Amanda Knox pauses emotionally while speaking during a news conference at Sea-Tac International Airport, Washington after landing there on a flight from Italy, in this October 4, 2011, file photo. 
 
 NEW YORK The possibility that American Amanda Knox could be convicted of murder and extradited to Italy for punishment could force U.S. courts to enter legal territory that is largely uncharted, legal experts said. 
 
 Italy's top court on Tuesday ordered the retrial of Knox, 25, for the 2007 murder of British student Meredith Kercher. 
 
 The move potentially pits a U.S. constitutional ban on double jeopardy, or being tried twice for the same offense after an acquittal, against international extradition agreements, experts said. 
 
 The issue hinges on whether a lower court decision overturning her conviction amounted to an acquittal, they said. 
 
 If Knox is retried after she was acquitted, that would violate her constitutional rights, said Christopher Blakesley, a law professor at the University of Nevada Las Vegas who specializes in international criminal law. On the other hand, the United States entered into an extradition treaty and, in doing so, accepted Italy's criminal justice system, he added. 
 
 "If Knox is found guilty, there's still a whole lot of room for battle before she would ever be extradited," Blakesley said. 
 
 Knox and her former boyfriend, Raffaele Sollecito, were accused of killing 21-year-old Meredith Kercher during a drug-fuelled sexual encounter in Perugia, Italy. The two were found guilty in 2009 and sentenced to 26 and 25 years in prison respectively. 
 
 In 2011, an appeals court, comprised of a panel of judges and lay jurors, overturned the convictions of Knox and Sollecito after forensic experts challenged evidence from the original trial. Knox and Sollecito were released after four years in prison, and Knox returned to her family home near Seattle. 
 
 Prosecutors and Kercher family lawyers appealed to Italy's high court, the Court of Cassation, calling the prior ruling "contradictory and illogical." 
 
 On Tuesday, the Court of Cassation agreed to overturn the appeals court's acquittals. The high court has not yet provided a full reasoning for its decision, and a date has not yet been set for the new trial, which will be held before a different court of appeals in Florence. 
 
 Knox's Italian lawyer, Carlo Dalla Vedova, said via email that the new trial would likely occur in late 2013 or early 2014. Knox does not intend to return to Italy for the proceeding, he said, and the court of appeals can retry the case in absentia. 
 
 The Italian government could ask for extradition once the Italian courts have reached a final decision, Dalla Vedova said. If it does, the U.S. Department of State would then have to decide whether to act on the request. If the State Department chooses to comply, it would then deploy the U.S. Attorney's Office to a U.S. court to seek Knox's extradition. 
 
 What is unpredictable is how such a case would play out in front of a U.S. judge who would have to weigh the U.S. constitutional protection against double jeopardy with the 1984 bilateral extradition treaty between the United States and Italy. The treaty contains a provision that attempts to protect against double jeopardy, but it is not clear whether that provision would bar extradition in Knox's case. 
 
 The legal question would be whether Knox was acquitted, as U.S. courts would define the term, or whether the case was merely reversed and still open for further appeal, said criminal lawyer and Harvard Law Professor Alan Dershowitz. 
 
 "It's very complicated, and there's no clear answer. It's in the range of unpredictable," Dershowitz said. 
 
 Much of the complication stems from the differences between the Italian and U.S. legal systems. In the United States, if a defendant is acquitted, the case cannot be retried. 
 
 In Italy, prosecutors and lawyers for interested parties, such as Kercher's family, can file an appeal. Unlike American courts of appeal, which only consider legal errors in the courts below, Italian courts of appeal, which are comprised of both judges and jurors, can reconsider the facts of a case. 
 
 Depending on the Italian high court's reason for overturning Knox's acquittal, it is possible that the court of appeals could consider new evidence that's introduced, said Dalla Vedova. As a result, a defendant can effectively be retried in the course of one case in Italy. 
 
 Dalla Vedova said the high court's decision does not raise a double jeopardy problem because the retrial would not be a new case but rather a continuation of the same case on appeal. 
 
 Other defendants who have been acquitted in other countries and then convicted on appeal have attempted to raise the double jeopardy principle to avoid extradition, without much success, said Mary Fan, a law professor at the University of Washington who specializes in cross-border criminal law. 
 
