The parents of Amanda Knox, who is on trial for the murder of British student Meredith Kercher, are being investigated for defamation after they accused police of beating their daughter, Sky News reported.

It comes just hours after Curt Knox and his remarried wife Edda Mellas arrived in Italy for the closing stages of the trial.

Eighteen months ago Knox's parents gave an interview to the Sunday Times in which they said their daughter had ''been abused physically and verbally," Sky News reported.

Curt Knox, from Seattle, added in the interview: ''She told us she was hit in the back of the head by a police officer with an open hand, at least twice."

''The police told her, 'If you ask for a lawyer, things will get worse for you' and 'If you don't give us some explanation for what happened, you're going to go to jail for a very long time'.''

In June when Knox testified in her trial she repeated the accusations, saying it was a female officer who had hit her twice and called her a stupid liar - which was denied by both police and prosecutors.

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