Domestic Investigations and Operations Guide
Bureau Hid Doubts About Reliability of Stingray Evidence Behind Redaction Marks
Jan. 31 2017

Stingrays are devices, about the size of a briefcase, that trick nearby cellphones into connecting like they would to a radio tower operated by a telecommunications company. Instead of providing service like a normal tower, the device jams signals in the area and records information streaming from hijacked phones — information such as geolocation data, phone logs, and possibly even recordings of calls. Stingrays are popular with law enforcement and are manufactured by the Florida-based Harris Corporation. Other companies make functionally similar products that are referred to using the generic term “cell-site simulator.” This internal FBI manual furnishes one of the very few available national policy guides for using the technology.

The FBI believes that Stingrays are very challenging to operate effectively — so much so that the bureau discourages the use of evidence obtained through them in court. Here the FBI instead recommends using other evidence that will “corroborate and verify” findings from Stingrays. The Stingray guidance raises new concerns about a technology the bureau was previously believed to be keeping out of court due to a desire for secrecy, not over reliability concerns as well.

“The FBI is sending this sophisticated surveillance technology out into the field to be operated by people who don’t know how to use it … technology that by its very nature interferes with and tracks innocent people,” said Chris Soghoian, chief technologist at the American Civil Liberties Union, after reviewing the guidance.

1 Agents warned not to use Stingrays for evidence

The guide recommends that FBI agents steer clear of “using the results” of surveilling people with Stingrays as actual evidence in court. That is at least partially because the technology is difficult to master, and so the FBI lacks confidence in the evidence it produces.

The manual recommends finding other information to bring to court to confirm what is known from a Stingray: say, pre-recorded calls between a victim and a suspect supervised by law enforcement, or information obtained by the FBI’s elite Mobile Surveillance Teams.

The technique of swapping evidence this way is known as parallel construction and can be used to deny plaintiffs the chance to challenge the constitutionality or accuracy of the original evidence obtained against them. Parallel construction allows law enforcement to point to the second evidentiary chain and claim it as primary — arguing that a case does not rest on evidence acquired through, say, a worryingly unreliable technology, like a Stingray.

Many activists consider parallel construction an open secret that’s hard to prove in practice. “We of course knew this was happening, but I don’t know that there’s any official FBI guidance that’s public,” Andrew Crocker, staff attorney at the Electronic Frontier Foundation, wrote in an email after reviewing portions of the manual.

- Jan. 31 2017
2 Privacy concerns around private homes

The guide acknowledges that intentionally using a Stingray device to gather information within a private residence likely triggers the Fourth Amendment and requires a warrant. But depending on the range of the tracker — Stingrays vary in range depending on their model and settings — cops are likely tracking phones in private homes all the time unintentionally.

“Unless the FBI is in a public space with no surrounding apartment buildings, lofts, houses, et cetera, the Stingray is going to reach phones that are in someone’s home — even if the phones in those spaces are not the phones that are the target of the search,” points out Jennifer Lynch, senior staff attorney for the Electronic Frontier Foundation.

- Jan. 31 2017
3 Jamming signals for everyone

The guide acknowledges that Stingrays and cell-site simulators jam phone signals in order to function. But the passage appears to minimize the extent of that disruption, comparing it to a quick dropped call or loss in service for the target’s phone. While they go about collecting information from their targets, Stingrays can reportedly interrupt cellphone service for entire neighborhoods, drain cellphone batteries, and, more dangerously, block 911 calls.

The guide suggests that the rules everyone else has to play by — such as not interfering with commercial cellular frequencies — “arguably” don’t apply to the government because it isn’t a “person.” Moreover, the FBI has maintained in court that Stingrays are an inconvenience only to their targets. The ACLU’s Soghoian finds this line of argument problematic: “All the evidence we’ve heard is that the impact is on the community, not just on the individual.”

- Jan. 31 2017