The decision by the Court of Cassation adds a further twist to a long-running case whose initial handling was sharply criticised by independent forensic experts.
Prosecutors accused Amanda Knox and her ex-boyfriend Raffaele Sollecito of assaulting and killing Kercher in 2007.
They were initially found guilty and sentenced to 26 and 25 years in prison respectively.
In 2011, their convictions were overturned and they were released after serving four years.
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The family of the police officer who was murdered in the Westminster attack have thanked those who were with him 'in his last moments'.
Thousands of fans gathered for a public memorial honoring famous mother and daughter who died just a day apart.
More sunshine this Sunday as British Summer Time begins.