is considered a substantial threat to the interests of effective law enforcement, to public safety, and, depending on the case, to victims or witnesses. By their very nature, authority to use the tools (pings and tracking) must remain covert to be effective. Public disclosure of the technique could render this investigative tool useless. It is standard practice for the FBI to require a law enforcement agency to complete a non-disclosure agreement prior to utilizing a sensitive and sophisticated technique. While there was no agency agreement in the referenced abduction matter, we do have a standing written non-disclosure agreement with the King County Prosecutor's Office.

In an e-mail to Ars, Carver wrote "I am not authorized to speak publicly about the investigative technique to which you referred in your voicemail," and suggested that we speak with a spokeswoman.

“Relevant to an ongoing criminal investigation”

In a later e-mail that was part of the same set of disclosed messages, one August 2014 e-mail from Detective Ed Troyer , a spokesman for the nearby Pierce County Sheriff’s Department, wrote to his colleagues: “If you don’t know [about] Stingray, PenLink and how we ping phones you should learn. All three are completely different ways of obtaining and using data.”

It’s not immediately clear how the Tacoma Police’s cellphone pings are taking place, or what device is being used to send them—it’s likely that it was through the stingray itself.

Troyer did not immediately respond to Ars’ request for comment, either.

Relatively little is known about how, exactly, the stingrays are used by law enforcement agencies nationwide, although documents have surfaced showing how they 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.

Worse still, cops have lied to courts about the use of such technology. In January 2015, two US senators made public the FBI’s position that the agency could use stingrays in public places without a warrant. The largest manufacturer of the devices, the Harris Corporation, has been tight-lipped about its hardware capabilities.

While the Tacoma Police Department has claimed that it gets a warrant every time it uses its stingray, it’s more likely that they are simply asking a judge to sign off on a “pen register, trap and trace order.”

In the pre-cellphone era, a “pen/trap order” allowed law enforcement to obtain someone's calling metadata in near real-time from the telephone company. Now, that same data can also be gathered directly by the cops themselves through the use of a stingray. In some cases, police have gone to judges asking for such a device or have falsely claimed a confidential informant, but in fact have deployed this particularly sweeping and invasive surveillance tool.

Most judges are likely to sign off on a pen register application, not fully understanding that police are actually asking for permission to use a stingray. Under both Washington state law and federal law, pen registers are granted under a very low standard: authorities must simply show that the information obtained from the pen register is “relevant to an ongoing criminal investigation.”

Getting a judge to sign off on a pen register is a far lower standard than being forced to show probable cause for a search warrant or wiretap order. A wiretap requires law enforcement to not only specifically describe the alleged crimes but also to demonstrate that all other means of investigation had been exhausted or would fail if they were attempted.

In the wake of the Tacoma News Tribune’s reporting on stingray use in Tacoma, in November 2014, judges there imposed stricter standards.

This past week, the Charlotte-Mecklenburg Police Department (CMPD) in North Carolina—one of the largest local police departments in the American South—revised its surveillance applications to judges, making its judicial requests to use cell-site simulators much more explicit for the first time.