Even if they didn't "erase it", it is obvious that they took no steps to preserve evidence which they justified seizing. Somebody needs to explain how their police procedures permit this incompetence.
Have they no policy concerning the preservation of video evidence seized from defendants? They certainly can't claim that they seized the camera because possession of a camera is prohibited; the existence of the video is the only "justification" for the seizure.
Preserving evidence.
Good point.