MARQUETTE, Mich. — Attorneys for a couple accused of plotting to extort $680,000 from John Stamos are trying to get them off the hook by attacking the actor’s character and the FBI’s credibility.

Defense lawyers in the trial of Allison Coss and Scott Sippola have portrayed Stamos as a promiscuous drug user — allegations he denied while testifying Tuesday. They’ve also asked federal agents whether they destroyed evidence after setting up a sting operation to snare the defendants, drawing emphatic denials.