The camera is always on standby. When an officer clicks the record button, the camera recaptures the fifteen seconds of video before the button was pressed. So an officer can witness an incident - then press the button - and the incident will be recorded.
Surveillance experts say remembering to take that step will be the biggest issue.
"Pushing the button is definitely the key," said Bryan Lagarde, executive director of Project Nola.
Lagarde says there's a risk the police officer will appear guilty of making bad decisions if he or she doesn't press record in time.
"Why didn't he push the button? Well, in reality, it could be because the officer's adrenaline was pumping, they're trying to protect their life, somebody else's life. They're not always going to get to push the button. They're not always going to remember to push the button. If somebody is shooting at them, the last thing they're going to think about is pushing a little button on their glasses," said Lagarde.
Serpas said the city budgeted $295,000 a year to operate and maintain 420 units.
Lagarde said a more expensive version of the cameras could record continuously, and in other cities, the have proven to help officers fight frivolous lawsuits when people make false claims against them.
They also catch when officers do make wrong decisions.
Last year, it's was an officer's choice to wear a pin camera when he or she captured the day Wendall Allen was shot and killed by officer Josh Colclough.
"It's an unbiased witness," Serpas said. "It says exactly what happened. So the emphasis is for them to wear it, and they have safeguards in case they don't."
Serpas said officers will load the video footage into an evidence storage database called the "e-cloud." He said they won't be able to edit the video, but they can add written notes.