Dateline | August 24, 2012
>>> in the years after angie dodge's murder, the man who confessed to taking part in her killing, christopher tapp, was safely tucked away at state prison . his alleged accomplice, ben hobbs, in prison for a different felony, was never charged with angie 's murder. and idaho falls police told angie 's mother carol they still couldn't find that third man, the one who left his dna on angie 's body. that's when carol became, her word, obsessed. if the police couldn't track down her daughter's killer, well, then she would.
>> the anger just surged through me. and that's when i went to the streets and i literally put 60,000 miles on my truck, searching for her killer.
>> reporter: you put yourself in harm's way?
>> oh, absolutely. i remember going to a place and the lady said you need to leave before somebody hurts you.
>> reporter: that's how the days and weeks passed.
>> i had a gun put to my head one night.
>> reporter: in a frenzy of new leads, but never panned out, but carol often ending up parked outside the apartment where angie was murdered.
>> i would just stare at that house and stare at the windows. and try and figure out how scared she must have been.
>> reporter: something else carol couldn't stop doing, reading police reports. practically memorizing them.
>> i don't sleep and i get up and i just go, what part of this don't i understand.
>> reporter: it didn't make sense.
>> none of it made sense.
>> reporter: and in one of those reports, carol found a phrase which the more she read it sounded out of place in the dna world. it was about pubic hairs, which in addition to the semen had been found on angie 's body.
>> it was written in this lab report , that it is similar or same as the victim. and i said to myself, it is either angie 's or it's not angie 's. it can't be an either/or. not in today's society.
>> reporter: then carol remembered reading an article about an internationally known dna expert who just so happened to live and work right in idaho . a field to be a recognized dna expert.
>> it is fun. nobody invited me to talk on television.
>> reporter: this is the expert, dr. greg hampikian, a fruit fly geneticist who now spreads his infectious enthusiasm to students at boise state university . dr. hampikian's work is not all done in the classroom. in fact, his own path changed in 2004 when he was asked to test dna which eventually led to an innocent man being freed from prison in georgia. the doctor and exxoneree wrote a book together, and just like that, the doctor found a new calling. hampikian is now in high demand. in 2011 , he was part of the team credited with freeing amanda knox . that american college student in prison for murder in italy. and in his spare time , hampikian is the founder and director of idaho 's innocence project .
>> it is an unfortunate thing that our name is innocence because honestly, you know, i've worked on, i think, 13 exonerations now, four of the ones in georgia, they found the actual perpetrator. so to those four guys, i'm the guilty project.
>> so now, the coincidence you just couldn't make up, the very week carol left a phone message for dr. hampikian asking for help, idaho 's innocence project had just taken on a new case. the case of the man convicted of killing carol 's daughter, christopher tapp. the doctor called carol back.
>> her words to me, i'll never forget, were i just want to know what happened to my daughter. and, you know, it still brings the hair up on the back of my neck.
>> reporter: curiosity, did it surprise you?
>> the knowledge surprised me. she's turned all of that love and devotion for her daughter into a very careful record of this case.
>> reporter: so she read that report to him, the one that said the pubic hairs found on angie were similar to or the same as the victim.
>> he goes, they're either hers or they're not.
>> reporter: just as you thought.
>> he said, where are the hairs? i said, i assume they're still in evidence.
>> reporter: so she called the idaho falls police department , which found the hairs in an envelope in the evidence room where they had been stored for all those years. after carol 's call, those pubic hairs were sent off to the crime lab where state of the art dna tests could show chris tapp was there at the crime scene or ben hobbs was there at the crime scene or the entirety of the physical evidence was left by one unknown third man. that was a fundamental question, huge, and the answer from the dna left no doubt.
>> one person who did this, in terms of the dna .
>> reporter: one killer. the science said there was no evidence there were three attackers in angie 's apartment that night as the police had theorized, but just one. and that remarkable news could mean only one thing at least according to the idaho innocence project . chris tapp's story was a false confessi confession, he was not there, he was an innocent man. the theory of multiple killers, ridiculous said hampikian.
>> to imagine there is this group of criminals who know about dna and are so careful, what did they do? they planted somebody else's semen and pubic hair and then cleaned up all their own dna .
>> reporter: as you might well imagine, that conclusion that chris tapp had to be innocent, that the killer had never been caught, came down like a hammer to the head on angie 's mother.
>> i was extremely angry. when they have dna , not once, but twice, that belongs to the same person and it is not chris tapp, something's wrong.
>> reporter: so what did you do?
>> i met with the chief. and i asked for copies of all of the videotapes.
>> reporter: those videotapes, the ones in which chris tapp had confessed to taking part in the murder, by most accounts carol knew more about the case than anyone, but the one thing she had never done was watch all the more than 20 hours of the chris tapp interrogation. now, she did. she watched every minute. when she was done, carol dodge was a changed woman, looking at a brand-new case.
>>> coming up --
>> there is times i wanted to put my fist through the tv.
>> the tale of the tapes. what exactly had she found?
>> we're going to go from there.
>> when "dateline" continues. [ female