Hovering above the streets of Minneapolis last week, just days after the death of George Floyd, thousands of protesters could spot an unusual sight.
The unmanned, winged aircraft fitted with a turbine engine and camera circling the city was a Predator drone, operated by the US Customs and Border Protection agency to monitor the crowds in case tensions escalated.
The Predator first gained notoriety in Iraq and Afghanistan, where it was widely used by the US military. These days, however, the use of sophisticated military-grade equipment by police to tackle domestic protests is becoming normalised.
America's riot police and SWAT teams routinely use heavy equipment originally designed for the battlefield. As well as drones, billions of dollars worth of heavy assault rifles and armoured vehicles have made their way into the arsenals of small and medium-sized town police forces through army surplus schemes.
M728 vehicles, which are based on the chassis of a battle tank, are used as battering rams by police in drug raids. Under Department of Defense agreements, some local police forces for towns of just a few thousand people have been beefed up with millions of dollars worth of elaborate kit.
Less visible but just as important, military-grade surveillance technology is also being used to police protests where tensions are already running high.
“This is an excellent example of how protests and protesters have been put under mass surveillance at the moment,” says Ilia Siatitsa, legal officer at advocacy group Privacy International.
“Authorities clearly show that they’re already capable of conducting generalised, invisible real-time surveillance of protesters from a distance without people knowing or consenting.”
As demonstrations threaten to boil over following US President Donald Trump’s call for the National Guard to “dominate" the streets, police are likely to draw on more technologies to quell the anger. What is this likely to mean for the future of the protests?
The use of drones is part of a growing trend by police to adopt advanced, military-style surveillance methods. The particular model used in Minneapolis has previously been used to spy on illegal activity on the US-Mexico border.
But it is not just aircraft being used by officials for surveillance. Down below, police officers are increasingly using body cameras to collect video and audio footage of protests which can also help officers geolocate an incident using GPS data.
The Minneapolis Police Department is currently using technology from a company called Axon for street-level tracking, allowing officers to record video that can be channeled to an app on their phone for replaying.
There have been reports that sophisticated technology developed by Clearview AI has been used in the city to scan crowds. Clearview AI's software can identify people in public spaces with photos scraped from social media.
The company’s software, currently used by roughly 600 law enforcement agencies in the US, is usually used to track down criminals or terrorists through its sophisticated facial recognition tool. Since February, the technology has reportedly been used hundreds of times by the Minneapolis Police Department to identify people.
According to Siatitsa, the use of such technology can have a “chilling effect” on protesting as it can “dissuade” people from attending over fears that authorities will have powers to identify them.
But these are unusual times, with protests taking place in the midst of a global pandemic. That means face masks being worn to shield against coronavirus have forced developers of facial recognition technology to innovate.
Early on in the outbreak in China, reports emerged of cameras that could detect faces hidden by masks. Apple later followed up with an update to its iPhones that allowed people wearing masks to still make use of FaceID to unlock their device.
These technologies, which form part of a wider range of biometric tools, are increasingly becoming a central part of the strategy to control protesters, alarming privacy advocates.
“No longer limited to fingerprints and DNA, publicly known traits such as a person’s face or voice can now be run against the Department of Motor Vehicle, social networks, and other databases to secretly identify and track almost every American,” says the American Civil Liberties Union (ACLU).
It adds the use of such technology “completely undermines” the ability of someone to travel in public or gather with friends anonymously.
Other hardware-based technology is also being used. Phone trackers known as “Stingrays”, which cost around $169,000, can gather the phone numbers of people in a crowded area where protests are taking place by mimicking a network tower.
By requesting the ISM number linked to a protester’s SIM card, authorities can figure out who has attended the demonstration. Stingrays have the ability to track location data as well as intercept information sent from your phone, according to the ACLU.
“Whenever a Stingray is used to locate a phone, it also collects information about hundreds or thousands of other phones and their users,” the union said in a blog post.
“The technology is often used without a warrant, and judges are often kept in the dark about its capabilities and limitations.”
While police forces have become better at identifying protesters, demonstrators too have upped their game in a bid to protect themselves.
Burner phones, switching off face ID and touch ID, and scrubbing photos before they’re posted are part of a range of measures used by protesters. The Electronic Frontier Foundation has even provided a guide for those attending demonstrations.
The detailed advice includes “full-disk encryption”, which will protect the data stored on a mobile phone if it is detained by authorities.
Other advice urges protesters to install the highly-encrypted messaging app Signal, allowing them to communicate away from the prying eyes of the authorities.
There are calls to limit the kind of hardware America's police can gain access to. Under the Presidency of Barack Obama, the 1033 programme, where old US military kit can be bought up by local police forces, was scrapped. But under President Trump, it was reintroduced. Now, some lawmakers are trying to have it repealed once again.
Policing mass protests of this kind is unlikely to ever be easy but the line between protecting people and invading their privacy is a fine one.
“We appreciate the difficulty they're having in trying to ensure the safety of everyone,” Siatitsa says.
“Right now we’ve seen all the security around the confidentiality of information in order to participate in protests being completely evaporated under all this accumulated surveillance technologies.”