so our number one suspect was carla's boyfriend, rodney mccoy. the reason being is that most murders are going to have somebody that knows the person involved. stranger killings just don't happen that often. so when you have a killing of a woman, a lot of times, it's a husband, boyfriend, somebody where there's a passionate. just by the nature of the crime, we had to keep looking at rodney until he could be excluded. josh mankiewicz (voiceover): that wasn't the only reason. as they dug through the file from the early days of the investigation, detectives found three letters sent to police. leah wagner: one of them was postmarked the 25th of february in 1974, so just a few days after carla was found. josh mankiewicz (voiceover): all three accused rodney of murdering carla. josh mankiewicz: this could be the killer trying to point the finger at rodney to get suspicion off him. that's correct. mm-hmm. or it could have been a witness that knew it was rodney. josh mankiewicz (voiceover): there was no proof offered in any of those letters. so detective