Investigators said on Friday they had identified the weapon believed to have been used in the brutal murder of a 22-year-old English exchange student here and that it belonged to one of the suspects in custody.
The body of Meredith Kercher was found last Friday with her throat slashed in the house she shared with three other girls on the outskirts of this central Italian city.
Police on Tuesday arrested Kercher's 20-year-old American roommate, Amanda Marie Knox; the roommate's 24-year-old Italian boyfriend, Raffaele Sollecito; and 38-year-old Lumumba Diya, also known as Patrick, from the Democratic Republic of the Congo.
In a report released to the press, police said they had concluded that Kercher was killed with a knife belonging to Sollecito, "which he always had with him".
However, they added, it was still not possible to determine who wielded the fatal blow.
Based on evidence from the autopsy, police said Kercher was apparently threatened with the knife, suffering two minor cuts before "the threat turned into something much more serious" with the third, fatal blow.
The autopsy also showed that while the victim had signs of sexual abuse, no seminal fluids were found in her body.
According to investigators, the three suspects may have been "seeking new sensations" or fulfilling some sexual fantasy. And they may also have been under the influence of drugs.
This would explain why so much evidence was left at the scene of the crime, police observed.
In their report, investigators did not rule out that a fourth person may have been involved, based on the discovery of an unidentified fingerprint on the victim's bloodied cushion.
Based on the investigators report, a judge on Friday confirmed the arrests and ordered that the three suspects remain in custody. Both Sollecito and Diya have denied any involvement in the murder, while Knox has stopped answering investigators' questions.
Earlier this week she told police she had seen Diya go into Kercher's bedroom and later heard her scream.
Sollecito maintains he was never in the apartment at the time of the murder, after initially telling police he was there in order to corroborate Knox's story.
However, a bloody shoe print found in the apartment is compatible with the university student's Nike sneakers. Diya claims to have an alibi for the time the murder took place. He told investigators he had been at the night club where he works and that there were cash register receipts and witnesses to prove this. Kercher, a student at the university of Leeds, arrived in Perugia in August to take part in the European Union's Erasmus university exchange programme, while Knox was studying Italian at the University for Foreigners.
