Yes, video surveillance is used by hashgochos, even the badatz, but that’s not testimony – like you said, it’s establishing knowledge.
What I’m referring to is if we have a video of a person doing an aveirah, it’s not admissible for chiyuvei misa or makos(even if there’s no hasraah, i.e. a talmid chacham or megadef)
That’s because there’s no hagadah, no al pi shnayim. The camera isn’t an “aid”
Nevermind the mipi ksavam – i retract that part.