Your son needs a lawyer,he will get probation and maybe some alcohol classes,etc. If he is convicted his record will be sealed or destroyed once he turns 18. Every time your arrested it's serious,this is a not a huge charge. He won't be sentenced to jail. It says on other sites the suspension will be for a year. I'm not sure how his license will be affect b.c he does not have one to lose.
If your son's friend hid he didn't put the blame on him,your son was just unlucky to get caught.It is not like he snitched on him or gave false info about your son,that like walking down an icy hill and getting upset that other guy didn't slip.
It's nervy racking when a loved one gets arrested,hire a lawyer,they take the uncertainty away and give you some idea whats gonna happen.They can give you a plan of attack to get the best outcome for your son. Good luck. A local lawyer is the best person to ask for advice.

