Amanda Knox update: DNA evidence re-tested, Rudy Guede points the finger

The ongoing legal struggle of Amanda Knox, an American accused of murdering her roommate while studying abroad in Italy, has grown more complicated. A letter written in 2010 by Rudy Guede, who has already been found guilty of the murder of Meredith Kercher, the roommate, says that he believes Knox and her then-boyfriend, Raffaele Sollecito, murdered Kercher.

Guede, who is currently serving 16 years in prison for the murder, refers to the event as "a horrible homicide of a splendid young girl, Meredith Kercher, by Amanda Knox and Raffaele Sollecito," CNN reports.

Knox was shocked by his allegation. "The only time that Rudy Guede, Raffaele Sollecito and I were in one room together was in a court room.... He knows what the truth is. I don't know what happened that night," she said in a testimony on Monday. That day's hearing was the first time that Guede, Knox, and Sollecito were in the same court room in years.

When asked to clarify his letter on the stand, Guede said it "was not up to me to say who was the killer."

Knox and Sollecito have already served close to four years in prison, and they continue to appeal their guilty verdict.

Forensic evidence is now being retested as part of the appeal, including a knife that was said to have Knox's DNA on the handle and Kercher's flesh in a groove on the blade. The sample is said to be so small that it could not be double-tested, as is standard in murder cases.

Additionally, the defense has asked for a retest of DNA found on the clasp of Kercher's bra, which was not collected from the scene until six weeks after the crime. The findings are expected to be revealed on Thursday.