The hardest to catch are the slight of hand employees that can take money from the safe while it looking like they put all the money in. This is even with cameras watching the safe.

I've read about this in Vegas, where there are people who can palm the the chips so quickly that they weren't able to discern it on 30fps cameras (they had upgraded to 120fps, I think). Didn't know if it was the sort of bullshit people like that like to tell stories about without any evidence or not.