The three suspects being held over the murder of British student Meredith Kercher are due to make a final appeal to be freed in Italy's highest court.
Judges in Rome will hear arguments from defence lawyers requesting the release of US student Amanda Knox, her former Italian boyfriend Raffaele Sollecito and Ivory Coast national Rudy Hermann Guede.
The three are being held in connection with the death of Meredith, a 21-year-old from Leeds University who was spending a year studying in Perugia.
She was found dead last November, half-naked in a pool of blood in the apartment she shared with Knox. She died from a stab wound to the neck.
Prosecutors have said she was killed resisting sexual assault, and they are investigating the three suspects on suspicion of murder and sexual violence.
Knox, 20, and Sollecito, 24, have been jailed since November. Guede, 21, was arrested in Germany and later extradited to Italy. He is believed to have fled shortly after the murder.
All three suspects deny being involved.
Judges in Perugia have already rejected defence requests to release the three. Lawyers have said they expect the justices of Italy's highest court, the Court of Cassation in Rome, to issue a decision on their appeal after the closed hearing.
The Perugia judges have ruled that the three could be held for up to a year while the case is investigated.
The suspects have not been formally charged.