Amanda Knox Appeal Claims New Witness Can Prove She's Innocent

April 19, 2010— -- Lawyers for Amanda Knox, the American student convicted in Italy of murdering her roommate, say they have a new witness who can prove Knox wasn't present when her roommmate was killed.

Knox's lawyer told "Good Morning America" today 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.

"Why is Amanda Knox still in jail?" her attorney Theodore "Ted" Simon asked today on "GMA," calling the 22-year-old's conviction for the 2007 murder of British student Meredith Kercher "fraught with speculation."

Knox's legal team and her family are hoping the appeal will overturn her conviction and bring her home to Seattle.

"Amanda has zero history of violence at all, ever," Knox's mother Edda Mellas said. "Her first crime is not murder. It doesn't happen."

Knox was convicted along with her former boyfriend Raffaele Sollecito on Dec. 5, 2009. Sollecito's lawyer submitted his appeal last week. A third person, Rudy Guede, was convicted of taking part in the murder in a separate trial.

Simon said that new evidence in Knox's appeal and Sollecito's includes witness testimony that proves neither were even in Kercher's room the night of the murder.

"There's brand new information presented as part of Amanda's appeal by another person...that states for the first time that Amanda Knox and Raffaele Sollecito were not present or were not involved," Simon told "GMA."

The appeal will also challenge the validity of the prosecution's forensic evidence, particularly the reliability of DNA found on a knife in Sollecito's apartment that prosecutors claim was the murder weapon.

"All the forensic evidence points to Rudy Guede," Simon said. Guede was sentenced to 30 years, but that sentenced was reduced to 16 years on appeal.

"There is no forensic evidence that points to Amanda Knox," Simon said.

Knox Lawyers: No Motive, No Crime

Differing from the American judicial system, the appeals process in Italy allows for a re-examination of evidence presented during the trial, which Simon said they will use to Knox's advantage.

Her attorneys are once again asking for an independent evaluation of the DNA evidence, a request that was denied during her trial.

"This 200-page appeal persuasively demonstrates whatever evidence that was produced was insubstantial, unpersuasive and unreliable," Simon said. "It was fraught with speculation, conjecture and contradiction."

The appeal also claims Knox was denied her legal rights during the initial police interrogation when she gave conflicting statements about the night of the murder.

"She was not provided with an official interpreter. She was not provided with a lawyer," Mellas said. "She was smacked on the back of the head, she was threatened , she was screamed at."

The appeal will be heard by two new judges and six jurors. A decision is expected in the fall. If the appeal is unsuccessful, Knox can then appeal to Supreme Court in Rome

Knox's appeal came days after prosecutors filed their own paperwork, asking to extend Knox's prison term to a life sentence.

In an opinion issued last month, the two judges and six jurors from Knox's trial explained her 26-year sentence by saying they believed she participated in the murder and its cover up.

Prosecutors had presented several motives -- from robbery to tensions between the two girls -- but the judges and jurors decided there was no motive. The crime, they said, "happened at the spur of the moment in a drug-fueled escalation of a sexual assault."

Simon said the very fact that the Italian court dismissed the prosecution's varying theories for a motive should speak volumes about her innocence.

"Why would Amanda do such a thing without a motive?" he asked.

Simon said his client is doing her best behind bars.

"Under the circumstances we believe she's doing very well," he said. "I mean this is tough situation."

But the possibility that prosecutors may get their way and put Knox away for life is not something her parents are willing to accept.

"We will never leave her over there. She will come home no matter what it takes," her father Curt Knox said.

"Any parent would do that for her innocent child," Mellas said.

ABC News' Nikki Battiste contributed to this report