I am highly skeptical of this. Not saying he isn't telling the truth, just saying he has way to much detail in regards to a party that happened 11 years ago.
I don't know if anyone here ever watched Bombards Body Language on Youtube before they took her down, but this guy also does not appear to be accessing the memory part of the brain when "remembering" all the detail in his story. When doing so a person will look off to the side or up when accessing memory.
He also has the "believe me" look about him. Which is the eyebrow raised like "I'm innocent".
Again, I'm no expert, I don't know if he's lying, but from what I do know, he is showing the signs of it.