problems in the past with boyfriends. >> reporter: then there was the second interview the day cathy's body was found. detective wyatt studied that tape, too. >> there was one thing that was important that sam didn't display, that you would expect to see in a case like this. >> which is? >> emotion. >> he showed more emotion over the contents of the coke can. he picked it up when they left the room. and he's reading the coke can and ingredients and the number of calories. and then at one point, he puts that down and he picks up a baseball hat that he had been wearing and he sees some dirt on it and he brushes it off and he starts swearing about the fact that there's dirt on his hat. >> oh [ bleep ] >> but he never shows any emotion about the fact that his gal has been brutally murdered. no emotion whatsoever. >> and that's a big red flag. >> it's huge. >> reporter: daron went deeper into sam and cathy's relationship. >> there were a lot of things that brought them together. they had dated in high school, they lived across the street. cathy's older sister was married to sam's older brother.