Amanda Knox, the American convicted in December 2009 of sexually assaulting and murdering her British roommate in Italy, is "cautiously optimistic" as she begins the lengthy appellate process in Perugia, Italy, her best friend said Saturday.

Two forensic experts from Rome's La Sapienza University were sworn in Saturday by Italian judge Claudio Pratillo Hellman, taking an oath to uphold objectivity as they retest crucial forensic evidence used to convict Knox, 23, and her former boyfriend Raffaele Sollecito, of killing Meredith Kercher in Perugia.

The experts' work begins on February 9 and they must conclude their analysis by May 9. Results will be presented to the two-judge and six layperson jury on May 21.