salvage yard to take photo, some at steven avery's. >> he starts making calls directly to teresa halbach rather than going through autotrader. >> and kratz determined on the day before teresa's visits, avery purchased these shackles and handcuffs. >> when teresa arrived. >> he answered the door that day wearing a small white towel, and teresa we know is creeped out by that behavior. she tells friends and coworkers about that. >> kratz believe that shows signs avery had a sexual obsession with teresa that led to her murder. why would avery do this, on the verge of getting this great windfall, millions of dollars. >> that's a great question. we don't know. we know he is a psychopath. >> do we know that? >> let's say i allege that, okay. i believe that deep down. >> kratz discovered more in avery's past. 18 years before teresa's murder, avery wrote this letter to his estranged wife from prison saying "i will kill you." and a former fiancee told police he had physically abused her. and kratz says he learned something even more disturbing.

. >>> how do you feel that so many people think steven avery is innocent? >> it's emotional.st a nice person. what's happening is wrong. the evidence is beyond overwhelming. steven avery is guilty. >> i'm innocent. >> the story gripped the nation in the series "making a murderer." >> so americans have learned about it. >> it's been heard by people around the world. >> steven avery and his nephew, convicted of murder in the haunted killing of