 The text of the treaty prevents extradition if the person has already been convicted or acquitted of the same offense by the "requested" country, which would be the United States in Knox's case because Italy would be requesting extradition from the United States. Because Knox was never prosecuted or acquitted for homicide in the United States, the treaty's double-jeopardy provision would not prevent Knox's extradition, said Fan. 
 
 While the issue is rare in the United States, several courts have rejected the double jeopardy argument in similar cases. In 2010, a federal court in California found that a man who was acquitted of murder in Mexico and later convicted after prosecutors appealed the acquittal, could not claim double jeopardy to avoid extradition to Mexico. That court cited a 1974 decision from the 2nd U.S. Circuit Court of Appeals in New York, that reached the same conclusion with respect to Canadian law, which also allows the government to appeal an acquittal. 
 
 When asked about the potential extradition of Knox at a press briefing on Tuesday, a spokesman for the U.S. State Department said the question was hypothetical and declined to comment. 
 
 (Reporting By Terry Baynes; Editing by Sandra Maler) ||||| Media caption The BBC's Alan Johnston in Rome says there could still be "years to go" in the case 
 
 Amanda Knox and ex-boyfriend Raffaele Sollecito have had their acquittals for killing Briton Meredith Kercher in 2007 overturned and face a re-run of their appeal, Italy's top court has ruled. 
 
 The pair spent four years in jail but were freed on appeal in 2011 largely on the grounds DNA evidence was flawed. 
 
 Miss Knox said the news was "painful" but Miss Kercher's sister said she was happy with the decision. 
 
 Italian law cannot compel Miss Knox to return from the US for the review. 
 
 The American student lives in Seattle but, if convicted, Italy could seek her extradition. 
 
 Analysis The decision took longer than expected - two days. The prosecution argued successfully that the appellate court's decision to quash the original convictions had been made by a judge who had "lost his bearings". Sloppy forensic investigations by police are frequently cited in Italian murder trials and some high-profile cases like the murder of the British student are never fully solved. The reasons for the latest decision will not be made public for another three months. The clinching argument for a retrial appears to revolve around another accused, Rudy Guede, who is serving 16 years for the murder. "He didn't have an ectoplasm for an accomplice," the prosecutor argued. And while interest remains high in the Knox case, a new murder overnight in Perugia grabbed public attention. Few details are yet known about the victims of, or the motives for, this latest crime. 
 
 In a statement, Miss Knox 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 added: "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." 
 
 A lawyer for Mr Sollecito, Giulia Buongiorno, said: "Today is Raffaele's birthday and I hoped it was an occasion to tell him and his family that everything was fine and over. Unfortunately I had to let them know that our legal case is still on and obviously they were very upset." 
 
 Mr Sollecito - who is now studying in Verona - will not have to return to jail while the new appeals process goes ahead. 
 
 Kercher family lawyer Francesco Maresca welcomed the decision to overturn the appeal. 
 
 "This is an important day for the Italian justice system," he said outside the court. 
 
 Miss Kercher's older sister, Stephanie, welcomed the decision as a step forward. 
 
 "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," she said. 
 
 Miss Knox, now 25, and Mr Sollecito, 29, were originally sentenced to 26 and 25 years in prison for killing and sexually assaulting Meredith Kercher. 
 
 Kercher murder: Timeline Image copyright PA 1 November 2007 : Kercher is killed at her apartment in Perugia. Police find her a day later. 
 
 : Kercher is killed at her apartment in Perugia. Police find her a day later. 6 November 2007 : Kercher's US housemate Knox is arrested, along with Sollecito and Congolese national Patrick Diya Lumumba. 
 
