"20/20" exclusive. A simple case of high school love, or was this something else? A story we have been following for six months now. The relationship between two high school girls. We watched Kaitlin... See More
"20/20" exclusive. A simple case of high school love, or was this something else? A story we have been following for six months now. The relationship between two high school girls. We watched Kaitlin hunt as she went to jail and our cameras were the only ones there as she shed that Orange jump suit and start a new life. ABC's Matt Gutman has the exclusive interview. Reporter: It's not your typical Friday night for this teenager. She's not walking out the movies or some party with friends. This is Kaitlyn hunt walking out of jail, just months after walking across the stage at her high school graduation. So why was this teen doing hard time? It all began on Florida's treasure coast, Sebastian river high, home of the sharks. "Can't hide that shark pride," they say. But what was hidden in that teenage shark tank called high school no one is proud of. A sex scandal. Felonious love. The sex scandal. Reporter: Kaitlyn hunt was a senior whose crush turned into a crime. Her love, improbably landed her in lockup here at the Indian river county jail. A criminal relation never crossed my mind once. Reporter: Hunt was honor student, a choir girl. ♪ Reporter: And the teen you see tossed in the air by her fellow cheerleaders here, was also voted "Most school spirit." Possessed of a big heart, ripe for love. We had lunch together. We just started hanging out in school, talking. We had fun together. Reporter: The cheerleader, fell for the athlete. At first, just stealing kisses and then, sex in the school bathroom. I would say we had a really close relationship. We told each other everything. Reporter: Although Kaitlyn was 18 at the time, the person she had sex with was just 14, but it gets more much complicated because this is not a classic Romeo and Juliet story. It's a Juliet and Juliet story. The person 18-year-old Kaitlyn hunt says she loved and had sex with was a 14-year-old girl. She's real funny. She was like that person you could go to if you were having a bad day. She would cheer you up in five minutes. She was just all around, just a good girl. Reporter: Kaitlyn's mother, Kelley, says she knew her daughter was in a same-sex relationship, but didn't realize the other girl was so young. Did you meet the girlfriend? Mm-hmm, yep. Reporter: What did you think of her? She was a sweetheart. I liked her. She was very sweet. Reporter: Did it ever dawn on you that the difference in age might be a dangerous thing? I did not know the girl was 14. I had no idea she was a freshman. She looks older than my daughter. Reporter: Something else she says she did not know, the younger girl ran away from home one night and had a sleep-over with Kaitlyn in her home. Eventually, it was a coach who revealed the relationship to the younger girl's parents. The next day they and their 14-year-old daughter were in the sheriff's office. Their feeling was the relationship was unhealthy and inappropriate. Reporter: Unhealthy and inappropriate. But how do you prove the nature of the relationship was sexual? Crimes against children detective, Jeremy Shephard, with the help of the younger girl, sets a trap to confirm Kaitlyn crossed the line. Tell me how you decided to do this controlled phone call with the victim. That is a procedure that we often use in cases like this, in order to attempt to get the victim to get a confession from the suspect for us. Does that mean anything to you? Obviously, it means something to me. Reporter: This is where sweet love, soured. In the state of Florida, even consensual sex between an 18-year-old and a 14-year-old is against the law. Kaitlyn was arrested. They had her in handcuffs in the driveway. Reporter: Put into a police cruiser, what's going through your mind? I was so shocked. You know, I was scared to death because she was so scared to death. Reporter: In an interrogation room, Kaitlyn is questioned, asked about intimate details most people wouldn't want to discuss with their best friend, much less a police officer. . Would you say the first time you all had sex was before Christmas or after Christmas? After. Okay. Reporter: When we met Kaitlyn at the Indian river county jail, we expected to meet a bubbly teenager, but after two months in lockup, the high-spirited girl was gone. This Kaitlyn appeared stunned, nearly speechless, still a bit bewildered by the whirlwind that landed her here. So, you literally didn't know you we breaking the law? No, I really didn't know. I wouldn't have continued. If I really knew what the laws were, and if I knew what I was getting myself into. Reporter: Authorities charged Kaitlyn with two counts of lewd or lascivious battery. Those are felonies. I don't think that either one of these girls thought that anything that they did was wrong. I understand that Kaitlyn is 18. You know, I'm well aware that she's 18, but in no way, shape, or form is that child an adult. Reporter: After her arrest Kaitlyn was released on bail. The judge set a condition. She could not contact her young girlfriend. But the peppy cheerleader and choir girl who dreamed of studying nursing, was now facing a severe penalty for her forbidden romance. A criminal record, sex-offender status and a maximum prison sentence of 30 years. Voted most school spirit, and then you're in jail. It's like something you think you would never go through. I feel like my senior year was like, ruined. Reporter: Did she ever tell you about her sexuality? Not out rightly. You know not like "Hey, I'm a gay" or "Hey, I'm a lesbian," or "Hey, I'm bisexual." We never had that conversation. Reporter: Her mother claiming the prosecutor and the younger girl's family were motivated in part by an anti-gay bias. On Facebook she aired her daughter's shakespearean lament, writing of the younger girl's parents. "They were out to destroy my daughter. They feel like my daughter made their daughter gay." The family then came up with this line -- "Stop the hate, free Kate." I needed everybody to know what was going on, and for someone else to say you were right, like this is absolutely crazy and wrong. Reporter: Gay rights activists and others grabbed this digital gauntlet and rallied behind Kaitlyn and her family. Supporters donated tens of thousands of dollars. A petition against the prosecution got more than 300,000 signatures online. And this past summer Kaitlyn flew to New York to March in the world's largest annual gay pride parade. What does it feel like to, in some ways, become this icon of the gay community? It's pretty awesome because you know, the support from the community is just, it's overwhelming. But nice at the same time. Scared of losing my life, the rest of my life and not being able to go to college and be around kids and my sisters and my family. Reporter: If Kaitlyn were Kyle, how different would this be? My honest opinion is it would not be an issue. Reporter: The prosecutor offered Kaitlyn a plea deal. Including no prison time. She rejected the offer. She wanted a trial to prove her innocence. Tell me what you were fighting for.
This transcript has been automatically generated and may not be 100% accurate.