all we had to do with submit the profile to codis -- >> codis? it's >> an fbi computerized systems that come teens millions of profiles that have been collected from crime scenes, from jails, people who have been arrested. >> and anything come back? >> nothing. no hit. >> to larsson, that meant michelle's killer was likely someone about any prior arrest or run-ins with a lot. that meant compute people police police had talked back in the day had to be reconsidered. >> my thinking is, let's start going through this case. let's start finding potential suspects. and the school get their dna and start eliminating them from that partial profile. >> so, now are we back to andy and all those other boyfriends? >> correct. >> nearly 30 years after michelle the's death, everything old was new again. boys with alibis back in 1979, we're now middle aged men with something more valuable than a story to offer. they had there dna.