Amanda Knox's acquittal for the murder of her British roommate Meredith Kercher has been overturned by Italy's highest court which ordered a new trial.
Ms Kercher's family lawyer, Francesco Maresca, said after the ruling: "Yes, this is what we wanted." Knox called the decision "painful" but said she was confident in the truth.
The Court of Cassation ruled that an appeals court in Florence must re-hear the case against the American student and her Italian ex-boyfriend Raffaele Sollecito for the murder of 21-year-old student Ms Kercher. The exact issues that have to be reconsidered will not be known until the court releases its full ruling within 90 days.
Knox, 25, now a student at the University of Washington, said: "It was painful to receive the news that the Italian Supreme Court decided to send my case back for revision when the prosecution's theory of my involvement in Meredith's murder has been repeatedly revealed to be completely unfounded and unfair." She said the case must now be examined by "an objective investigation and a capable prosecution.
Ms Kercher's sister Stephanie said at home in Surrey: "There are a lot of unanswered questions still. We are very hopeful that it going back to court will help find those answers and find out the truth of what happened that night. Whilst we are not happy about going back to court, and it will not bring her back, we have to make sure we have done all we can for her.
Ms Kercher's body was found in November 2007 in her bedroom of the house she shared with Knox and others in Perugia, an Italian university town where the two women were exchange students. Her throat had been slashed.
Prosecutors said she was the victim of a drug-fuelled sex game gone awry. Knox and Sollecito denied involvement and said they were not even in the apartment, although they acknowledged they had smoked marijuana and their memories were clouded.
An Ivory Coast man, Rudy Guede, was convicted of the murder in a separate trial and is serving a 16-year sentence. Knox and Sollecito were also initially convicted of the murder and given long prison sentences, but were then acquitted on appeal and released in 2011. The high court's ruling overturned the appeals court acquittals.
"She thought the nightmare was over," Knox's lawyer Carlo Dalla Vedova said after the decision was released. Italian law cannot compel Knox to return from the US for the new trial. Mr Della Vedova said Knox would not go to Italy "for the moment" but would follow the case from home. He said he did not think the new appeals trial would begin before early 2014. Asked if she would come to Italy for the trial, he said: "I don't think so."
It is unclear what would happen if she was convicted in a new appeals trial. "If the court orders another trial, if she is convicted at that trial and if the conviction is upheld by the highest court, then Italy could seek her extradition," Mr Dalla Vedova said. It would then be up to the United States to decide if it honours the request. US and Italian authorities could also come to a deal that would keep Knox in the United States.