i mean, the guy is -- the evidence whisperer. another nickname for him is st. larry. >> reporter: larry sees things other people don't see? >> larry sees things that many people don't see, yeah. and he looks at it from a different perspective. >> reporter: they both felt the key to the case lay in sam lopez's own words, his taped interviews with the original detectives. and they thought the perfect man to listen to those interviews was the evidence whisperer. guilty people have tells, just like in a poker game? >> absolutely. they don't have that innocent mindset, and they -- they have other fears. they fear being caught. they can't get their stories straight because there's too many details. >> reporter: montgomery spent months carefully listening and re-listening, watching and re-watching, hours of sam's interviews. looking for the tells. >> how long have you guys been dating? >> it's -- it's an off-and-on thing. on-and-off thing. >> okay. >> reporter: tell number one, how sam talked about his relationship with cathy. >> see, i was going out with