Sean Penn -- Chapo's Lawyer Says He's a Liar

Sean Penn lied about his interview with El Chapo, and he might even be called to the stand in the drug lord's trial ... so says one of Chapo's lawyers.

Juan Pablo Badillo is calling BS on Penn's Rolling Stone article, in which he says Chapo boasted he was the world's premiere drug trafficker. Badillo called it "a lie, absurd speculation."

Penn, who grabbed a smoke outside Giorgio Baldi Thursday night, was mum on the claim, but he did sit down with Charlie Rose and open up about the interview, calling it a failure because it put the spotlight on him, not the world's drug problem.

The full interview will air Sunday on "60 Minutes."