"I'm going to fight this to the very end," she said in an interview with Robin Roberts on ABC's "Good Morning America. Knox said she was caught off guard by the decision of the Italian court.
"It hit me like a train. I didn't expect this to happen. They found me innocent before; how could they?" Knox had remained in Seattle during the trial.
That person, surrounded by others and covered by a coat, got into a vehicle and was driven away. When asked how Knox was doing, her mother, Edda Mellas said, "She's upset. How would you be?"
Knox said in a written statement that she was "frightened and saddened," she "expected better from the Italian justice system," and "this has gotten out of hand."
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The court reinstated a guilty verdict first handed down against Knox and Raffaele Sollecito in 2009. The verdict was overturned in 2011, but Italy's supreme court vacated that decision and sent the case back for a third trial in Florence.
In her statement, Knox acknowledged the family of Meredith Kercher, her roommate in Italy.
"First and foremost it must be recognised that there is no consolation for the Kercher family. Their grief over Meredith's terrible murder will follow them forever. They deserve respect and support," she said.
Meanwhile, police in Italian town of Florence today found Amanda Knox's ex-boyfriend near Italy's border with Slovenia and Austria, hours after he and the American student were convicted for a second time in the death of British student Meredith Kercher.
Raffaele Sollecito's lawyer, Luca Maori, said his client was in the area of Italy's northeastern border because that's where his current girlfriend lives, and that he went voluntarily to police.