Amanda Knox said she will only be extradited to Italy "kicking and screaming", after judges reinstated her murder conviction for the death of British student Meredith Kercher.
Knox, who stayed in her native America for the trial, was sentenced to 28 years and six months and her former boyfriend Raffaele Sollecito jailed for 25 years.
It is not clear whether Knox, 26, will be expected to return to Italy to serve her jail term, but in a pre-recorded interview for BBC's Newsnight, she said: "I'm not willingly going back, no.
"It would feel like a train wreck. There's not a lot I can do after this appeal. They would order my arrest and the Italian government would approach the American government and say, 'Extradite her'.
"And I don't know what would happen. I'm still counting on an acquittal.
"I'll technically be considered a fugitive. I don't know what I will do though. I'm definitely not going back willingfully.
"They'll have to catch me and pull me back, kicking and screaming into a prison I don't deserve to be in."
Speaking after the case, Knox issued a statement in which she was "frightened and saddened" and was going to appeal against the decision.
Knox described the ruling as "inconsistent and unfounded" and h er co-accused was said to have been "astonished" with the way the court kept changing its mind.
Neither defendant was in the courtroom as the verdict was announced, though Sollecito, 29, had attended the lengthy hearings.
Members of 21-year-old Miss Kercher's family were there to hear the verdict - and said they would not be able to forgive those responsible for her death.
Miss Kercher, a Leeds University exchange student from Coulsdon, Surrey, was found with her throat slashed in the bedroom of the house she shared with Knox in Perugia, central Italy, in November 2007.
The defendants were originally found guilty of murder in 2009, and were handed jail terms totalling more than 50 years.
They were cleared nearly two years later - but the appeal court ordered a fresh trial in March last year.
Rudy Guede, a drug dealer, is serving a 16-year sentence over the death - though the courts have said he did not act alone.
Today, after lengthy deliberations, the court heard that both were guilty.
In a statement issued by Knox after the verdict, she said she was "frightened and saddened by this unjust verdict".
She said the grief of the Kercher family "will follow them forever" and said they "deserve respect and support".
The statement added: "I am frightened and saddened by this unjust verdict, having been found innocent before. I expected better from the Italian justice system.
"The evidence and accusatory theory do not justify a verdict of guilt beyond a reasonable doubt. Rather nothing has changed. There has always been a marked lack of evidence.
"My family and I have suffered greatly from the wrongful persecution."
Knox said this had "gotten out of hand".
"Most troubling is that it was entirely preventable," she said.
She described the investigation as "prejudiced and narrow-minded". She said there was an "unwillingness to admit mistakes" and added that there was a "reliance on unreliable testimony and evidence".
Knox said there was a "character assassination" as well as "inconsistent and unfounded accusatory theory", along with "counter-productive and coercive interrogation techniques that produced false confessions and inaccurate statements".
She added: "Clearly a wrongful conviction is horrific for the wrongfully accused, and it is also terribly bad for the victim, their surviving family and society."
Speaking outside the court, Knox's lawyer Luciano Ghirga said he would launch an appeal.
"For those that, like me, are convinced that Amanda is innocent, it is a very difficult time," he said. "We have to respect the verdict but we will challenge them.
"We're very sad at the moment. We will definitely try everything. This is not the final word. I am very upset by this decision.
"We continue to be brave, we have plenty of courage. The road to the next appeal is quite difficult but we are ready for a new battle."
Prosecutors claimed that Miss Kercher was the victim of a drug-fuelled sex game gone awry.
Knox and Sollecito have consistently protested their innocence and claim they were not in the apartment on the night Miss Kercher died.
Knox, who now lives in Seattle, said she would not attend the hearing in Florence due to being unable to afford to travel to Italy.
Sollecito - who has had his passport withheld - received a 25-year term. His solicitor Giulia Bongiorno said she had not yet spoken to her client.
She said: "He was prepared for any outcome. He is totally astonished why the court keeps changing mind in this way.
"The court gives credit to rumours. This is not a surprise. They (Knox and Sollecito) have always been considered the murderers."
Miss Kercher's brother Lyle, who was in court for the verdict, said he would not be able to forgive those responsible for his sister's death.
In an interview with Sky he said: "I think you'd have to be a very strong-willed - arguably religious - person to find that forgiveness. I think it is so easily forgotten what happened to Meredith.
"When I read reports even now, I find myself skimming past the paragraphs that refer to what actually happened to her because it is so horrific.
"I think anybody would just need to read in detail or know what happened to her to then question themselves - could they ever forgive someone who did that to their sister or daughter?"
Speaking after the verdict, Mr Kercher said: "No matter what the verdict, it was never going to be a case of celebrating anything.
"That's probably the best we could have hoped for."