Amanda Knox's defense lawyer urged Italy's highest court on Wednesday to overturn the American's conviction in the 2007 murder of her British roommate, calling it a "grave judicial error."

Knox faces 28 ½ years in an Italian jail for the 2007 murder of 21-year-old Meredith Kercher in an apartment they shared in the university town of Perugia, after being convicted by a Florence appeals court last year along with her former Italian boyfriend, Raffaele Sollecito.

Sollecito's defense will make its case on Friday, when the case resumes before the Court of Cassation.

Winding up Wednesday's full day of arguments, Knox defense lawyer Carlo Dalla Vedova said the Florence court's conviction of Knox "is not justice, it is a distortion of the facts."

He argued, that based on analysis of blood stains, including two handprints on the victim's pillow, in Kercher's room and elsewhere in the house the two women shared, "there is not one trace of Amanda in the room of the crime."

"We are confronted with a very grave judicial error that must be set right," he said before asking the court to overturn the 2014 guilty verdict.

Knox maintains her innocence. She returned to the United States in 2011 after an earlier appellate court verdict acquitted the pair. She was awaiting the high court's decision in home town of Seattle, and is "worried, very worried," Dalla Vedova said.

"I don't think she is sleeping much," he added.

Sollecito spent the day in court, joined by family members and supporters. Defendants are not permitted to address the high court. He remains free but his passport was seized after the Florence court sentenced him to 25 years.

The Cassation Court's options include confirming the guilty verdicts, raising the question of extradition for Knox; overturning the convictions and ordering a third appeals trial; or overturning the convictions without a new trial, tantamount to acquittal.

Knox and Sollecito were convicted in 2009 of the murder, then acquitted by a Perugia appeals court in 2011. The Court of Cassation, however, threw out the acquittal in a scathing decision, remanding the case to a Florence appeals court, which convicted the pair.

The judge who presided over the appeals trial that acquitted the pair said the defendants have been "devastated" by the drawn-out, contradictory decisions.

Now retired, Claudio Pratillo Hellmann, in comments to the Italian news agency ANSA, predicted that the United States wouldn't agree to extradite Knox.

Kercher family lawyer Francesco Maresca said he hoped the Cassation Court would be reach a final decision, confirming the verdicts and ending the long legal saga.

"I hope that that family can remember the poor victim outside of the halls of justice after so many years," Maresca said.

The case generated intense media attention after Kercher's half-naked body was found in the apartment she shared with Knox and two Italian roommates in the university town of Perugia. Her throat was slit and she had been sexually assaulted.

Within days of her murder, suspicion fell on Knox and her Italian boyfriend of just a few days.

Knox has been portrayed alternately as a victim of a botched investigation and shoddy Italian justice, or a promiscuous predator who falsely accused a Congolese bar owner of the murder.

Arriving for Wednesday's hearing in the ornate Palace of Justice, Sollecito was swarmed by cameras. The courtroom was so packed with legal teams and journalists that the presiding judge moved the proceedings to a much larger courtroom during a break.

Prosecutor Mario Pinelli challenged the defense argument that there was no clear motive for the killing. He said focusing on the motive was a "slippery slope" and that the high court should just concentrate on the evidence.

Pinelli also focused on Knox's accusation against the bar owner, Diya "Patrick" Lumumba, who employed Knox. Lumumba, who is adamant about Knox's guilt, was in court watching the proceedings.

Knox and Sollecito denied involvement in the murder, and said they had spent the evening at Sollecito's place watching a movie, smoking pot and making love.

The Florence appeals court that convicted them most recently ruled that the pair acted in concert with Rudy Hermann Guede, a drifter born in the Ivory Coast who is serving a 16-year sentence for his role in the slaying and sexual assault. The presiding judge contended that Knox delivered the fatal knife blow because she wanted to "humiliate the victim."

Knox has called the reversal unjust and blamed an "overzealous and intransigent prosecution," ''narrow-minded investigation" and coercive interrogation techniques.

One of her attorneys, Luciano Ghirga, said before the hearing began that he was certain the high court would rule in her favor.

"I have always been confident," he said. "Amanda is innocent."

Sollecito's lawyer, Giulia Bongiorno, who will address the court Friday, said the guilty verdicts were "littered with errors and absolutely littered with contradictions and by an illogical motivation."