Chilling new evidence in the investigation into whether American student Amanda Knox took part in the murder of her college roommate indicates that more than one person was involved in what the court described as a "ferocious" assault.
Newly filed court papers in Perugia, Italy, obtained by ABCNEWS.com, cite a neighbor who heard bloodcurdling screams the night of the Nov. 1 murder, followed by the sound of footsteps from several people running away.
The papers were filed this week by a three-judge panel to keep Ivory Coast native Rudy Hermann Guede in jail on suspicion of murder. The court had previously ruled that Knox and her boyfriend Raffale Sollecito were also to remain behind bars while the investigation continued.
The body of Meredith Kercher, a 21-year-old British exchange student, was found in her bedroom Nov. 2 with her throat slashed.
Knox, Kercher's 20-year-old roommate from Seattle, was quickly arrested along with Sollecito, 23. Guede, 21, was arrested and extradited from Germany earlier this month.
Knox and Sollecito have claimed they were not in the house at the time of the murder, but in an 18-page court document regarding Guede, the judges summarize the evidence so far, noting that it confirms "the presence of more than one person in that house at the time Meredith was killed."
A key piece of evidence is testimony by a neighbor who said she heard terrible screaming come from the house on via della Pergola on the night of the murder. The neighbor told police she also heard the sound of hurried footsteps from a number of people running from the house "right after the tragic ending of the evening."
This is confirmation, the judges wrote, of "a group participation in the ferocious criminal act, that cannot be considered in passive terms for any of those present."
The judges have earlier concluded that Knox and Sollecito took part in the murder, with Guede's role still to be established.
Guede is the only suspect who admits to being at the scene of the crime, but denies any involvement in the murder. He claims he saw and scuffled with the killer and tried to rescue Kercher, but then ran off because he was scared.
Guede was denied release from jail on the grounds that his testimony was riddled with false statements, "which prevent it from being considered even a minimal or partial account of what happened." The document states that Guede's account is an "awkward attempt of an explanation" for the evidence that puts Guede on the scene of the crime.
Other evidence that the prosecutor claims has implicated the trio:
A bloody handprint found on a pillow under the victim and DNA evidence found in the bathroom of the house and on Kercher's body belonged to Guede.
A bloody shoe print on the scene of the crime matched Sollecito's shoe.
A knife found in Sollecito's house contained DNA from Knox on the handle and from the victim on the blade.
Knox's blood was found on the sink in one of the bathrooms, and the absence of her fingerprints in the house where she lived (except for a single print on a glass) was evidence that she was there and carefully cleaned up traces of her presence.
Knox has said that she was with Sollecito at his house for the entire night of Nov. 1, but Sollecito's proof that he, too was home — his use of the computer that night — has been dismantled by police.
The panel of three judges, presided over by Andrea Battistacci, remains baffled for a motive in the grisly attack.
Battistacci wrote that the "incredible and ferocious" murder came out of the atmosphere of the meeting of many new people that is typical of university life. Yet the judge is clearly taken aback by the violence "because it is instinctively inacceptable that young people of the same age who are also acquaintances of the victim, could take their thoughtlessness to such an extreme as to commits such a cruel crime without their being a strong conflict or an extreme state of alteration."
The suspicion of investigators and judges who have ruled on this case so far is that the murder was the result of a sexual assault gone wrong.
On Tuesday, investigators returned to the house where Kercher was killed to gather more evidence and removed various objects from the house for tests.
A fourth suspect, "Patrick" Diya Lumumba, 44, is still under investigation, but no longer in jail. He was released because the prosecutor decided he did not have enough evidence to justify his continued jail custody.
With additional reporting from Perugia by Carla Rumor