1) The cop tripped you up. By saying 'no comment', you could've walked away from this at the outset. He's feeling pretty pleased with himself. He has the upper hand. And he thinks you're dumb. Nothing boosts the self satisfaction of a cop like exposing someone for being a 'dumb crook'. That he relished the chance to do you slowly, in front of your parents, speaks volumes.
2) When you laugh off the words of the all powerful, righteous, caution giving policeman (or are indifferent to his 'gateway drug' claims), the thin blue line between you and a life spent making beaded necklaces and engaging in such hideous pass times as not glassing people at the pub, in front of adults (you are not his peer, your parents are) you throw a quantity of powdered napthalene onto an already intense flame, because he 'has more expertise' than you as he sees it. He has seen lives destroyed first hand, and of course, it all starts with weed... You aroused contempt in the cop heart, a rookie mistake, as the late, great Hunter S Thompson will tell you.
3) In the cop's eyes, its highly, highly improbable that, being a 17 year old caught with a piece of relatively sophisticated paraphenalia (think about it - how many dudes at 17 you think this guy grabs for possess cannabis? Most are smoking out of a springer, a small pipe or rolling shitty joints, right?) this was your first outing with a little Mary Jane. Clearly, you vile juvenile delinquent you, you have been abusing this heinous drug for such a length of time as to have developed the taste for the finer means of consuming it. You are inveterate user.
As to dealing with your folks... take it on the chin. What's done is done. You can no more undo the situation with them than you can dig up a corpse, put it in front of a piano and expect it to offer you a rendition of Elton John's 'Candle in the Wind'. The only way to do this is put on the hang dog expression, explain how you sought to minimise the health risks by consuming it via a non smoking method, act as contrite as possible, and accept that some parents, like police, are self righteous toss troughs when given the chance to work out on you. Your parents have probably been shocked as fuck by having 5-0 in their house, putting on the jazz concerto of Grade A horse shit the caution giver no doubt fed them, in full uniform, saying how your attitude sucked. Dude, if your parents are even HALF intelligent, the anger will fade... Simply, this, too, shall pass.
Re careers and police records - if you aren't joining the cops any time soon, noone will ever be able to see the caution but the police, who will factor it in should you get pinged again, strictly from a 'how to proceed' stand point. If you attempt to join the legal profession in four to five years time, you'll declare it and they'll either let it drop or ask fror more information. If you attempt to join an intelligence agency or apply for other 'protected' positions, it'll come up but will be viewed in totality against the rest of your life.
You were 17. Bottom line - 17 year olds fuck up. But 100% of the private sector will never know about it unless you tell them, and 99% of the other jobs you will do won't be able to see it either. Simple as that.
