WARNING: This video contains violent footage.

Video has played a huge role in relationships between citizens and the police over the last 25 years. It has helped hold cops accountable for abuse and also protected them from false allegations.

As the country has noticed the death of several young African-American men at the hands of police, there's been a "sudden and seismic" shift toward police use of body cameras — a way to record most, or all, interactions between residents and police. Vox explains how video recordings can be good for both citizens and cops — but can also raise more questions than they answer, especially when it comes to who's allowed to control the footage.

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