How do you tell if your spouse is doing drugs behind your back?

i just got done doing a drug unit in health class, so i hope i can help you. you can tell if he is because you can smell it on him and his clothes (that would be considered 3rd hand smoke) he might come in late at night with the "high like" feeling. he's run down, he doesn't want to do anything with you. He might tell you too often that "I'm going to hang with the guys tonight" and when you asked him where he has been, he doesn't have a good answer. he might be out about the house too much because he is trying to find a drug dealer. it depends on the the drug too. crystal meth some side effects are when the pick at their face causing open sores. cocaine heroin they are always tired (if he's doing cocaine or heroin) look on his arms, back any place that has skin, and look for needle injections. i hope i could of helped in a way, the best thing to do is just keep a good eye of where he is going.