The FBI flew surveillance flights over Baltimore during the unrest that followed the death of Freddie Gray and over Ferguson, Missouri following the death of Michael Brown, using advanced surveillance techniques including infrared cameras, documents obtained by the American Civil Liberties Union (ACLU) have revealed.



The internal documents from the FBI and the Federal Aviation Authority (FAA) show that one Cessna aircraft circling over the Baltimore protests – which was registered to an FBI shell company named “NG Research” – carried an infrared camera mount as well as an FLIR Talon multi-sensor camera system, which includes thermal imaging technology and laser illumination.



Nate Wessler, a staff attorney at the ACLU’s Speech, Privacy and Technology project, told the Guardian that while the supreme court had upheld the use by agencies of surveillance planes, it had not considered their use in light of the high level of sophistication of the equipment now on board.



“That’s what really raises part of the concern here,” he said. “We know at least one of these planes was equipped with infrared cameras – we don’t know how powerful [they are], but if it is used to gain info about the interior of homes, then a warrant is clearly required under supreme court precedent.”

FBI director James Comey confirmed to Congress last week that surveillance flights had taken place over Ferguson and Baltimore during the protests. The capabilities of the aircraft involved was not revealed.



In June, the Associated Press reported that the FBI maintained a fleet of at least 50 aircraft flying such surveillance missions over cities across the US. At the time, the FBI claimed the planes were not equipped for mass surveillance.

However, the documents obtained by the ACLU, which were obtained following requests under the Freedom of Information Act, show the agency is holding on to all surveillance tapes collected during the unrest in Baltimore and Ferguson.



Parts of the documents which would identify more of the electronic surveillance equipment used are redacted, meaning that the full extent of the capabilities of the aircraft is still not fully known.

The ACLU said on its website that this “suggests that those flights were perhaps using more sensitive or powerful recording gear … though what kind we don’t know”.



Wessler said that while there was no information on whether the data had been used to bring charges against protesters, “if they are storing that footage they are leaving open the possibility that it could be used for evidence later on”.



He continued: “There may well be information in the footage that sheds light on illegal activity, but also video of protesters exercising their first amendment rights, and residents of Baltimore going about their daily business, which is why it is so important that there are robust privacy rules in place ahead of time and that the public have access to the content of those rules.”