with the interrogation over, krebs brings investigators to the crime scene keeping his promise to larry hobson. >> he liked larry. it's a weird relationship, but it's a relationship. >> despite that relationship, hobson testifies at krebs' 2001 trial persuading the jury to send him to death row for raping and killing the students. >> from san quentin, krebs writes christmas cards to hobson. grateful for the way he questioned him with decency and kindness. >> it just showed he respected me for the job i had to do. it's just business. >>> coming up, what's it like to be 12 years old and sitting in the interrogation chair? >> i didn't do do it. i didn't do kill my sister. i wouldn't kill her. >>> camden, arkansas. august 2006. >> okay. you know i didn't do it. so who did it? >> thomas cogdell begins talking to himself. alone in an interrogation room. after police tell him he's responsible for the murder of his 11-year-old sister. kaylee. >> i didn't do do it. i'm going to tell them the truth. kaylee's dead. >> unlike rex krebs, thomas is a complete stranger to the criminal justice system. >> here