A handful of United States senators have finally woken up to the questionable use of cell-site simulators, also known as stingrays.

In a letter sent Tuesday to Attorney General Eric Holder and Secretary of Homeland Security Jeh Johnson, 10 Democratic senators and Bernie Sanders (I-Vt.) posed some of the most direct questions about the digital surveillance devices.

The devices are often used covertly by local and federal law enforcement to locate target cellphones and their respective owners. However, stingrays also sweep up cell data of innocent people nearby who have no idea that such collection is taking place. Stingrays can be used to intercept voice calls and text messages as well.

Both manufacturers and law enforcement have been notoriously tight-lipped about precisely how such devices are acquired and implemented. Former federal magistrate judge Brian Owsley (now a law professor at Indiana Tech) has been unsuccessful in his efforts to unseal orders that authorize their use despite intimate familiarity with the legal system. And just last month, local prosecutors in a Baltimore robbery case even dropped key evidence that stemmed from stingray use rather than allow a detective to fully disclose how the device was used.

As the senators write:

We would like to know if your departments, or its components, utilize these devices along the borders and in our states. Accordingly, we request the following information: 1. To what extent does your department use lMSI-catchers (Stingrays, DRTboxes, etc.) or other similar technology? Specifically: a. Which components within your department use such devices? If multiple components use such devices, is there department-wide guidance governing their use? b. Since [fiscal year] 2010, how many times has such technology been deployed, and how many phones were identified or tracked by this technology, including devices used by the targets of the operation as well as non-targets whose information was incidentally

swept up? c. In what types of operations are these devices deployed? What statutory authority permits the use of this surveillance technology? e. Do [the Department of Homeland Security] and/or [Department of Justice] obtain a court order prior to using such devices? If so, do DHS and/or DOJ inform the courts of the number of individuals likely to be impacted; the scope of acquisition; or the specific technology being deployed?

Last month, local judges in Washington State started to realize that when local cops come to them asking for permission to conduct a type of phone surveillance, known as a pen register or trap and trace, they will often use a stingray to get the information desired instead. As a result, the Pierce County judges now require police to specifically state whether they will be using a stingray.