My parents... when my brother was about 16... started randomly testing his urine for alcohol when he came home at night. (He's 34, a successful engineer who owns his own business now). They were truly at a loss about how to handle the situation. He, I think, was lying about drinking and they were worried he was driving himself home under the influence. He would have to wake them up when he came in but if he'd been drinking he'd find ways to disguise his breath. So... the pee tests.
It was a hard situation all the way around. After awhile he started peeing in a cup BEFORE he went out and then warming it under the water before handing the sample out from the bathroom to them so they'd think he'd just done it. (You can see he's a smart guy).
He forgot one night and so they discovered his trick.
Anyway... I'm not sure why I'm telling you this. Just wanted you to know that it's been done. My brother is fine now. I'm not exactly sure how either of them (parents or brother) feel about the situation in hindsight. I know my brother was very angry with my parents and it may have even spurred him on to drink more... or lie... or whatever. I don't know if my parents think NOW that it was effective. I only know that they were lost and worried. My brother isn't a big talker, especially about feelings. I was away at college at the time so I missed most of it. Just know how distraught my parents were. I see my mom tomorrow... maybe I'll ask her if she regrets that decision or if she would do it the same again.
I really feel for you. My ds is only 2... and of course, I'm hoping to avoid the situation altogether... but I know it happens in even the nicest, most open families. Good luck!
Oh... and as far as what THEY did with the info... they were just doing it as a preventitive measure, thinking that if my brother KNEW he could be tested he'd not take the risk. I think they also used it to judge whether or not he had a serious problem... thinking that if he STILL drank even when he knew he could be caught he must have an addiction. But, like I said... I think the testing may have actually spurred him on. Anyway... if he got caught he was punished... car taken away or whatever.
Good luck again. Please know that lots of kids experiment and it's normal and my brother is fine. BUT that obviously isn't always the case. Some kids get into serious trouble and really need help.