A key witness in the appeal trial of Amanda Knox told the court in Italy in a dramatic confrontation on Monday that the young American woman killed her British housemate Meredith Kercher. "This splendid, marvellous girl was killed by Raffaele Sollecito and Amanda Knox," Rudy Guede, who has been been convicted separately for his part in the murder, said in a letter read out by prosecutors as he sat in the witness stand.