The American flatmate of Meredith Kercher heard the British exchange student’s dying screams, but insists that she played no part in her death.

Amanda Knox, 20, told detectives that she covered her ears to shut out the screams and thuds made after Patrick Diya Lumumba, a Congolese immigrant, went into Ms Kercher’s room at the whitewashed house she shared with Ms Kercher and two Italian girls, Italian newspapers reported.

Police believe that Ms Kercher, 21, from Coulsdon, South London, was killed after she refused to have sex with Mr Lumumba, Ms Knox and Ms Knox’s Italian boyfriend, Raffaele Sollecito, 24. The three are suspected of conspiring to commit manslaughter and sexual violence. They are being held in isolation cells in a prison in Capanne, outside Perugia, and will be questioned by a judge today.

Police were reportedly last night examining a flick knife which they found at Mr Sollecito’s home, checking it for blood and fingerprints.

Italian newspapers carried extensive accounts of the testimonies of Ms Knox and Mr Sollecito. Officers said that both had given “confused and partial” statements that were “full of holes”. Mr Lumumba, who has a Polish wife, Alessandra, and a two-year-old son, shouted: “It wasn’t me,” as he was arrested.

Last night Italian news sources reported that Ms Knox, of Seattle, had “crumbled” after police intercepted a mobile phone call to her boyfriend in which she said: “Raffaele, I can’t do this any more, I can’t keep this up.” They took this to mean that her previous evidence had not been truthful.

Pathologists’ reports suggest that two people were involved in the killing, with one holding Ms Kercher down while the other “sexually violated” her. When asked if she had held Ms Kercher down, Ms Knox “burst into tears and went into a state of shock”, Italian reports said.

Mr Sollecito claimed that he was not present on the evening of the murder, but police said that a footprint found in a pool of blood in Ms Kercher’s bedroom could be his. They said that Ms Kercher had died between midnight and 2am last Friday.

A police report to be presented to the investigating judge today is expected to accuse Ms Knox of lying in her statement and forcing Mr Sollecito to give her a “false alibi”.

Mr Sollecito initially told police that Ms Knox was with him on the night of the murder. He later admitted that this was untrue and said that he had spent the evening alone in his flat and that Ms Knox had returned to spend the night with him from about 1am.

Police believe that all three suspects were present at the time of the murder, although Mr Sollecito told them he received a phone call at his home from his father Franco at 11.30pm, which his father confirmed.

Ms Knox made her “confession” to police when she was taken in for questioning at dawn yesterday. She had claimed earlier to have left the cottage at 5pm on Thursday and returned only the next morning when Ms Kercher’s body was discovered. She now admits that she was at the house. She said that on the evening of November 1 she had met Mr Lumumba, who owned the Le Chic pub where she sometimes worked, at about 9pm after they had exchanged texts. She told police they had gone to the cottage. “I don’t remember if my friend Meredith was already there or whether she came later. What I can say is that [Meredith and Patrick] went off together.”

She added that she and Mr Lumumba had told Ms Kercher they wanted to “have some fun”. “Patrick wanted her [Ms Kercher], and he had her,” she said. “Patrick and Meredith went off together into Meredith’s room while I think I stayed in the kitchen. I can’t remember how long they were in the bedroom together, I can only say that at a certain point I heard Meredith screaming and I was so frightened I put my fingers in my ears.” She claimed she had had a lot to drink and had fallen asleep.

She added: “I’m not sure whether Raffaele was there too that evening but I do remember waking up at his house in his bed and that in the morning I went back to where I lived, where I found the door open.” Police said that Mr Sollecito had continued to claim he was not present on the evening of the murder. In his testimony he said he and Ms Knox went into town until 8.30pm or 9pm, when he returned home.

“I don’t remember what we did,” he said. “Amanda told me she was going to the Le Chic pub to meet friends.”

He said that he had gone home, “smoked a joint”, eaten dinner and then spoken to his father on the phone. After surfing the internet for a couple of hours he went to bed. Ms Knox had returned at around 1am. He said that Ms Knox rose at 10am the next morning, before leaving to go to the cottage to change her clothes before she returning and saying that she had seen blood there. The pair went to investigate.

He claimed his previous statement had been “rubbish” because he had “believed Amanda’s version of what happened”. He did not “think about the inconsistencies”.

Ms Kercher’s family laid a red rose on the steps of Perugia Cathedral. A note with the flower bore the inscription: “Love you forever, Meredith. All my love, Dad.” More than 100 students gathered in Leeds last night to remember Ms Kercher during an emotional vigil at the University of Leeds. The students walked together slowly from the Parkinson steps to the Tetley Garden where Ms Kercher’s photograph was lit by candles under a tree.

A university spokesman described Ms Kercher as a “beautiful, clever and happy young woman”.

Times Recommends

• Would you live on the wrong side of the Berlin Wall?
• Wish you were here, says Iraq tourist board
• Russian policeman’s corruption plea to Putin