Dateline | August 24, 2012
>>> more than a dozen years after her daughter's murder, the feet was quaking. new dna tests revealed that none all they kept saying is he confessed, carol . he confessed.
>> reporter: but, was it a real confession? carol asked for and got a complete set of tapp's videotaped confessions and what she saw amazed her. by this time, she knew so much more than she knew before, knew, for example, that then detective jared fuhriman who ran the interviews, had been a school resource officer, well known to the young chris tapp.
>> i trust you and hopefully you trust me, okay?
>> fuhriman kept telling chris , just trust me, chris , you got to trust me. we go way back, chris . and i think he was taught to respect adults and he was a follower.
>> reporter: she watched as chris insisted he knew nothing and then she saw detectives as they're trained to do, subtly make tapp an active participant.
>> hypothetically, chris , you were there, okay?
>> hypothetically, chris , how do you think it happened? and i remember chris saying, you mean, like a tv show ?
>> reporter: next she saw police administering polygraph after polygraph and almost always with the same result, they would tell him he was deceptive. and how when tapp was promised immunity, his story about ben hobbs changed.
>> got a knife and just started to cut her.
>> reporter: but perhaps what troubled carol most was seeing how confused tapp was, even ten days after his first interviews, he still seemed not to know what house angie lived in.
>> and she lived on a corner.
>> reporter: police, carol noticed, kept correcting him. for a guy who had taken pride in a murder, tapp also seemed to not know much about the layout of angie's apartment.
>> sometimes it helps to dr s ts to draw it out.
>> reporter: when they asked him to draw it, he couldn't do it. detectives even perhaps inadvertently showed him where the murder occurred.
>> here in the bedroom, back here.
>> reporter: oh, yes, and there was more. police had always told carol that chris knew things only the killer would know, the clothes she was wearing. now, carol could see for herself on tape the reason chris would know those things. carol was stunned to see police had shown tapp photos of the crime scene .
>> that's how you remember it? that's how you don't remember it? if it jogs your memory for you.
>> there is times i wanted to put my fist through the tv.
>> reporter: and finally, remember that the police theory of the crime after dna didn't match tapp or hobbs was of three people committed the murder together. the detectives spent hours literally trying to drag the name of that third man out of tapp. and when carol saw the tape, well, you watch it.
>> the name doesn't come to my head.
>> i think jeff.
>> first name.
>> reporter: by the time you had gone through all the tapes, what did you think about chris tapp, the man you believed all those years --
>> how did they do this to me? how have they managed to keep someone in prison for all these years and it is a possibility it is not there.
>> reporter: after that eureka moment, carol dodge made a decision, she would do more than search to find her daughter's killer. she would actively work to free christopher tapp, the only man convicted of the murder.
>> i think that chris truly got taken seriously after i made my contact with boise state .
>> she was the first victim's family member who came forward to work with the innocence project on a case. i mean, she's the leading edge of a group of people in who have come forward and said, you know what, we just want to know what happened.
>> reporter: but no matter who was now on his side, chris tapp was face to face with two very uncomfortable truths. one, years of appeals had done nothing to overturn his conviction and prison sentence , and, two, the detective who put him behind bars had gone on to a much more powerful position in idaho falls . and he was still absolutely certain that chris tapp is as guilty as sin.
>>> when we come back, the former detective reveals what makes him so sure of tapp's guilt.
>> he took us into the bedroom, and relived that night. and you could see it on his face, he was reliving it.
>> when "the confession" continues.