hi rose, I just now noticed your comment about him saying they are for his Brother.
That's the best he could come up with.
As for being able to tell if he is an addict, well if that is the norm, perhaps there is no way to tell. If he's not high as a kite, how would you know. He may just be taking enough to maintain his addiction.
Drug testing is the only true proof - perhaps a hair test etc. If he is serious about backing up his story. But yes, regardless he is buying illegal drugs.