Alcohol furnished to a minor by a minor in a Oklahoma Convenience Store - Is It A Crime?

Let us pose a serious question here for help please. A friend of mine living in Oklahoma has a son who is 17 that works part time at a local Convience store. Recently the local police checked the store out by having an underaged person try to purchase alcohol. Unfortuantely, my freiend's son had a "sernior moment: and neglected to card this person. And of course, you know the rest. The kid selling the alcohol at the store was doins so, as he had in the past, however, there was no one working at the store at the time this happened that was age 21 or over. My friend's son was issued a ticket for "furnishing alcohol to a minor". The court date is next month, and my friend is concerned rightly so. My question to you is a serious one, who really is at fault and what can a local municipal judge do in this situation. To me, the store is at fault in the first place, but had my friend's son used proper judgement and asked for ID, this would have never happened, but, it did, and it could happen to others.

Serious replies only please and thanks everyone.