New tests performed on a kitchen knife allegedly used in the 2007 murder of British student Meredith Kercher have revealed DNA traces of her roommate, Amanda Knox -- but not of the victim, according to reports.

Sky News reports that the new tests are part of the retrial of Amanda Knox and her former boyfriend Raffaele Sollecito, and their reported results were leaked before their scheduled release on Wednesday.

The kitchen knife was found in Sollecito's apartment in the wake of the murder, the Telegraph says. Initial tests appeared to show both Kercher and Knox's DNA on the knife, and it became an important part of the first trial, in which Knox and Sollecito were convicted.

However, the new reports raise the question of whether the knife was actually used in the crime. The defendants' lawyers argue that it is plausible for Knox's DNA to be on the knife without it having to do anything with the crime, since she cooked with it in Sollecito's home in the weeks leading up to the murder.

"The results of the report categorically exclude that the knife was the murder weapon," Sollecito's lawyer, Giulia Bongiorno, told The Guardian.

Amanda Knox and Raffaele Sollecito were convicted in 2009 for the murder of Kercher, Knox's British roommate. The pair was acquitted in 2011, but an Italian court overturned that acquittal in 2013. Knox is not attending the retrial.