Knox and Raffaele Sollecito, in the process of appealing their convictions in Rome in the November 2007 slaying of Knox's British roommate, Meredith Kercher, will be affected by the development in Thursday's supreme court hearing of a third convict in the case, Ivorian Rudy Guede, the Italian news agency ANSA reported.
Kercher, 21, of London was found with her throat slit following an alleged sex-game-gone-wrong in the apartment the two women shared.
Guede was sentenced to 16 years in prison for the murder. The court rejected his appeal and upheld lower court decisions against him.
Knox is appealing a 26-year prison sentence, and Sollecito is contesting a 25-year term.
The court said it was called upon only to assess Guede's guilt, but its pronouncement necessarily adversely affects the arguments of Knox and Sollecito that Guede was the only suspect guilty of the murder, ANSA reported.
On Knox and Sollecito's lawyers' requests, forensic experts earlier this month began re-examining disputed DNA evidence key in their first trial.
The experts' findings are scheduled for delivery on May 9 and an assessment hearing is scheduled for May 21.