The two court-appointed experts are looking into DNA traces on the knife believed to have been used to kill Meredith Kercher, a 21-year-old Briton who shared an apartment with Knox in Perugia, and into DNA traces found on the clasp of the bra Kercher was allegedly wearing at the time she was killed.
Knox, an American student, was convicted of sexually assaulting and killing Kercher and sentenced to 26 years in jail. Her boyfriend at the time of the murder, Raffaele Sollecito of Italy, was convicted of the same charges and sentenced to 25 years.
They both deny wrongdoing and their appeals trial is under way in Perugia.
The experts — originally scheduled to conclude their review on Monday, and then report to the court on May 21 — have asked for a delay of about 40 days, according to the ANSA news agency. The request was confirmed Friday by Francesco Maresca, a lawyer representing the Kercher family, and by Luca Maori, an attorney for Sollecito.
During the first trial, in the absence of a clear motive for the brutal killing, DNA evidence was crucial. Prosecutors maintained that Knox's DNA was on the knife handle, Kercher's DNA on the blade, and Sollecito's on the clasp of Kercher's bra.
The independent experts were mandated to either conduct a retest or, if not possible, assess the accuracy of the original testing. They have found that DNA traces were too small for a retest and are now reviewing the original analyses to assess whether they were reliable and up to standard, said Maresca.
The experts sought the review's extension because they want to study more documents regarding the tests, ANSA said.
The defense has always challenged the accuracy of the analyses presented in the first trial, saying traces were too low to be conclusive and alleging possible contamination. The bra was recovered at the crime scene only several weeks after the slaying. Kercher was found dead in the apartment she shared with Knox on Nov. 2, 2007, her throat slit.
The review was granted at the defense's request and assigned to two forensic experts of La Sapienza University in Rome. It takes place in the presence of experts appointed by the parties.
Maresca said the request was simply "dictated by the need to understand everything definitely," and did not speculate what it might mean for the ultimate outcome of the trial. Maresca is part of the trial because the Kerchers are civil plaintiffs in the case.
The next hearing will still be held on May 21. But the court will hear remaining witnesses, rather than the evidence review, and set a calendar, the lawyers said. The experts will likely present their findings to the court between late June and early July.