for one thing, krats tells "dateline" he believes steven avery had set his sights on teresa halbach in weeks leading up to her murder. >> as we move closer to october 31st, we see steven's behavior changing. >> as krats got auto trader's record, he learned teresa had made five earlier visits to the age yard to take photos, some at steven avery's request. >> hetarts making calls directly to teresa halbach. >> and krats determined on the day before one of these visits, avery purchased these shackles and handcuffs. >> when teresa arrives -- >> he answers the door wearing a small white towel. and teresa, we know is creeped out by that behavior. she tells friends and co-workers about that. >> krats believes avery's behavior shows signs of a sexual obsession with teresa that led to murder. >> why would steeven avery do this when he was on the verge of getting this big windfall, potentially millions of dollars? >> that's a great question. you know, i don't know. we know he's a psychopath. we know that he has -- >> do we know that? >> well, i -- let's say, i allege that. i believe that, deep d