Prosecutors in the trial of American student Amanda Knox, who was cleared last October of the 2007 murder of British housemate Meredith Kercher, filed a motion Tuesday to appeal against the verdict before Italy's highest court.
Prosecutors Giovanni Galati and Giancarlo Costagliola said in their motion that acquitting Knox and her ex-boyfriend Raffaele Sollecito was "contradictory and illogical."
Italian law permits prosecutors to appeal against not guilty verdicts. Now the Court of Cassation must rule whether there were any procedural irregularities that give grounds for a retrial.
Seattle-native Knox and Italian Sollecito won their appeal against a 2009 verdict that found them guilty of murdering the 21-year-old Kercher during what prosecutors said was a drug-fuelled sexual assault.
The verdict in October, a severe embarrassment to the Italian justice system, came after independent forensic investigators sharply criticized police scientific evidence in the original investigation, saying it was unreliable.
Kercher's half-naked body, with more than 40 wounds and a deep gash in the throat, was found in the apartment she shared with Knox in the Umbrian hill town of Perugia where both were studying.