Pretty simple to authenticate. The video chat service has the time to the second, and the only other piece of relevant information is the guy's location at the time.
They will try to introduce confusion over the significance of the inter-shot timing. However, I predict there will be zero controversy over the recording's authenticity.
They’re still trying to interpret the motorcycle cop’ s recording from Dealey Plaza and whether it was Trayvon Martin or George Zimmer,an yelling help. It would be easier if the left hadn’t led off with “exactly where he was supposed to be, walking to Grandma’s” and “shot in the back.”