Perugia, Italy (CNN) -- Amanda Knox, the American student convicted of killing her British roommate Meredith Kercher in Italy, faced a surprise accusation Monday from another man behind bars for the murder. Rudy Guede refused to say Knox was not involved -- and prosecutor Giuliano Mignini read out a letter saying Guede thought the American and her then-boyfriend had killed Kercher. Guede wrote to a news website in the spring of 2010, after the three were convicted, referring to "a horrible homicide of a splendid young girl, Meredith Kercher, by Amanda Knox and Raffaele Sollecito." Mignini produced a copy of the letter on Monday during Knox's appeal against her conviction. Defense lawyers said they did not know of the existence of the letter before Mignini read it in court.
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NEW: Knox hopes DNA report due Thursday will help her defense, her father says
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Amanda Knox says she is "shocked" by the testimony of Rudy Guede
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Guede, convicted separately of killing Meredith Kercher, denies another convict's story
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Knox and her former boyfriend were found guilty in 2009 of killing Kercher in Perugia
Guede had been called as a witness to corroborate the story of another convict who told the court just over a week ago that Guede had said Knox and @placeholder were not involved.