Video evidence can be great. That is one of the things that gets me with this video, psycho cop knew he was being filmed and the way he just nonchalantly put his hand in his pocket as he crushed the dude shows how wrong it is. In other cases the video only tells a small portion of the story. Body and other cams are good tools but it my area there was a rash of police cars with open hoods. Cops would claim they were having car problems and police car hoods were opened to obstruct the camera view. Body cams would “fall out of place” at certain times. Sometimes it was legit being knocked out of place during a struggle other times cops would do it on purpose. By stander cams can tell different stories from different angles. So video evidence can have its problems, with surveillance videos it gets even stickier, video that convicted someone was used later to get them off on appeal when closer scrutiny was payed to it and it was found the dude in the video was taller than suspect. No one had compared size prior with measurements from known objects in the video. Then you have creative editing and other abuses of surveillance cams. These issues don’t come into play with the psycho cop, merely saying while video evidence can be good, it has had its issues.