Reporter: With her daughter's memory of the attack still a black hole and the original detective retiring, she asks for a fresh set of eyes. I was always interested in criminal justice. And then in 1999, my sister was murdered. Lisa Kendrick was gunned down on mother's day, 1999. So that pretty much set off my path to being a homicide detective. Reporter: Detective Jodi Gonterman has been with the Albuquerque police department for 17 years and has a reputation for being relentless. The first moment I met Jodie, she told me, "I'm going to find the person who did this." I kind of have a little OCD. If I have something that needs to be done or finished, I have to complete it. Reporter: And right off the bat, she has an unusual suggestion. Something her department had never tried before. I wasn't so convinced that her loss of memory was due to brain damage. I thought it could have been that she was suppressing the traumatic memories that she had. She said, let's try something new. Reporter: Hypnosis. Meet forensic psychologist Dr. Leon Morris. He hypnotizes some patients to unlock repressed traumatic memories. That was literally the first time you met her. Absolutely. All of my contact with her is on the video. Tell me why you're here today. Let's see. There was an attack about almost six years ago. Brutally beaten on the left side of my head. Do I remember any of that? Simply no. Reporter: You didn't know in the beginning whether or not her memories were recoverable? I knew she had quite a bit of brain damage and I assumed that, you know, a lot of it was gone. But I -- in the interview, she talked about going to college. What was your grade point average? 3.7, 3.5, 3.7. I can't remember. So you did extremely well in college. And I thought, "We, wait a minute. She must have remembered something from her previous education. There's some memory there of some kind." Reporter: After his initial interview, Dr. Morris puts Brittani under hypnosis. This is moment when Brittani begins shaking as she relives the attack. Tell me what's -- what is happening. He's -- he's hurting me. How? With a stick. Or something big. I'm bleeding. Did he say anything? Mm-mm. Not a word? You can feel it almost. Like you're kind of reliving that. Reporter: And you said, "Stop, that hurts. Please." I was like defending myself almost. When I saw it, it was heartbreaking, to know that she relieved it in her mind. After that was done the doctor told me that she's going to probably start remembering now. Reporter: And that's exactly what happened. Detective Gonterman follows up with Brittani over the phone and lo and behold, she remembers even more detail about her attacker. He was a tall guy. From what I remember. I did not see any tattoos on him. Do you remember if his shirt was long or short sleeves? It was short sleeved. I remember those eyes, though. They had to have been brown. Reporter: The first fresh lead in years spurs detective Gonterman to try something else new. Seeking out a cutting-edge DNA test that promises to extract more information than ever from that drop of blood. They would take a DNA profile, and they would give us hair color, eye color, ancestry. And then they do a 3D computer-generated image of what your suspect's going to look like. I was skeptical but it was an encouraging sign to attempt it, to do anything that could build on what we knew was our single piece of DNA evidence. Reporter: While detective Gonterman waits for that computer generated image to come back, she gets a call from Brittani. A name has popped into her head. One she says she can't stop thinking about. She said, "Jodi, I remember the name Justin Hansen." She said, "I remember working at the kiosk at the cottonwood mall, and he would come by and visit me." Reporter: But that's it. No memories specifically linking Justin Hansen to the attack. He is seven years older than Brittani and she says she met him years earlier through a friend. When I was in middle school, I had a best friend named Abby, and she had an older sister named Lauren, and Lauren ended up getting pregnant by him, whenever I went to Abby's house or so, he would be over with Lauren. Reporter: By the time Brittani got to high school, she says her friendship with Abby had soured. But every once in a while, when she was working at the mall, she says she would still see Hansen. Do you remember any of the conversations that you had with Justin? They were just like, "Hey, how's your day? How was school? What are you doing later?" A regular talk you'd have with anybody. I actually didn't think anything of it. There were so many names over the years, you just stop being like, "Could this be the one?" Reporter: But then that DNA generated picture comes back and it's a bombshell. I thought, "Wow, it looks so much like him." She called with the news. And she said, "Oh, my gosh, Diane. You're not going to believe this." His picture matches up. And they indicated a high likelihood that the suspect would have either green or hazel eyes, a fairly unique eye color. Reporter: A unique eye color that just happens to match Justin Hansen's. So at that point Justin Hansen did jump to the top of the list.