 : Kercher's US housemate Knox is arrested, along with Sollecito and Congolese national Patrick Diya Lumumba. 20 November 2007 : Rudy Guede detained in Germany and extradited to Italy. Mr Lumumba released without charge 
 
 : Rudy Guede detained in Germany and extradited to Italy. Mr Lumumba released without charge 28 October 2008: Guede sentenced to 16 years. A judge rules Sollecito and Knox will face a murder trial 
 
 Guede sentenced to 16 years. A judge rules Sollecito and Knox will face a murder trial 4 December 2009: Knox and Sollecito found guilty of murder and sexual violence, and jailed for 26 and 25 years 
 
 Knox and Sollecito found guilty of murder and sexual violence, and jailed for 26 and 25 years 3 October 2011: Knox and Sollecito acquitted 
 
 Knox and Sollecito acquitted 26 March 2013: Re-run of appeals ordered. Acquittals overturned Kercher murder: Timeline Profile: Amanda Knox Profile: Raffaele Sollecito 
 
 Rudy Guede was convicted in a separate trial and sentenced to 16 years. The Ivory Coast national was found guilty of sexually assaulting and stabbing Ms Kercher. He admitted to being at the house on the night of the killing, but denies murder. 
 
 'Illogical' 
 
 Meredith Kercher, 21 and from Coulsdon in south London, was in Italy on a year abroad from Leeds University when she was killed in Perugia in November 2007. 
 
 She was found dead in her bedroom in the cottage she shared with Miss Knox. Her semi-naked body had more than 40 knife wounds, including a deep gash to the throat. 
 
 Prosecutors believed she was killed in a brutal sex game that went wrong. 
 
 Media caption Stephanie Kercher: "It's a step forward for us" 
 
 Miss Knox and Mr Sollecito were acquitted in October 2011 by an appeals court that criticised the prosecution case and noted that the murder weapon had never been found, that DNA tests were faulty and that no murder motive was provided. 
 
 Prosecutors appealed against that ruling and argued at the Court of Cassation on Monday that the acquittals were "contradictory and illogical". 
 
 Addressing the court, prosecutors urged the judges to "make sure the final curtain does not drop on this shocking and dire crime". 
 
 The court examined whether there had been procedural irregularities, rather than looking at the details of the case, and it will announce the reasons for its ruling within 90 days. 
 
 Lawyers for Miss Knox and Mr Sollecito looked grim-faced on Tuesday as they tried to get the details of the ruling from the court. 
 
 Knox lawyer Carlo Dalla Vedova said the decision was "shocking" and wanted to know the "motivations" for the ruling. 
 
 "She thought the nightmare was over," he said, adding that it was unlikely the new hearing would be held before early 2014. 
 
 Miss Knox and Mr Sollecito spoke to each other by telephone after the ruling was announced, according to a friend of Mr Sollecito quoted by the Italian news agency Ansa. 
 
 The new hearing will take place in Florence because Perugia has only one court of appeal.
– Yet another ruling in the Amanda Knox case is coming from Italy's highest court today. Knox and then-boyfriend Raffaele Sollecito were convicted in the 2007 murder of Meredith Kercher in 2009, acquitted on appeal in 2011 (at which point Knox returned to the US), had that acquittal overturned in 2013, and were then found guilty again last year. As the New York Times and the AP report, Italy's top court, the Court of Cassation, has a number of options: Confirm the convictions: That would mean Italy would likely attempt to extradite Knox, who has maintained her innocence and vowed not to return to the country willingly, though there is a chance the Justice Ministry would decline to do so. Sollecito, who is still in Italy, would go to prison immediately to serve his sentence. Order new appellate trials for Knox and/or Sollecito: Yes, you read that right: This saga may still not be over. If this court decides to throw out all or part of the appeals court's guilty verdict, it will likely order a third trial. (To give you an idea of how long this could go on, one 1972 murder case went to the Court of Cassation nine times before a final verdict was issued, 28 years later.) Throw out the guilty verdict without ordering new trials: This would amount to an acquittal, leaving Knox free to visit Italy without fear of arrest, but the AP notes that "such a decision is rare." If an extradition request is made for Knox, a professor of international law tells the Times the US will likely grant it, though it would be a "hard" decision. The two countries do have an extradition treaty, and another expert tells the AP there is no formal reason—though there are a number of political ones—for Italy to not bother asking in the first place. (Some have argued the concept of "double jeopardy" could be used to block Knox's extradition, though others have debunked that idea.) It's not clear when the ruling is expected, but the BBC's live updates noted that the hearing was "underway" as of 7am Eastern time.