ROME » Amanda Knox was waiting anxiously today to hear whether her ordeal is over or whether she will face trial again, as Italy’s top criminal court considered whether to overturn her acquittal in the murder of her roommate.

"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 American 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, who turns 29 on Tuesday, 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.

The court can decide to confirm the acquittal, making it final, or throw out the Perugia appellate court ruling entirely or partially, remanding the case to a new appeals court trial.

In that case, Italian law cannot compel Knox to return to Italy, although a court could declare her in contempt of court, which carries no additional penalties.

Prosecutor general Luigi Riello argued before the court that there were ample reasons "not to bring down the curtain on the case."

Riello said the appellate court was too dismissive in casting aside DNA evidence that led to the conviction in the lower court, arguing that another trial could make way for more definitive testing.

Neither Knox nor Sollecito was in court for the hearing, which opened with a summary of the gruesome murder, although Sollecito’s father attended.

Defense attorneys said they were confident the acquittals would be upheld. "We know Raffaele Sollecito is innocent," said Sollecito’s attorney, Giulia Bongiorno, who called the entire case "an absurd judicial process."

A verdict could come later today.

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 today.

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.

Riello argued that conviction should stand because "you cannot drag in an innocent person while exercising your right to a defense."