GHB denies being there, but he was seen and there is documented evidence of him being there.
Plus there is that creepy funeral scene where he had the giggles when he mentioned the death of JFK.
https://www.youtube.com/watch?v=ft3eGWZd7LE
He was definitely there which is why I hated the respect given to Poppy when he passed. Even Barbara Bush made a dishonest alibi in handwriting for George so she knew damn well all along.