system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do police in America get away with so much unnecessary violence, even with video evidence?
gpt
For good or bad, most jurisdictions in the US give officers the ability to use quite a bit of force if they have a reason to believe that their lives or the lives of bystanders are in immediate danger.

Even if video evidence shows that there was no imminent danger, the officer's testimony that they *believed* themselves to be in danger (possible weapon, verbal threat, etc)can be enough to justify it, according to those rules.  So even if the video shows that a perpetrator didn't have a gun, the cop saying "He reached into his pocket, like he was grabbing a gun" could be enough to protect him, in many cases.

This isn't always a bad thing, but has certainly been the cause of many very unnecessary tragedies in the past few years alone.