Amanda Knox and Raffaele Sollecito have been found guilty of the murder of British student Meredith Kercher after judges in Italy overruled their previous acquittal.
It is the third time American Knox, 26, and Italian national Sollecito, 29, have faced trial over the death, in Perugia in 2007.
Neither defendant was in the courtroom as the verdict was announced, though Sollecito had attended the lengthy hearings.
Members of Ms Kercher's family were there to hear the verdict.
The co-accused 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.
Today, after lengthy deliberations, the court heard that both were guilty.
Rudy Guede, a drug dealer, is serving a 16-year sentence over the death.
The courts have said he did not act alone.
Speaking before the verdict was announced, Knox said she will only be extradited to Italy "kicking and screaming".
It is not clear whether Knox 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 said she was "frightened and saddened" and was going to appeal against the decision.
Knox described the ruling as "inconsistent and unfounded" and her co-accused was said to have been "astonished" with the way the court kept changing its mind.