US student Amanda Knox's second appeal trial in the murder of her British roommate opened on Monday, but the star defendant was absent.

Italy's highest court ordered in March a new trial for Knox and her Italian ex-boyfriend, Raffaele Sollecito, overturning their acquittals in the gruesome 2007 slaying of Meredith Kercher. The Court of Cassation gave a harsh assessment of an appeals court acquittal in 2011, saying it was full of "deficiencies, contradictions and illogical" conclusions.

During opening statements, lawyers for Knox and Sollecito requested an array of new expert opinions and evidence to reach a definitive verdict, including examining the handle of the knife that was the purported murder weapon and the handling of the crime scene.