Please don't judge me, I'm not having a good day. My 15 almost 16yo son had 7 friends over for a NYE sleepover, (I'm overseas so it's early NYD here). They had a swim, played twister, listened to music, sang a bit, had mocktails at the bells then shortly after midnight, i went to bed as I'm a paramedic and was working at 0600 today and told them just to keep the noise down. Cut to 0340 and the one girl present crept into my room, woke me up and told me they needed my help. One of the boys had snuck in a bottle of Jack Daniels and necked 3/4 of it, my son had also drank a few gulps. The boy in question was passed out, had vomited everywhere in his sleep and wet his pants and they were terrified. My son was crying.
I checked his obs and managed to get him to blow into my breathalyser - his bac was 0.160. Three times the drink drive limit here. His obs were stable, and I decided to stay up and monitor him until morning. I didn't want to wake his parents at 0400, and I'm clinically trained to know if he needed further medical assistance.
All the other kids voluntarily blew the breathalyser and came up zero. My son blew 0.012.
My initial reaction was to read the riot act with my son. I told him he had shattered my trust and that I was angry and disappointed with him.
Now comes my dilemma. I know the boy who brought the alcohol doesn't have a good home life. His father is a mean bully who has, in the past, hit him as discipline. I'm completely torn on what to do. I was originally going to drive him home at the earliest reasonable time and tell his parents exactly what he had done and let them deal with him, which is exactly what I would advise someone else to do. My son will certainly be facing consequences for taking part, even though both him and the other kids say they didn't know the boy was bringing alcohol. But I don't want him to get a beating either. I'm now sitting here, called in carers leave to work, still monitoring a snoring drunk teenager, wondering what the fuck I should do. What would you do? Please don't pile on hate. I trusted them implicitly.
Even earlier in the night, I went downstairs to pick up their empty soft drink cans etc, and moved a bag aside. It clunked like it had glass in it, and felt heavy. I came upstairs and said to my husband about it. He said "just ask him!?" I said that I didn't want to be rude and seem mistrustful, so he wandered down and moved the bag, and said "who's is this?" The boy said mine, and DH said what you got in it mate? The boy said it's just glass bottles of water, do you want me to show you? DH said "no, mate, don't be silly I trust you" 
I feel so stupid now, and still don't know what to do. WWYD?