Darnella Frazier changed the course of history by tapping record on her smartphone. We can learn a lot from her about what to do when facing down badges, guns and a potentially dangerous situation.

On the way to the convenience store last May, Frazier came upon George Floyd being arrested by police officer Derek Chauvin. Then 17, Frazier recorded for 10 minutes and nine seconds, during which Floyd was murdered.

She kept a distance so her phone was not confiscated.

She used a steady hand.

And she posted her video on Facebook so the world could see the raw evidence.

“It was a master class,” says Allissa Richardson, a journalism professor at the University of Southern California and the author of “Bearing Witness While Black.” “She played an outsized role in the guilty verdict for Chauvin.”

Cameras are transforming the conversation about police violence, but they’re not all equally effective. Officer-worn body cameras have become increasingly common in the United States, yet they can both illuminate and obscure the truth. Smartphones now allow citizens to film and even live-stream their own police encounters, yet the act of recording can put people at risk in highly charged situations. Many Black Americans are tired of having to document each time a police officer kills a Black person to prove it happened. And while the surge in smartphone evidence has fueled calls for reform, one reason Frazier’s video stands out is because it was so rare in actually leading to the conviction of an officer.

So how can and should you use your phone to bear witness? I spoke with lawyers, police, activists, photojournalists and technologists to get their advice on how to best record the police, both legally and technologically.

What you need to know about filming the police. (The Washington Post)

“The smartphone has become the eyes of our nation,” says Charmine Davis, a Black psychotherapist and mother in Los Angeles. She made an app called Just Us that allows people stopped by police to instantly start live-streaming while letting trusted contacts know about their whereabouts. The idea, she says, is to help people remain calm during encounters because they know their loved ones have been alerted.

The American Civil Liberties Union, too, offers an app called Mobile Justice that offers guidance specific to many states and allows you to share video recordings with the organization’s lawyers.

“Knowing your rights is a different thing from knowing how to keep yourself fully safe,” says Daniel Kahn Gillmor, senior staff technologist with the ACLU’s Speech, Privacy and Technology Project.

Choices you make in the moment about how to use your phone could shape the outcome of the encounter. The experts largely agreed that Frazier’s video was so effective because it told Floyd’s story, rather than becoming a part of it.

Here are five things you should know about how to most effectively — and safely — bear witness with your smartphone.

1. You have the right to film police

Recording officers performing their duties is generally lawful, though details about the circumstances can vary from state to state. Most police departments have a policy on this. Police officers, who may be wearing body cameras themselves, should be neutral to why you are recording and may even be glad to have more proof of how everyone acted.

But you may put yourself at risk of arrest or having your phone seized if you encounter an officer who isn’t aware of your rights … or doesn’t care.

“A good rule of thumb is if you have a legal right to be present — such as on a public sidewalk or even on private property where you have permission of the owner — then you can be there with your camera,” says Mickey Osterreicher, the general counsel for the National Press Photographers Association, who runs training programs for both journalists and police.

Know there are some limits. You can’t disrupt police doing their jobs. “The time, place and manner are important,” says Mike Parker, a retired Los Angeles County Sheriff’s Office commander who now trains police. If you cross yellow tape, or get so close that you are putting law enforcement or yourself in danger, an officer can ask you to step back.

How far back is a matter of interpretation. If an officer tells you to scram, “you can say, ‘It is my understanding I have every right to record this. If you would like to direct me where to stand, I will move,’ ” Osterreicher says. But in general, police cannot legally tell you to stop recording entirely or destroy what you’ve saved.

Practically speaking, the best way to keep from having an officer try to shut you down as a witness is just to maintain your distance, like Frazier did during the Floyd arrest. She used the zoom function on her phone, and her microphone was still able to pick up Floyd’s pleas that he couldn’t breathe.

2. Do it in an obvious way

Don’t try to record covertly or hide away your camera, experts say.

There’s some evidence that being clear you’re filming can actually help de-escalate a situation, which should be everyone’s goal.

