Yeah, but who did it? All five of them, one of them, another cop not at the scene but with access to the system? Contractors with system access? It's not enough to be sure that a crime happened. Which isn't to say there shouldn't be an investigation or measures taken to make it harder to happen.
And to be more careful, what's the failure rate on those cameras and how many incidents happen a year where it would look suspicious if all cameras fail? If the numbers are high enough we might just have selection bias.
"can really doubt" doesn't work in court, though. Innocent until proven guilty and all that - if there's no actual evidence of tampering you'd struggle to win a conviction.
And when that black guy that was just gunned down "happened" to have a knife in his pocket when searched there's no doubt that he was only seconds away from using it to attack the police?
