Transcript for Vanderbilt Rape Victim Apologized, Was 'Embarrassed'
Reporter: On the lush green campus of Vanderbilt university, the unspeakable happened to a 21-year-old coed. It breaks the heart of a veteran detective to have to show her that horrific video of the assault. She was just so sure that Brandon Vandenburg would never let anything happen to her and then when I told her she was crushed. Reporter: Later, judgment day has finally arrived for Cory Batey and Brandon Vandenburg. The pair on trial for aggravated rape inside a dorm room. Co-defendants tip Mckenzie and Brandon banks set to be tried at a later date. Little did she know, that day that had such great promise for her turned into her worst nightmare. A nightmare she relieved for a long time. And they almost got away with it. They almost succeeded. Not only did they violate the laws of the state, the very principles of human decency. Reporter: But in court, indecency and intoxication would take center stage. Hften did you do these pregame warm-up parties before you went out and hit the bars? This is something that everyone partakes probably before they go out. Reporter: As Vanderbilt student after student took the stand to testify. At any time did you attempt to speak to her? No, sir. At any time did you check on her welfare? No, sir. Reporter: No one alerted anyone. Not even the victim's roommate, Lauren miller, who noticed something odd the morning after the incident. So when you came outside, your best friend's shoe was on the lawn and her car is gone. Correct. So you call the police? I did not. I didn't report it because I didn't have a concern at the time. Reporter: But once Lauren saw her later that day, red flags went up. When I first saw her, my immediate reaction was like, "Whoa, what happened to you?" Reporter: She even took a photo of what looked like injuries on her friend's buttocks. You can clearly see some bruising on the cheek along with what appears to be some sort of imprint on her butt. Reporter: After days of listening to others talk about her, the victim herself testifies. "20/20" is altering her voice. I've never felt like that in my life. Reporter: For 90 minutes, she keeps the courtroom riveted with details of a hazy night at the tin roof and an evening that comes to a halt after sipping a blue beverage. Did you finish the blue drink? I don't remember finishing it. What's the next thing that you remember? I remember waking up in an unfamiliar room at eight something the next morning. Reporter: In a fog, she texts Brandon Vandenburg to fill in the blanks. In Brandon's version, he's the knight in shining armor. What did he tell you? I had gotten sick in his room and he had to spend the whole night taking care of me and that it was horrible. I apologized. I was embarrassed. Reporter: Brandon continued to lay on the guilt trip in texts. On the stand, she read some of those messages. I didn't do anything. I feel like I'm getting blamed for stuff that didn't even happen. I just want to cry. Me and a bunch of my teammates are probably going to get kicked off the team unless something changes. What was your main concern at that time? My main concern was protecting Mr. Vandenburg. Reporter: The pair meet up later that day. How was he treating you? He was being extremely kind. Nicer than usual. What happened next? He kissed me. Then he initiated intercourse. And how long did that last? A few seconds. Reporter: What the victim is never told by Brandon is that he and three others were involved in her sexual assault and videotaped the encounter to share with friends. Two months later, the victim will learn exactly how and who inflicted that pain when she watches the videos. Were you able to identify yourself? That was me. The video you did view, did it have audio also? It did. Did you hear a voice? I heard a voice I recognized. And whose voice did you hear on the video? Brandon Vandenberg. The horrific laughing from Brandon Vanderburg and just the awful degrading tone that they were using. Reporter: Brandon's not laughing anymore. He's watching stoically as his childhood best friends from California testify against him about trying to cover up the cell phone video. Joey quinzio saying he was pressured to lie to police. I was being coerced by Mr. Vandenburg and his attorney. Reporter: And miles Finley saying Brandon destroyed evidence. Did he tell you what happened to your cell phone? Yes. What did he say after? He said he smashed it and threw it in the lake. Reporter: During cross-examination Brandon's defense attorney seized on some of miles' text messages during the assault. "Dog kick that -- out or gang bang her. Don't let her wake up." You were giving him direction that night telling him what to do, weren't you, Mr. Finley? Don't look at him. Look up here at me. Why are you looking over there? I'm over here. Who are you looking at? Sir, could you please calm down, because I'm not yelling at you. Reporter: Eventually he does calm down and attempts to make a distinction that his client did not penetrate the victim sexually and therefore should not be charged with rape. He is taking responsibility for what he did. He shouldn't have taken those photographs. He shouldn't have sent those photographs. That is what he did. What he shouldn't have to take responsibility for is what he didn't do. Reporter: But for Cory Batey, the defense is tougher. Remember, he was seen on video touching the victim. So his legal team throws a hail Mary and calls Cory himself to testify, something defendants rarely do. Cory grew up in the rough part of Nashville and whose mom works at Vanderbilt appears nervous but is sure to make eye contact with jurors. At times, his memory is razor-sharp, but ask him how photos of the victim got on his phone, his mind goes blank. I didn't know they got there. I didn't remember. I didn't know what had happened to the young lady in the pictures and I deleted them immediately. Reporter: Cory estimates he had between 14 and 22 alcoholic drinks that night and claims he still can't remember what happened on the night in question. What, if any, recollection today do you have of that event? Not at all. Reporter: But then, a stunning admission by the 20-year-old defendant. One that is likely to send him to prison. I was just drunk out of my mind. This is just something I would never do in my right state of mind. I'm just sorry. Do you take responsibility for your conduct? After seeing the footage, I do. It was me. Reporter: And then he tries to speak directly to the victim. I would like to apologize. Reporter: Would that apology sway the jury's decision? When "20/20" returns the verdict is in. We the jury find Cory Batey -- Reporter: And the jurors speak out. But a revelation just hours ago
This transcript has been automatically generated and may not be 100% accurate.