There's footage of Michael Brown at a convenience store before he was shot to death and there are tweets showing the aftermath. In between, there's nothing, other than officer Darren Wilson's memory and conflicting eyewitness accounts.

Who watches the watchmen? For a lot of people, the answer to that is body cameras.

"It's the best available evidence that's neutral," Steve Tuttle, vice president of communications at camera company TASER, told The Wire. "It's just an observer. The truth is the truth."

Because of the events in Ferguson, more than 140,000 people have signed the White House petition in favor of creating the "Mike Brown Law," which would require all police to wear body cameras. The City of Ferguson has also announced it will explore the use of cameras, and major counties have begun considering the option.

But before any of this moves forward, it's important to examine the technology itself. The Wire spoke with three companies designing and making these cameras — Taser, Vievu, and Vidcie — to understand the inner workings of their possibly game-changing accessories.

The Design

The first consideration for all three companies came down to placement — these are wearable tools, after all. Taser's model, the Axon Flex, includes two components: The first, a button for the officer to double click so the camera starts recording, and the second, a lipstick-sized camera which would attach to any headgear or the officer's collar using a secure magnetic mount.

Taser

It's a design meant to protect against error. "The button is raised quite a bit, so you're not searching around for it," Tuttle said. "The double tap is to avoid [being] inadvertently clicked."

Vievu, though, took a different approach. The device has a slider that turns the camera on, and is mounted onto the officer's chest (which Vidcie does as well). "The officers we've talked to don't feel comfortable wearing something on their heads for long periods of time," Steve Lovell, Vievu's president and C.E.O., told The Wire. "The officer is too robotic."

The Footage

Here's where things get tricky. If a camera is left on at all times, the data accumulates rapidly (Oakland's police department, for example, has nearly five years of data, or 190 terabytes of space, Lovell says), and all camera designers work with sophisticated software that would only store what's needed. 

The traditional method, used by Taser and Viveu, is to have the officer turn the device on when recording is necessary (a decision made by individual police departments so far), and turn them off when cleared to do so. 

Vidcie, a smaller company than the other two, is attempting a different technique: Their cameras capture feeds, but instead of recording everything, the cameras would work like "little black boxes," Vidcie C.E.O. Romulus Pereira, told The Wire. The video livestreams to the precinct to officers on duty. This makes the officers wearing the devices walking security cameras in a way, with another watching monitoring what's being filmed. 

"It's a chain of custody that avoids human hands from touching [data] until it gets into a secure hold," Pereira said. 

The Storage

Storage is handled by the cloud, the still-quite-mysterious all-encompassing technology that Taser and Viveu primarily use (Vidcie leaves storage options up to individual departments, but also archives using the cloud). But what makes video taken by police cameras so different from the data you send through social media?

The answer: Access. Taser doesn't incorporate a delete button — "Once it's recorded, it's recorded," Tuttle says — it encrypts every frame before uploading it to Evidence.com, Taser's cloud. However, Taser itself can't see the videos, and the only people allowed to view the footage are verified administrators, usually police chiefs.

It works like a digital evidence room. People must be verified to access a video, and then their viewing is recorded — just as you would to enter evidence rooms in traditional police departments. The log also keeps track of what officers do to the footage, whether they apply tags to it to identify the situation or copy it for their own use. The original video remains saved for a certain number of days determined by the department (typically 30), and the administrator receives a notification before the cloud deletes it.

Same goes for Vievu. People logging into the cloud are credentialed, and all user and file activity is logged. Instead of Evidence.com, the company uses a software called VERIPATROL, which allows departments to establish groups of people to see the video. As with Taser, Vievu has no access to the videos.

The Sell

The last step for these companies, then, is to help police departments move along and use the technology. 

"We're in the 21st century," Tuttle said. "We can do this, and we can do this securely." 

Tuttle went on to name three factors challenging the cameras' widespread use: awareness, change, and budget. The first has changed with Ferguson, as more and more people understand the possibility of capturing all footage of such a shooting. The second involves the difficulty of rewriting rules in law enforcement. As Tuttle notes, Taser's, well, shocking Taser weapons, took decades to reach the majority of police departments and replace the traditional batons. 

The third is the budget, as cameras are expensive, costing upwards of $300 for a single set. While Tuttle says the investment would pay off as police misconduct complaints cost much more to handle, Viveu has begun using a monthly pay policy for departments that cannot order dozens of cameras at once but need them as soon as possible. In other words, the faster police departments catch up to technology, the better.

"Law enforcement is under extreme scrutiny and needs to keep current with the technology out there," he said. "It's a community transparency tool."