Tonight, Seattle college student Amanda Knox speaking out for the first time since that bombshell guilty verdict, a reversal that once again puts her freedom in jeopardy. For the past 6 1/2 years, her... See More
Tonight, Seattle college student Amanda Knox speaking out for the first time since that bombshell guilty verdict, a reversal that once again puts her freedom in jeopardy. For the past 6 1/2 years, her fate has been in the hands of the Italian justice system. Guilty, not guilty, and now guilty again. But tonight, she comes out strong saying she's not about to give up her fight. And in her first and only interview since the surprising new verdict, here's ABC's Olivier vargas. It was a moment of raw anguish, Amanda Knox clearly shaken by the news. An Italian court had convicted her for a second time of murder. I was with my family and I actually was able to find an Italian TV station online. My first reaction was no, this is wrong and I'm going to do everything I can to prove that it is. Nearly 28 months after being acquitted of killing british roommate Meredith Kercher while both were studying in perugia, Italy, another reversal of fortune. Amanda was sentenced to 28 1/2 years in prison. Her Italian boyfriend of one week was given 25 years. This really has hit me like a train. I did not expect this to happen. I really expected so much better from the Italian justice system. They found me innocent before. How can they say that it's guilt beyond a reasonable doubt. Knox vowed to keep fighting, a fight that's already gone on for 6 1/2 years. Next, her lawyers will wait for the court's reasoning. And then another appeal. We have to go to the supreme court. We have to understand the motivation behind what happened, and that happens within 90 days. Reporter: But could she be ultimately extradited to Italy? Are you prepared for that? I'm not. I will never go willingly back to the place where I -- If Italy's highest court upholds this ruling, Amanda Knox is a convicted murderer in Italy. They are going to say we want her back on our soil. The U.S. Is going to have to make a difficult decision. Because in most cases where someone has been convicted of murder, the U.S. Would extradite them. Reporter: Ted Simon is Amanda's U.S. Attorney and he argues she's already been found innocent. How did this jury, this panel of judges come up with a different verdict? Come up with guilty beyond a reasonable doubt. I think to a logical mind it's somewhat incomprehensible because there's no meaningful difference. There's no new evidence and there's certainly not any new favorable evidence for the prosecution. Amanda was home in Seattle with her family when the verdict came. I hear the word guilty, I understood that won one in Italian. Of course, you know, all of our hearts sank. From the start, the knoxs has been cutting in a nightmare. They sent their young daughter off for a dream year abroad studying Italian. Never thinking act the vast differences between the two legal systems in Italy and the U.S. In the Italian system, you can actually have new trials in the appellate court. And that's what happened here. If you're accused of a crime in Italy, you are in big trouble. Guilty until proven innocent. Another proven here that Amanda and rafaelle, they only had alibis for each other. Knox an solecito were soon arrested. Overnight, Knox became a murder suspect and an international media obsession. In December 2009, the two were convicted of murder after a dramatic year-long trial. A trial full of character accusations against Knox. And full of shifting motives. There were no eyewitnesses and no physical evidence. The prosecutor pinned his case on minute amounts of DNA found on a kitchen knife they claimed was the murder weapon, a fact that was essentially ruled out in the most recent case. In the first trial, Knox was sentenced to 26 years in prison. The verdict devastated her family. Anger, disbelief on how a judicial system could even come up with a verdict like this. It's beyond me. This is completely unjust and I'm in complete shock. Reporter: The Knox family made dozens of trips overseas and spent every penny that they had. More than $1 million fighting the charges. Finally an appeals court agreed to take up the case, casting doubt on the evidence and pointing to shoddy police work. Near the end of that second trial, I confronted the prosecutor on the street. Do you have a moment, please? Reporter: After his initial reluctan reluctance -- just one moment. The prosecutor relented. Why are you asking for life? They killed with no motive. The law dictates they must go to prison for life. Reporter: But then a dramatic decision. The appeals court overturned Amanda's conviction. She flew home to Seattle. What's important for me to say is just thank you to everyone who has believed in me. Reporter: Then just as Knox was beginning her new life, Italy's highest court overturned the acquittal last year. Amanda couldn't believe it. I'm going to keep fighting this. I'm going to keep fighting this and I'm not going to stop fighting this. That's all. The truth will come out and that's all. Reporter: Today, that truth is that she again stands convicted. For Meredith Kercher's family, whatever the courts ultimately decide, this will never really be over. We're stl onill on a journey to the truth. And it may be the fact that we don't ever really know what happened that night. Reporter: Today, Amanda acknowledged the Kercher's pain. I just want them to know that I really understand that this is incredibly difficult. They have also been on this never ending thing, and that when the case has been messed up so much, like a verdict is no longer consolation for them. And that just the very fact that they don't know what happened is horrible. Reporter: One more twist today in a case that has had so many. Rafaelle solecito traveling with his new girlfriend in northern Italy was stopped by police. He was allegedly trying to cross the border into Austria. His passport was taken, but he was released and remains free for now. Solecito is in a tougher spot, because he's an Italian citizen. And he doesn't have the protections of another country to go to, force an extradition fight. So without the ability to force an extradition fight, he could very well be serving time for this crime. He is vulnerable. And I don't know what I would do if they imprisoned him. It's maddening. Amanda and her family had hoped their nightmare would end with this latest verdict. Inste instead, they vow to fight to clear her name. Reporter: Is this young woman ever going to be free of this, do you think? It's certainly going to go on for a long time with no resolution near sight. Reporter: Who knew one year abroad could lead to what could be a lifetime ordeal. I'm going to fight this until the very end. And it's not right and it's not fair. Reporter: For "Nightline," I'm Elizabeth vargas in new York.
This transcript has been automatically generated and may not be 100% accurate.