are is one thing, knowing who they are dealing with is another.
knowing that they are probably going to lie to you about both is a reality that some parents fail to grasp.
taking a look into juniors room every so often might just turn up a few 'gems' about the life he is living. look for the cigarettes, the drugs, the weapons, and the other things that you don't want in your house.
this lets him know that you believe in "trust but verify". if you don't let him know you do it, you will have a much better success rate.