How do you know when an addict is lying? Their lips are moving.
Unfortunately, I found this to be true of my now-ex whether he was clean from drugs OR using them. Without a commitment to a true program of recovery, addicts have this tendency to continue with addict behavior even without the drugs.
That's where the term "dry-drunk" originated. When the alcohol is gone, but the alcoholic behavior remains.
Also something to think about, some people are just pathological liars and sociopaths. They just lie. That's what they do. They can't stop.