matt murray thought darren by its investigation of cathy torrez's murder was compelling. try twice before. so, murphy called for help from a detective whose legendary skill with cold cases has earned him of reverential nickname. >> larry montgomery's real deal. the guy's evidence was burned, the other is saint larry. larry see things that many people don't. >> he looks at it from a different perspective. >> they both felt the key to the case lay and sam lopez's own words. his taped interviews with the original detectives. they thought the perfect mantle listen to those interviews was the evidence whisperer. >> guilty people have tells, just like an parker game? >> absolutely. they don't have that in the mindset, they fear. if you're getting caught. they can't get the story straight because there are too many details. >> montgomery spent months carefully listening and be listening. watching and rewatching. hours of sam's interviews, looking for the tells. >> how long have you guys mandating? >> it's off and on. >> okay. >> tell number one, how sam talked about his relation