Have him research how to obtain a background check in the state where the incident/charges occurred. Sometimes you can get them straight from the government, sometimes you have to find a company that specializes in background checks.
I have a hard time believing that he doesn't remember where he was or what he was charged with, though. Seems like the kind of thing you'd pay attention to.
Bingo.
On all counts. I remember pretty much every encounter I have ever had with the system. What when and where and yes I was at one point in my life not so reliable.