(CBS/AP) PERUGIA, Italy - A police official who conducted the original investigation in the Amanda Knox case insists there was no contamination on crucial pieces of evidence linking Knox and her co-defendant to the murder of her British roommate.
Patrizia Stefanoni, who examined DNA traces in the aftermath of the 2007 killing of Meredith Kercher, took the stand as Knox's appeals trial resumed after the summer recess. A verdict is expected by the end of the month.
Stefanoni was criticized by court-appointed experts, who have alleged glaring errors in the evidence gathering and possible contamination, including on a knife considered the murder weapon.
Stefanoni told an appeals court Tuesday that she could rule out contamination on the knife, which she insists contained Kercher's genetic profile.
Knox and her co-defendant and one-time boyfriend, Raffaele Sollecito, were convicted of sexually assaulting and killing Kercher in the apartment that Knox and Kercher shared while studying in Perugia.
Knox is serving a 26-year prison term. She denies wrongdoing.