Amanda Knox and her former boyfriend are to face a retrial for the murder of a British student six years ago.
This morning Italy's highest criminal court overturned the acquittal of the American and ex-boyfriend Raffaele Sollecito in the death of housemate Meredith Kercher in 2007.
The Court of Cassation in Rome ruled today that an appeals court in Florence must re-hear the case against both over the 21-year-old's murder.
Knox said it was "painful" to have her acquittal overturned but she was confident in the truth, and said remaining questions about her case must now be examined by objective and capable prosecutors.
She said the Perugia prosecutors' theory of her involvement in the murder is "completely unfounded and unfair."
"No matter what happens, my family and I will face this continuing legal battle as we always have, confident in the truth and with our heads held high in the face of wrongful accusations and unreasonable adversity," she said.
The body of Meredith Kercher - from Coulsdon, Surrey - was found in November 2007 in her bedroom at the house she shared with Knox and other roommates in Perugia - an Italian university town where the two women were exchange students.
Her throat had been slashed.
Sister Stephanie Kercher - speaking at her Surrey home - said there were still "a lot of unanswered questions".
"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," she said.
"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.
"We still have a long journey ahead and we are very grateful for the support of the public and in Italy - we just want justice for Mez."
Ms Kercher's family lawyer, Francesco Maresca, said after the ruling: "Yes, this is what we wanted."
The exact issues which have to be reconsidered will not be known until the court releases its full ruling.
This morning, lawyers for Knox and Sollecito looked grim as they huddled with prosecutors and court officials to get details after the ruling was issued.
Lawyers for the Kercher family said they had got what they wanted.
The Italian court had considered the prosecutors' contentions that the 2011 acquittals of American Knox and her Italian ex-boyfriend should be thrown out and a new trial ordered.
Knox and Sollecito have both maintained their innocence, though they said that smoking marijuana the night Ms Kercher was killed had clouded their recollections.
Prosecutors had alleged that Kercher was the victim of a drug-fuelled sexual assault.
A young drifter from Ivory Coast, Rudy Guede, was convicted of the slaying in separate proceedings and is serving a 16-year sentence. Ms Kercher's family have resisted theories that Guede acted alone.
Today's high court ruling overturns the appeals court acquittals.
Italian law cannot compel Knox to return from the US for the new trial. The appellate court hearing the case could declare her in contempt of court but that carries no additional penalties.