Knox and Sollecito are both appealing their convictions, but in April, the Italian prosecutors also filed an appeal, asking the court for a tougher sentence than the 26 years she was given.
The prosecution did not specify the sentence it wants imposed on Knox, but by arguing that the court should have considered an aggravating circumstance in handing out Knox's punishment, a life sentence would be almost automatic.
Lawyers for Knox say that they are confident that new evidence in the 200-page appeal of her murder conviction will force Italian courts to take a hard look at the validity of her prison sentence.
"I am very hopeful given the nature of the Italian appeals system," Curt Knox said. "I am hoping that with additional review of the forensics, and common sense regarding that fact that there is no DNA of Amanda in the room where [Kercher] lost her life, will help [the judges and jurors] see the truth that Amanda had nothing to do with this tragedy. I am quite hopeful."
A Knox lawyer told ABC News that new evidence in Knox's appeal and Sollecito's includes witness testimony that proves neither were in Kercher's room the night of the murder.
One alleged witness is a jailed Italian man who accuses his own brother in a legal deposition of killing Kercher, Knox's legal team told ABC News.
Luciano Aviello, who is tied to the Italian Mafia and currently serving a 17 year prison sentence, told Knox's lawyers in a video-taped prison interview in March that his brother Antonio showed up at his house in Perugia wearing a bloodstained jacket the night of Nov. 1, 2007, the night that Kercher was killed.
Aviello claims his brother told him that he broke into a house and killed a woman.
Antonio Aviello then asked his brother to hide the bloody knife and the keys to the Perugia apartment where Kercher and Knox lived, he claimed in the deposition.
"I hid everything under a little wall behind my house and covered it with soil and stones. I am happy to stand up in court and confirm all this and wrote to the court several times to tell them, but was never questioned," Luciano Aviello said.