reporter: in order for the insanity defense to be successful, the defense will have to convince the injujuryonly that he has a mental illness that caused the hallucinations, they also have to prove he didn't know he was doing anything wrong. that will be tough says this defense attorney. i read that the insanity defense is used in about 1% of criminal cases that go to court. and succeeds in about 1% of those. do you think those -- >> that might be an exaggeration. >> reporter: really? >> yeah. it's very, very rarely used. >> reporter: in this instance, where the defendant has taken the trouble to get a disguise, has fled the scene, doesn't that play into the notion that he realized what he was doing was wrong? >> those are problems. there's no question about it. and often times, that's the circumstance that defeats the insanity defense. >> reporter: one key question pursued over the past couple days in the courtroom, was andrea having an affair with hemi neumann? she took the stand and denied it. >> there was no affair. who kills someone else's husband? >> reporter: a whole series of people,