You know, I have been thinking, a lot of people have suggested he might have been on drugs and he might have. But being in prison for the last 20 years might have led him to avoid hard drugs. Sixteen is a little young to be a serious heroin addict but not impossible, and he was incarcerated until less than 2 years ago. I'm not so naive as to think he would not have access to drugs in prison but it probably would be very limited. And it seems unlikely that a 36 year old man would take up heroin when he got out, especially after his SIL OD-ing.
I don't think we need to consider if he was high. It just does not matter. He is just a bad, bad guy