Over the past few years, more and more police departments have adopted the use of officer body cams. The devices attach to an officer's uniform and record what the officers do while on duty.
However, there is no uniform law of the land when it comes to the public's right to access the footage from the body cams. Depending on the local jurisdiction, or state, different standards are used for the release of the footage. Some will only allow the footage to be released publicly as part of a criminal or civil trial (as the law requires the disclosure then), while others allow the recordings to be released on YouTube (after private and identifying information is edited out).
Video for the People, Not of the People
The purpose of police body cams is to engender the public's trust. The idea is essentially that officers will be less likely to not follow the rules, and will be more likely to do everything exactly by the book, if there is a video record of all their actions. These cams can also provide evidence of corrupt police practices, at least when the corrupt officers are not selectively recording with their body cams.
The recordings are not just of public civil servants (police officers), but the individuals they encounter are, naturally, caught on camera too. This complicates public disclosure as private individuals have privacy rights, even when they are out in public. Those privacy rights can be violated by allowing the public unfettered access to the footage. A simple example involves a traffic stop. If an officer is not careful when handling a pulled over driver's documents, or the footage is not redacted/edited before it is released publicly, a person's driver's license number, address, height, birth date, and (alleged) weight, could all be captured by a body cam.
Unfortunately, due to the sheer volume of police body cam footage, it would likely be impractical, or a drain on police resources, for all of it to be reviewed. Instead, generally, departments review the footage when necessary to review high profile incidents, arrests that lead to prosecutions, or sometimes when officers need help to remember what happened for their reports. Also, when complaints against officers are made by the public, or other officers, the body cam footage can be reviewed.