As the mother of an addicted adult son, I liked to know the truth but most times I already knew just by his attitude and actions.
My deal with anyone was that I won't seek out anyone to discuss his "condition" but if asked, I will always tell the truth. If that was uncomfortable for me, I would suggest they ask him directly...that was an "answer" too.
We don't have to be the addiction police, we know what we know and don't need proof.
Mother's have good instinct. That's enough.
Good luck dear.