"Residue" only has legal implications. It says nothing about whether he has a problem or not.
People can often get into bad situations out of stupidity rather than addiction or other reasons. I once went out of my way to be a 'good Samaritan' to someone in trouble and set myself up for a felony conviction for dealing crack. A Navy serviceman on leave was involved in a car wreck in rural Garrett County, MD, and I offered to help him. One thing led to another and I ended up selling crack cocaine (as the driver) in the 'hood 70 miles from home in the next state. I don't do illegal drugs, I didn't drink back then, had never even seen crack, yet out of concern for others and stupidity, I allowed myself to become vulnerable to being arrested for selling crack cocaine. Stupid happens.