FLORENCE, Italy — Expert testimony in the third murder trial of U.S. student Amanda Knox says tests on the presumed murder weapon show a new DNA trace belongs to Knox, not the victim.

The result bolsters the defense, which claims the knife was not the weapon used to kill British student Meredith Kercher. Another piece of DNA on the knife blade initially attributed to Kercher was disputed on appeal.

Knox defense lawyer Carlo dalla Vedova told The Associated Press that the evidence shows the knife was a simple kitchen knife used by Knox. Earlier evidence showed her DNA on the handle.

The expert testified Wednesday that the minute new trace showed "considerable affinity" with Knox's DNA, while not matching those of Kercher, Knox's co-defendant or an Ivorian man convicted in the 2007 slaying.