American Knox, 22, was sentenced last month to 26 years in jail for the sexual assault and murder of British student Meredith Kercher.

But she continues to protest her innocence and Philadelphia-based criminal defence lawyer Theodore Simon has now joined her legal team as her US consultant, the Knox family said.

He will work with Knox’s Italian lawyers, Luciano Ghirga and Carlo Dalla Vedova, and will recommend legal strategies that Knox could apply when launching her appeal against the verdict.

The appeal process is expected to begin in March and is thought to be unlikely to come to court before the autumn.

Mr Simon said: “Amanda’s conviction stands as a tragic example of a wrongful conviction which requires meaningful review.”