How about this: Every recording device sends a stream of hashes to be cryptographically timestamped in realtime as they record. Now the time window to create f

How about this: Every recording device sends a stream of hashes to be cryptographically timestamped in realtime as they record. Now the time window to create fake evidence becomes incredibly small. You have to arrange the fake to be created at the same time or earlier than you will claim that the event happened. You have to know what you need to fake in advance, too, which isn't the case for all fraud. Evidence will be corroborated from multiple places. If I'm in a public place, I can bet the scene is being recorded from multiple places, and I will not be able to predict who will be in that place in advance. Fake evidence can be caught out by finding discrepancies. If the majority of recording device owners whose evidence corroborates can be trusted, then the identification of the fake one can be made with reasonable certainty.