Italian prosecutors yesterday summed up their case against American exchange student Amanda Knox in the 2007 murder of her British housemate Meredith Kercher citing "irrefutable" scientific evidence.

DNA and other forensic evidence linking 22-year-old Knox to the gruesome crime in the central Italian university town of Perugia is "irrefutable and well corroborated," said deputy prosecutor Manuela Comodi.

As the trial of Knox and co-defendant Raffaele Sollecito, her boyfriend at the time, was drawing to a close, prosecutors were expected to request life in prison for the American student and her former boyfriend accused of killing the young British woman in Italy.

Amanda Knox and Raffaele Sollecito are charged with murder and sexual violence in the 2007 slaying of Knox's roommate in Perugia. They deny wrongdoing.

In her closing remarks yesterday, prosecutor Manuela Comodi said evidence presented during the trial had shown that the defendants' cell phones were switched off the night of the crime, making their whereabouts impossible to trace. Comodi also recalled testimony by expert witnesses who said Sollecito's computer had not been used during the hours Kercher was stabbed to death.

According to Knox, who took the stand last June, the two suspects went to Sollecito's place to watch a movie on his computer on 1 November and spent the night there, smoking pot and having sex.

The Briton's body was found on the morning of 2 November in the apartment she shared with Knox.

The 21-year-old woman is believed to have died between 9pm and 11pm on 1 November, based on the autopsy and the accounts of friends with whom she had eaten dinner that night, according to court documents.

Prosecutors were due to make the sentencing requests later yesterday. A verdict is expected in early December.

Prosecutors argued Friday that Kercher was killed during a drug-fuelled sex game. They said Knox had a growing hatred for the victim and killed her, together with Sollecito and a third man, under "the fumes of drugs and possibly alcohol".

During his seven-hour closing speech, prosecutor Guilano Mignini said Kercher died about 11:30pm after she and Knox had quarreled – either over money or Guede's presence at the house.

The prosecutor said the men pinned Kercher down by her arms while Knox played with the knife, prodding at her throat and saying: "Ah, you were pretending to be such a little saint.... Now we are going to show you."

Knox's lawyer, Carlos Della Vedova, later told reporters, "I believe that Mignini's presentation was very suggestive, but we are in a courtroom, and proof is needed in order to convict a person."

Mignini defended his investigation, saying the criticism came from journalists, detectives, bloggers and lawyers from Italy and abroad who were seeking fame. He said police and prosecutors handled the case professionally, adding that it was time to bring the saga to a close.

Francesco Maresca, a lawyer for the Kercher family, said he was "very satisfied" with the prosecutor's argument, adding that the crimes should bring a life sentence.

Knox appeared drained as she sat in court.

Rudy Hermann Guede from Ivory Coast was sentenced to 30 years in prison last year for the killing. He is appealing his conviction.