. >> doug a temp employee and joe seager a warehouse worker. >> doug ton gate and joe seager were the> reporter: and dan mockbee. >> of course dan mockbee because he's the husband. >> reporter: a short list of potential suspects for prosecutor linda tally smith. >> i refer tost being like the game of clue because you have a very small group and it's a matter of accounting backwards and excluding people. >> reporter: so that's what faced investigators. in which room? with what weapon? and finally, who? >>> coming up -- the questions begin. where was michelle's husband dan the morning of the murder? >> i was sleeping. what a great alibi, right? >> why did you sleep on the couch and she sleep in the bed? ♪ >> reporter: michelle mockbee's siblings remember her as the big sister who literally couldn't lose. >> she was the contest queen. she won every contest there was for like a two-year run. >> yeah. you name it flat screen tvs, tickets to everything gift cards. >> super bowl parties. >> reporter: lucky. >> she loved it. it made her so happy and made it more happy to share her winnings wi

two men who were the last known to see michelle mockbee alive, one a warehouse worker named joe seagerad seemed unusually unemotional about michelle's death when he was first questioned. >> he was one of the ones that made it to the top of the list. >> joe presents himself as a loner. kind of a dry, dark sense of humor and personality. >> reporter: the other guy at the time clock that morning was doug tongate. doug was a temporary employee a newcomer to thermo fisher and an outsider. >> we started looking into his past. saw that he had a couple felonies and some alcohol issues so we thought, this might be a good guy to look at. >> then there was david dooley, the janitor. he and his wife janet has cleaned at thermo fisher for years. david was one of the two to find michelle's body. >> detective mcvay interviewed him the day of the homicide and really nothing that put him to the forefront of anyone's mind. >>. >> reporter: and last there was ed yus ka he was the supervisor who called 911 after finding michelle. >> the blood is right by her office door. it looks like she never got in her