A court in Italy has ordered a new DNA test on the knife reported to have been used in the murder of British student Meredith Kercher in 2007.
The ruling came on the first day of the retrial of US student Amanda Knox and her former boyfriend Raffaelle Sollecito.
The prosecution believes Miss Kercher was forced into a sex game in the small town of Perugia six years ago, that ended with her throat being slashed.
Both Ms Knox and Mr Sollecito were sentenced to prison, but their convictions were overturned in 2011.
Neither is attending the hearing in Florence. The original trial was held in Perugia. The BBC reports the retrial was ordered after the prosecution appealed against the acquittal.
At the first session on Monday, lawyers for the two accused requested an array of new testimony and evidence be considered by the court.
Presiding judge Alessandro Nencini rejected most of the defence's requests, but agreed to test for DNA on a kitchen knife which the prosecution says was used in the murder.
Miss Kercher, 21, from south London, was an undergraduate at the University of Leeds and was studying on an exchange programme at the University of Perugia at the time of her death.