Well, I have girls and they cry and tell everything -- but my point is that he needs to learn how to deal with things like this on his own, and I would feel the same way about an 18 year old girl. If a parent interferes it just becomes another, "See, I told you if you did that you would get in trouble" speech they've heard a thousand times.
In real life, sometimes you get caught and you get a warning and sometimes you get caught and you get a ticket. If you get a warning you got lucky and hopefully it should teach you to be more careful next time. That's a real world life lesson an 18 year old needs to experience. I just don't see how having mom get involved adds anything. There are plenty of things high school kids do and get away with - at 18 they need to stop telling their parents everything and learn to cope. What, is he still going to be calling home next year when he's in college to fess up that he slept through class because he was hungover?
I wish you had been my parent growing up