That testimony bolsters the defense, which claims the kitchen knife was not the weapon used in the bloody 2007 slaying of Knox's British roommate, 21-year-old Meredith Kercher.
As things stand, there's no confirmed DNA belonging to Kercher on the knife; one piece of DNA on its blade that was first attributed to Kercher has been disputed on appeal.
Expert Andrea Berti testified Wednesday that the minute new DNA trace from the knife's handle showed "considerable affinity" with Knox's DNA, while not matching that of Kercher. It also did not match the DNA of Knox's co-defendant Raffaele Sollecito or Rudy Guede, an Ivorian man who has been convicted separately in the brutal slaying.
Knox defense lawyer Carlo Dalla Vedova told The Associated Press that the testimony confirms their contention that the knife was used solely for preparing food. "The report confirms that this is a kitchen knife. It is not a murder weapon," Dalla Vedova said.
Luca Maori, Sollecito's defense lawyer, said the trace's very existence also indicated the knife had not been washed. "It is something very important," he said. "It is absurd to use it for a murder and put it back in the drawer."
The DNA evidence on the knife found in a drawer at Sollecito's place has been among the most hotly contested pieces of evidence in the original trial and now in two appeals.
Knox and Sollecito were convicted in 2009 of murdering Kercher, and sentenced to 26 and 25 years in jail, respectively. The conviction was overturned on appeal in 2011, freeing Knox to return to the United States where she remains for the latest appeal.
Prosecutors have contended the knife was the murder weapon because it matched Kercher's wounds, and presented evidence in the first trial that it contained Kercher's DNA on the blade and Knox's on the handle.
However, a court-ordered review during the first appeal in Perugia, where the murder happened, discredited the DNA evidence. It said there were glaring errors in evidence-collecting and that below-standard testing and possible contamination raised doubts over the DNA traces linked to Kercher on the blade, as well as Sollecito's DNA on Kercher's bra clasp.
Italy's highest court, however, ordered a fresh appeals trial, blasting the acquittal as full of contradictions and questioning failures to retest some of the DNA evidence in light of advanced new technology.
Sollecito addressed the court on Wednesday, as allowed by the Italian judicial system. He said he hadn't taken seriously enough the accusations at the beginning because he was too caught up with his new romance with Knox to grasp what was happening.
"Me and Amanda were living the dawn of a carefree romance and we wanted to be completely isolated in our love nest," Sollecito said.
He struggled with his composure as he pleaded with the court to acquit him. "I hope I'll have the chance to live a life, a life, because at the moment I don't have a real life," he said. "That's what I'm asking you."
The DNA trace is the last new piece of evidence to be entered in the latest trial. Prosecutors begin their summations later this month, followed by the defense in December. A verdict is expected in January.