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 Senate has advanced a bill to reopen federal agencies after Democrats relented and lifted their blockade against legislation.
The explosion caused authorities to raise the alert level to four out of five, over fears a violent eruption is possible in just hours.
A senior police officer has accused internet firms of failing to respond to the growing online threat posed by paedophiles.