ROME -- Italian Supreme Court judges ruled Tuesday that American Amanda Knox should stand trial again for the death of her former roommate in Italy.
Knox spent four years in prison before an appellate court overturned her murder conviction in the 2007 death of Meredith Kercher in Perugia.
Knox, who returned to the United States in 2011, was not in court for Tuesday's ruling.
Prosecutors argued that despite the appellate decision, they still believe Knox and her former boyfriend, Raffaele Sollecito, are responsible for the death.
"We are still convinced that they are the co-authors of Meredith's homicide," Perugia prosecutor Giovanni Galati said, according to the Italian news agency ANSA.
The Supreme Court judges in Rome also ordered that Sollecito face a new trial over Kercher's death.
Judge Saverio Chieffi told the court he would publish the reasoning behind his decision within 60 days, after which the parties would have 45 days to present their case. This means the earliest possible date for a new trial would be July.
Knox may be ordered to return to Italy for the retrial, to be heard in an appellate court in Florence.
If she refuses, the Italian government could appeal to the U.S. government for her extradition.
But even if it does, Knox still not might end up before an Italian court.
U.S. officials might reject such a request because it violates the U.S. legal principle that a criminal defendant can't be tried twice on the same allegation, said Joey Jackson, a contributor for HLN's "In Session."
Italy lacks the absolute prohibition present in U.S. law preventing authorities from retrying a criminal defendant who has been acquitted of a charge.
"We have principles that are well-founded within our Constitution, one of which is double jeopardy," Jackson said. "So as a result of that, I think it would be highly objectionable for the United States to surrender someone to another country for which justice has already been administered and meted out. So I don't think or anticipate that that would happen."
Knox's lawyer, Luciano Ghirga, said Monday that her client was confident in the Italian legal system and hoped one day to return to Italy as a free woman.
The Supreme Court judges did not order her retrial on a charge of defamation.
Knox's conviction for defaming Patrick Lumumba, a club owner whom she accused of killing Kercher, was upheld in October 2011 by the same appeals court that cleared her of murder.
She was ordered to pay Lumumba 40,000 euros ($54,000) in damages. The court also sentenced her to three years in prison on that charge, but because she had already been held for four years, she was freed immediately.
The case began in 2007, after Knox moved to Perugia to study at the University for Foreigners of Perugia for one year
Knox, then 20, shared a room with British student Kercher, 21.
That November, Kercher's semi-naked body was found at the home, with her throat slashed.
Police arrested Knox and Sollecito, who was her boyfriend at the time.
Two years later they were convicted of murder, but were cleared when they appealed the verdicts in 2011.
Another man, Ivorian drifter Rudy Guede, was convicted separately of Kercher's killing.
Guede admitted having sexual relations with Kercher but denied killing her.
'Lack of evidence'
In legal paperwork published in December 2011, the judge in the case wrote that the jury had cleared the pair of murder for lack of evidence proving they were guilty.
Knox's family said last year the appeal was unwelcome, but no cause for concern.
"The appeal of Amanda's acquittal by the prosecution was not unexpected as they had indicated from the day of the verdict that they would appeal," a family statement in February 2012 said.
Knox has spent the last year and a half trying to resume a normal life, studying at the University of Washington in Seattle, her hometown.
She has written a book on her ordeal, titled "Waiting to be Heard," which will be published next month.
Francesco Sollecito, father of Raffaele, told CNN in a phone interview last year that the family was "not happy about the decision (to appeal). My son is trying to get back to normal life."
"We can do very little in this situation," he said, but as Italian citizens, they would have to accept the court's decision.
"We hope that the high court will finally put the words 'the end' to this story."
CNN's Ben Wedeman and Hada Messia reported from Rome and Laura Smith-Spark wrote in London. Ed Payne and Michael Pearson contributed to this report.