Reuters – Italy's highest court was expected to rule on Wednesday on whether to uphold the conviction of American Amanda Knox and her former Italian boyfriend for the 2007 killing of British student Meredith Kercher.

The case, which has inspired books and films, has riveted media attention in Italy and the United States for eight years and the court's decision could trigger a legal battle between the two allies.

Knox, 27, and Raffaele Sollecito, 30, were convicted for the second time last year in the murder of 21-year-old Kercher, who was found stabbed to death in a house the women shared in Perugia, a university city in central Italy.

A confirmation of those convictions could trigger a complicated and drawn-out battle to try and extradite Knox from the United States. Sollecito, whose passport has been withdrawn pending the decision and who attended Wednesday's hearing, could be arrested.

The Court of Cassation's, which began its hearing on the case on Wednesday, could also overturn the conviction, and then either order yet another trial or effectively acquit the two -- though legal experts said that last option was unlikely.

Both Knox and Sollecito have maintained their innocence throughout.

Washington has refused to send military personnel to serve sentences in Italy in the past, but sparing a private citizen like Knox from extradition would be an "anomaly", said Pier Luigi Petrillo, Professor of Comparative Law at Rome's LUISS university.

"If an American citizen has been found guilty of a crime and in particular a serious crime such as murder on Italian soil, there is an obligation by the United States to extradite the American citizen," Petrillo said.

Some experts say a "double jeopardy" U.S. constitutional ban on retrial for the same offense after acquittal and the fact Knox was tried in absentia could count in her favor.

Knox has come to be seen in her home country as the victim of a botched investigation and an unwieldy legal system.

She and Sollecito were convicted at the first trial in 2009. That ruling was overturned in an appeal in 2011 and both were freed from prison. Knox left Italy for her hometown, Seattle.

The Court of Cassation later found faults with the previous trials and ordered a new one. The couple were re-convicted last year by a court in Florence, handing Knox a 28-1/2 year sentence and Sollecito 25 years.

The prosecution originally portrayed Knox as a fast-living party goer who killing Kercher when a sex game went wrong. The Florence verdict said the killing was more likely due to an argument between the roommates.

Ivory Coast-born Rudy Guede is serving a 16-year jail sentence for the crime after a separate trial. Judges ruled he did not act alone.

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