blood spatter inside the car. it was a frenzied attack. the theories were awful. drug drug rings, prostitution rings. the town was going crazy. are going to come across the suspect. it was fascinating how they went about the investigation. we got a call and there s three brothers and we think one is a killer. we ve got a live one here. what do you think? we are ecstatic. he was sitting at a booth by the window. it s hard to enjoy your food when you think you are staring at the killer. hello, welcome to dateline. teenager michelle martinko was blessed with beauty, brains, and compassion. her promising future was cut short when she was savagely murdered. that dreadful night was ice cold and after four decades, so was her case. then, a stunning scientific breakthrough helped detectives whittle down a list of suspects to unmask a killer hiding in plain sight. here is dennis murphy with and to then there were three. it was an act of unspeakable violence. it w
cleared. another setback for the cedar rapids pd. but when matt den linger took over as lead investigator in 2015, he thought dna would solve the crime. so he did another deep dive into a case file built by so many before him. now we re trying to find men listed in these reports that could have possibly had a connection to her or men that would have had a connection to the mall. i thought eventually if we swab enough people, we re going to come across our suspect. reporter: but after more than 125 tests, no one matched the killer s dna. they were out of leads. and then parabonn comes in, what is that. they create an image, an actual like up in the post office photo be on the lookout for this guy? exactly.