Being sneaky could run afoul of local laws, or put you in danger if officers misinterpret your moves. In a tense situation, police are going to be concerned for their own safety — and it’s possible they could mistake your phone for a gun. “The more citizens make officers feel uncomfortable, the more likely the situation will become unstable,” says attorney and police practices and procedures consultant Eric Daigle.

In the Floyd arrest, other cameras showed Frazier was holding her smartphone out in front of her body. “She had it very high and obvious so that the officers would know that she wasn’t doing anything to threaten their safety,” Richardson says. You can even see Chauvin looking directly into the camera.

Police may be particularly concerned about the location and visibility of your hands. That’s why some of the more advanced tools, including the Just Us app, can activate recording simply with a voice command.

There’s even an iPhone Siri voice shortcut — “I’m getting pulled over” — that can activate your phone’s camera without you touching it. (You can download it here, but will need to adjust your Siri Shortcut settings to install it.)

3. Record like a journalist

When you’re a witness, your job is to be a tripod. The more your video looks like a true audiovisual version of what happened, the more useful it will be as evidence.

Many professional journalists recommend filming horizontally because it captures more of what’s happening on the ground (and looks better on TVs). But if you do capture vertical video, which is common in social media apps, try to fill up the frame with the important action like Frazier did. Hold as still as possible, and if you have to move, try to do so very slowly like you’re making a movie.

The more you film, the better. Part of the power of Frazier’s video is that it went on for so long.

When it comes to picking which app to use to record, the best bet is the one that you’re comfortable operating even in a stressful situation.

It can be very difficult to remain silent while something terrible is happening in front of you, but it can also be useful to think of yourself more as a detached observer than an advocate.

“When you look at successful citizen recordings, what do they have in common? They didn’t interfere,” Parker says. “I have seen so many videos that otherwise would have been quite compelling but the video became about the argument between the officer and the citizen.”

4. Lock down your phone

If you film evidence of a crime, the police can ask you for a copy of it. In certain circumstances, an officer might even temporarily seize your phone and get a search warrant to go through it.

In a worst-case scenario, Osterreicher says, officers could try to delete your video. They don’t have a right to do that because of the First Amendment — not to mention ethical policing standards — but some digital security steps you take in advance could help protect your footage.

First, modern iPhones and Android phones offer encryption, but the locks only work if you’ve got a passcode set up. A secure one has more than four numbers in it. And since your face or fingerprint could be used to unlock the phone, you might consider turning off those functions if you know you’re heading toward a protest or another potentially tense situation, the ACLU’s Gillmor says.

There are also ways to make a copy of what you film online in case your phone gets taken or lost. The simplest is cloud backup: If you turn on a service such as iCloud Photos or Google Photos, smartphones can automatically upload a copy of whatever you film (though it may wait until you’re in the range of WiFi for a large file).

Streaming apps such as Facebook, which has a live function, both instantly broadcast what you record and keep a copy of it for later. “Just remember, if you do that then you don’t have control over the footage going forward,” Gillmor says. First, someone who sees it can copy it. And second, if you decide to later delete or hide your video, police could push any Internet company that had access to it for a copy.

5. Think before you share

What helped Frazier’s video reignite a worldwide reckoning on race is that she posted it on Facebook. It provided a completely different version of what had happened to Floyd than what the Minneapolis police initially reported.

But before you post, the experts suggest thinking through how you — and the person you’re trying to help — can stay in control of the narrative.

For starters, Facebook is notoriously inconsistent about what content it allows to stay up or yanks for violating its content standards.

And if you’re not a lawyer, you may not be able to see how your video could be used to build a case against the person you were trying to help.

“I would try to get in touch with the family first,” Richardson says. Survivors, lawyers or a community organization will have a read of the big picture and when and how it makes sense to release the video — just like police already do in deciding when and how to release body-cam footage.

It’s also about respect for the privacy of the people involved. For survivors, video of someone being hurt or killed can be traumatizing. The family might be thankful for having the video to use in court, but not want it on the open Internet as the final memory of a loved one.

“Allow them to remain in control of the humanity of that person’s final moments,” Richardson says.