Amanda Knox Update: Italian Supreme Court to rule whether American woman should be retried in murder case

(AP) ROME - Amanda Knox was "very anxious" as Italy's top criminal court heard arguments Monday from prosecutors appealing her acquittal in the murder of her roommate, her lawyer said.

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"She's carefully paying attention to what will come out," attorney Luciano Ghirga said as he arrived at Italy's Court of Cassation. "This is a fundamental stage. The trial is very complex."

Prosecutors are asking the high court to throw out the acquittals of Knox and her Italian ex-boyfriend in the murder of 21-year-old British student Meredith Kercher, and order a new trial.

Knox, now 25, and Raffaele Sollecito were arrested in 2007, shortly after Kercher's body was found in a pool of blood in her bedroom in the rented apartment she shared with Knox and others in the university town of Perugia, where they were exchange students. Her throat had been slashed.

Knox and Sollecito were initially convicted and given long prison sentences: 26 years for Knox, 25 for Sollecito. But in 2011 the appeals court acquitted them, criticizing virtually the entire case mounted by prosecutors in the first trial. The appellate court noted that the murder weapon was never found, said that DNA tests were faulty and added that Knox and Sollecito had no motive to kill Kercher.

After nearly four years behind bars, Knox returned to her hometown of Seattle and Sollecito resumed his computer science studies.

In the second and final level of appeal, prosecutors are now seeking to overturn the acquittals, while defense attorneys say they should stand.

"We're here to defend that sentence," said Sollecito's attorney, Giulia Bongiorno, who called the entire case "an absurd judicial process."

Monday's hearing began with one of the judges reading a summary of the gruesome case, including how Kercher essentially choked on her own blood from the stab wound. Neither Knox nor Sollecito was in court, though Sollecito's father attended.

If the court does throw out the acquittal and orders a retrial, Knox wouldn't have to return to Italy, as there is no requirement for defendants to be in court.

Defense attorneys said they were confident the acquittals would be upheld. "We know Raffaele Sollecito is innocent," Bongiorno said.

A verdict could come later Monday.

Knox and Sollecito have both maintained their innocence, though they said that smoking marijuana the night Kercher was killed had clouded their recollections.

Prosecutors have alleged that Kercher was the victim of a drug-fueled 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. Kercher's family has resisted theories that Guede acted alone.

The lawyer for the Kercher family, Francesco Maresca, was in court Monday.

The court is also hearing Knox's appeal against a slander conviction for having accused a local pub owner of carrying out the killing. The man was held for two weeks based on her allegations, but was then released for lack of evidence.

Complete Coverage of Amanda Knox on Crimesider