An Italian judge presiding over the newest trial of Amanda Knox today ordered forensic experts to test a new "trace" of DNA on a knife that prosecutors claim is the weapon that killed Knox's roommate Meredith Kercher.
Interested in ?Add as an interest to stay up to date on the latest news, video, and analysis from ABC News.
The judge also told the experts to alert the court whether it is even possible to test the trace for DNA because previous forensic experts said they believed it was not sufficient.
The DNA on the knife has played a key role in the first two murder trials of Knox, 26, and her ex-boyfriend Raffaele Sollecito, 29.
The pair was originally convicted of the 2007 murder in Perugia partly because forensic experts said they found DNA from Knox and Kercher on a knife in Sollecito's apartment.
In the second trial, the defense successfully challenged the credibility of the finding and raised doubts about whether the knife could have been contaminated by other evidence.
"We are going to examine something we do not even know if it exists" Judge Alessandro Nencini said according to the Italian news agency ANSA. "If it is not found or it has been kept in a way that this test cannot be carried out, the experts must tell us immediately."
If the DNA trace can be tested, a report on the findings must be filed by Oct. 31. The next court hearing is set for Nov. 6.
Knox, who spent four years in an Italian prison, has said she will not return to Italy for the trial. One of her lawyers, Luciano Ghirga, said he exchanges text messages with Knox. He also said he was not worried by the new DNA tests.
"We are certain that they are not organic traces, but just starch cells," Ghirga said.
Sollecito's lawyer said today that Sollecito will appear in court because he wants to make a "spontaneous declaration." In Italian courts, defendants are allowed to make these statements.
The second day of the new trial had a flamboyant moment. Convicted mobster Luciano Aviello was questioned about claims he had made that his brother killed Kercher during a robbery.
Aviello appeared in court wearing women's clothing and said he now wants to be called Lucia. He insisted that his accusation about his brother was true.
A third person, Rudy Guede, has been convicted of the murder and is serving a 16 year prison sentence.