A little over a year ago, FBI documents obtained through a Freedom of Information Act request revealed that the agency used spy planes equipped with cameras and heat-based imaging technology during the Freddie Gray protests in Baltimore. At the time, the FBI reassured the public that it did not use the aircraft to see into homes. In any case, the FBI’s spokesperson Christopher Allen told the Washington Post, the infrared cameras cannot detect “specific heat signatures” through solid objects, like walls.
But in a previously redacted section of this guide, the FBI seems fully aware that heat-sensing technology is capable of peering through solid objects, such as foliage and doors. For that reason, the guide actually advises against flying over private residential communities “if operationally feasible.” Such aerial surveillance of urban centers, like Baltimore, will inevitably turn up heat signatures from within apartment buildings and row homes. According to experts on this technology consulted by The Intercept, those heat signatures would most likely be grow lamps, used for cultivating drugs: A person’s heat signature would likely be indiscernible from other heat sources unless he or she were stationary within an otherwise unheated home.
Infrared cameras offer the FBI the possibility of seeing into spaces otherwise accessible only by intrusion. But if the FBI uses the cameras this way, the guide notes, “it likely constitutes a search subject to the requirements of the Fourth Amendment.” And to the extent that cameras incidentally pick up heat signatures inside people’s homes, “no affirmative investigative use may be made of such information, unless exigent circumstances or other authorization permits its use.” The guide’s authors don’t make explicit what would constitute “exigent circumstances.”
FBI employees can request to use infrared cameras even during an assessment, which is the bureau’s lowest level of investigation and requires no evidence of wrongdoing. In an assessment, the FBI can recruit informants, conduct physical surveillance of a person’s public movements, and surveil from the skies — though likely only for 72 hours, according to the manual.
The 2013 version of the Domestic Investigations and Operations Guide, published on the FBI’s website in the fall, updates the requirements for using the cameras slightly. Now employees must apply for written approval to use the cameras by documenting “the reason and objective” for doing so. Apart from that, the relevant passage is largely redacted or the same as the 2011 version obtained in unredacted form by The Intercept.
Whole missions using cameras permanently attached to surveillance planes “must be recorded,” the 2011 operations guide stipulates, and the records stored in what’s called the “electronic surveillance [ELSUR] subfile.” But while the guide includes instructions for creating and maintaining these investigative files, it says nothing about when to destroy the files once an investigation has concluded.
Forward-looking infrared, or “thermal imaging” cameras, come either as portable units or as cameras pre-mounted on airplanes. The cameras record video while detecting heat signatures. Humans, animals, and other objects, like heat lamps for growing marijuana, all produce detectable signatures.
The technology is useful, the guide’s authors write, when employees have difficulty conducting physical surveillance without being noticed, and when they need to track down “fugitives,” or to conduct “perimeter surveillance,” “search and rescue operations,” or “vehicle pursuits.” At night, the cameras can help the FBI find suspects who are “hiding in bushes or other perimeter areas” waiting to ambush investigators on the ground; or those in open areas like fields or parking lots; or those hidden in the “curtilage of a dwelling,” meaning someone’s yard. The Massachusetts State Police actually used infrared cameras and aerial surveillance to find Boston Marathon bomber Dzhokhar Tsarnaev, who was hiding in a boat while on the lam.
Nathan Wessler, staff attorney at the American Civil Liberties Union, wrote in an email that spying on front and back yards likely invokes more privacy issues than the FBI concedes, as it can reveal “a great deal of private, sensitive information that is otherwise obscured from public view.” It’s not clear whether the yard of a private dwelling qualifies under the law as an “open field” — an area the Supreme Court declared in 1924 unprotected from warrantless police surveillance.
David Nalley of Nalley Private Investigations, who has used infrared technology in private practice as well as in law enforcement, told The Intercept that the cameras are unlikely to pick up on people’s heat signatures inside of homes both because of insulation and because windows reflect heat.
“The infrared (heat) emissions have to pass through to be seen. For instance, when I look out my office window using a thermographic scope, I see a reflection of the heat inside the office, not what is outside,” he explained.
However, drug grow lamps, which emit a great deal of heat, would certainly be visible. Nigel Tolley, a former employee of the infrared company PR-Infrared, described drug raids in which even the best attempts to insulate “hot houses” failed. The house with the grow lamps glows bright white to passing helicopters, while all the other houses are dull gray.
Tolley said that many variables can determine what the cameras can and cannot discern within a home: open windows, thick insulation, other sources of heat. He also noted a “lag” time in detecting differences in temperature.
“So far, I haven’t seen photos or video of people inside a house,” he wrote in an email to The Intercept. “I think that the lag is too long through a proper wall for it to be useful. You could certainly tell which room a person was sleeping in, in an otherwise unheated house. But, is it a person or is it a computer or lamp putting out a dozen watts of heat? It is hard to tell through a thick wall.”