In November 2007, Seattle exchange student Amanda Knox and her Italian boyfriend Raffaele Sollecito, were arrested by the Italian police for the murder of their fellow University of Perugia student, British born Meredith Kercher. Prosecutors, at the 2009 murder trial, argued that Kercher had been the unwilling victim of a drug-fueled game of rough sex gone wrong. Kercher's half-naked corpse was discovered under a blanket in her bedroom. Her throat had been slit. Knox, then 20, and Sollecito, 24, were found guilty and sentenced to 25 years in prison.
An Italian appellate court, in October 2011, overturned the murder convictions on grounds the prosecution's evidence--unreliable witnesses and questionable DNA analysis--didn't support the government's theory of the case. The inmates were released from prison. Amanda Know moved back to Seattle where she's a creative writing student at the University of Washington. (She has written a book about her case that's awaiting publication. I presume the book is nonfiction.)
Italian prosecutors appealed the conviction reversal to the Court of Cassation, Italy's highest judicial body. On March 26, 2013, the high court overturned the appellate court's acquittal, and ordered a new trial. The decision was not based on the merits of the prosecution's case, but on procedural issues.
While the U.S. and Italy are parties to an extradition treaty, it's not a given that it will be honored in the Knox case. If she is not returned to Italy, she could be tried in absentia.