While a disputed video might not considered sufficient evidence for conviction, it would most definitely constitute probable cause to justify forensics of the i

While a disputed video might not considered sufficient evidence for conviction, it would most definitely constitute probable cause to justify forensics of the involved defendant's devices and for a subpoena to Facebook for the deleted data (which, in many cases, is not really deleted-deleted and may be found on e.g. backups) - and those things generally would be sufficient to verify if the video is real or altered.