Alleged weapon found in Raffaele Sollecito's flat was not used in murder, lawyers argue after forensic test results leaked

Forensic tests carried out on the knife alleged to have been used to kill the British exchange student Meredith Kercher have identified a minute DNA trace as belonging to Amanda Knox rather than the victim, according to leaked results.

In their report submitted on Thursday, forensic experts ordered by the Florence appeals court to carry out the further testing said there was "reasonable certainty" that the DNA trace was the Seattle-based student's, Italian media reported.

The results were viewed as a boost for Knox, as her lawyers argued that there was now no credible evidence linking the knife to the murder.

Six years after Kercher, a 21-year-old Leeds University student from Coulsden, Surrey, was brutally killed in the Italian university town of Perugia, both Knox and her ex-boyfriend, Raffaele Sollecito, are in the middle of a fresh appeal against their conviction for her murder.

The alleged weapon was found in Sollecito's flat, and Knox's lawyers have always argued it would be entirely plausible for her DNA to be on it.

"The results of the report categorically exclude that the knife was the murder weapon," claimed Giulia Bongiorno, Sollecito's lawyer. "It is the latest demonstration that there is nothing linking the crime with Raffaele and Amanda, because the only connection was the murder weapon, but this report excludes that it is it."

Having been found guilty of the killing in 2009 and cleared in 2011, Knox and Sollecito were sensationally drawn back into the long-running case earlier this year when Italy's supreme court overturned their acquittals and ordered a new appeals trial to take place in Florence.

The full report on the DNA trace testing is due to be examined in court on Wednesday at a hearing that Sollecito is expected to attend, for the first time in this third trial. Knox, a student at the University of Washington in Seattle, is staying away from the proceedings.

Initial forensic testing carried out in the original investigation appeared to show that there were traces of DNA belonging to both Knox and Kercher on the knife. Those findings were ruled unreliable in the first appeal, which overturned the convictions.