the interrogation over, krebs brings investigators to the crime scene, keeping his promise to larry hobsona weird relationship, but it's a relationship. >> despite that relationship, hobson testifies at krebs' 2001 trial persuading the jury to send the killer 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 shows that 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 it. i didn't kill my sister. i wouldn't kill her. we asked people a question, how much money do you think you'll need when you retire? $500,000. maybe half-million. say a million dollars. [ dan ] then we gave each person a ribbon to show how many years that amount might last. ♪ i was trying to like pull it a little further. you know, i was trying to stretch it a little bit more. [ woman ] got me to 70 years old. i'm going to have to rethink this thing. [ man ] i looked around a