talkative

Hello Everyone -
I am not sure if i am posting this in a the right section, please let me know if I am not. This is regarding my very dear friend who works at a gas station part time and goes to college. On Thursday he got a ticket on selling beer to a minor - he is a shift in charge in the store and he was busy closing the registers and changing the shift. The store was very busy that night as it was Memorial day weekend and then in all this the cops sent a kid to buy some beer. My friend said that the kid was very tall and looked over the age to buy beer, unfortunately, he was not. The cop gave my friend a ticket and told him to appear in the court. This is the first time he got a ticket in his life in USA, he is a very nice person and I feel really sad that this happened with him. On the ticket it says that the charge is criminal - he will be eligible to apply for his US citizenship later this year, how would that effect his application and what should he do? His owner said that he will talk to a criminal lawyer to see what this is all about. They both have received this kind of ticket for the first time.
Any advice in this matter will be appreciated - thanks!