In her new book, Bearing Witness While Black, Allissa Richardson, an assistant professor of journalism at the University of Southern California, explores how video footage captured and shared by victims, activists and shocked bystanders has alerted the world to a struggle for justice that has a very long history.

Did technology bring us to this moment?
Since African Americans reached American shores, they’ve been trying to communicate injustices that have been meted out against them using the technology of their day. We have icons like Frederick Douglass, who wrote three autobiographies to bear witness to slavery, and Ida B Wells whose The Red Record kept tally of lynchings in America. That spirit has deep roots. But now the tools helping carry that forward are smartphones and social media. For the very first time, millions of people can see these incidences of police brutality themselves – what happened and who did it – in quick time and without the need for legacy media. It is an amplification we didn’t have in the past and it has created some incredible political power.

What is “black witnessing”?
It is a special kind of gaze: one of defiance, self-defence and self-preservation. We have “surveillance” – police body cameras, dash cameras – that give an official account. Black witnessing says: “I want to tell an accurate story of what happened that may conflict with official reports. I don’t want anybody to lie about this death.”

There are frontline black witnesses, like 17-year-old Darnella Frazier, who filmed George Floyd’s killing, and Diamond Reynolds, who livestreamed Philando Castile’s death on Facebook in 2016. So many people – both African Americans but also other people of colour who know they are just as vulnerable – have put their bodies on the line to record first-hand what happened and make sure there is a counter-narrative. Then, after the frontline witnesses retreat from view, anti-police brutality activists pick up the baton and continue. They develop viral hashtags, livestream footage of protests and connect the dots between all these atrocities historically.

What is it about the George Floyd footage in particular that has led to this racial reckoning we are now seeing?
First, it was straightforward. There’s no one trying to go for a gun or a Taser. He is just lying on the ground with an officer kneeling on his neck. Then there was the pandemic. We were all tuned to the same channels looking for the same information on Covid-19 when it popped up. We weren’t distracted by sports or entertainment. It has forced us to reckon with something we might have otherwise ignored.

While this footage of police killing unarmed black people has been galvanising for the BLM cause, viewing it can also be traumatising.
White people have distance, they can look away. Many black people see themselves or a relative in the body of the person who’s lying on the ground. The chill that goes through us is that it’s so easy to take a life of a black person in America and face little to no repercussion. And that fear can be quite paralysing for some. In the book I talk about a number of activists who’ve taken their lives. And there has been a huge spike in suicides, among, especially, African American men and boys. You have to wonder whether it is because of this mediated violence we see now.

Would it be better if these videos weren’t aired? Or do we have an obligation to watch?
We need them for now, because America is still waking up to the fact that this happens. The footage has counted as the proof that these problems are persistent. But once people know and we have justice, there should be some kind of shadow archive where we place the footage so that the victims can finally be laid to rest. I would like to get to the point where black people are just believed. We shouldn’t need this footage to prove that we didn’t deserve our own demise.

I don’t think black people have an obligation to view them, they already know what’s been going on. But white people who are new to understanding this issue would do well to look at some.

You interview 15 activists in the book, including BLM co-founder Alicia Garza, and you note many are big Twitter users. How did Twitter become their medium of choice?
The rise of Black Twitter has been phenomenal and studies have shown African American internet users use Twitter proportionately more than white users. A lot of the early adoption had to do with black people using their phone as their primary source of internet access. You could participate on Twitter without using up a ton of data and you could also use it with a regular cellphone.

I found many of the activists using Black Twitter to organise remotely and on a massive scale. They use it not only to publicise protests but as a kind of newsroom to vet and assign stories, as a news outlet to circulate their own citizen journalism from the field, and as a way of reaching wider audiences by engaging in agitation until their topics begin to trend. They can also reach big-name black journalists who can amplify their messages.

But tweets can also be used by the authorities for intelligence gathering…
It is really chilling. Some activists have had police call them by their Twitter handles at protests. And this surveillance doesn’t just include monitoring their accounts for location and other data. There is evidence, for example, the Chicago police department employed StingRay surveillance technology to listen in on activists’ conversation in real time at BLM protests.

Police body cameras are becoming increasingly popular. Do they threaten black witnessing?
Body-cams vie to tell the story. But just because someone has a body camera on them doesn’t mean they will turn it on and it doesn’t mean the department will turn the footage over.

Then when you have a first-person perspective – as you do with body-cam footage – the viewer may be more likely to assume it. For example, the jumpy footage has a chaos about it that is more likely to add to a sense that the cop did fear for their life. It is not in favour of the victim. No video tells a complete story, but the vantage point that portrays the most objectivity appears to be that which captures both people in the frame.

How can mainstream media do a better job of displaying these videos of police killings?
When white people die – for example in mass shootings – we don’t put it on television, and we scrub it from the internet. Last moments are respectfully treated. It’s telling that we’re OK with showing black people dying on repeat loop. I would like television news to stop using visualisations of black people being brutalised as B-roll [supplementary news footage]. We need context and we need their names. I would also like to see more disclaimers, because many times the footage is shown without adequate warning. And I would like to see journalists finding the same humanising tidbits they dig up about white victims when they die untimely deaths. It took a long time to find out anything about George Floyd’s life; yet his death was on loop.

How can white people be better viewers?
If you are going to share a video, do so with a link, say to a petition about getting that person’s killers arrested. Or just share the petition without the video. But get active – don’t just be a passive viewer.

• Bearing Witness While Black by Allissa Richardson is published by Oxford University Press (£18.99). To order a copy go to guardianbookshop.com. Free UK p&p over £15