Prosecutors in Perugia have wound up their eight-month investigation into the murder last November of the British exchange student Meredith Kercher, accusing all three suspects in the case of murder and sexual violence.

Amanda Knox, the American student from Seattle who shared lodgings in Perugia with Ms Kercher; Raffaele Sollecito, her Italian former boyfriend; and Rudy Guede, a Perugia resident and basketball player with joint Italian and Ivory Coast nationality, are all in prison on suspicion of having taken part in the killing. All deny the allegation.

Giuliano Mignini, the prosecutor who led the investigation, has today desposited his findings with Claudia Matteini, the preliminary investigating judge, who will decide within 20 days whether to bring charges.

The three suspects are also accused by prosecutors of "simulating a crime" by allegedly smashing a window to make it appear that there had been a break-in at the whitewashed hillside cottage Ms Kercher shared with Ms Knox and two female Italian students.

Investigators said that the inquiry had been finalised after forensic experts brought in by the judge had given their "definitive conclusions" on evidence found at the scene of the crime. The prosecution reconstruction is that Ms Kercher was forced to her knees and stabbed in the throat after refusing to take part in "a sexual game".

The prosecution report also accuses Ms Knox of falsely implicating Patrick Lumumba Diya, a Congolese musician and bar owner in Perugia, who was arrested but later released and cleared of all suspicion.

Ms Kercher, 21, from Coulsdon, Surrey, was in Perugia to attend the University for Foreigners on an exchange from Leeds University under the European Erasmus programme. Last weekend Ms Knox's parents — Edda Mellas, her mother, and Curt Knox, her father, who are divorced and have both remarried — told The Sunday Times that the handling of the crime scene by investigators had been "shoddy", with evidence such as Ms Kercher's bloodstained bra mishandled.

They challenged police forensic evidence that allegedly shows DNA traces of both Ms Kercher and Ms Knox on a kitchen knife seized at Mr Sollecito's flat, with Ms Knox's trace near the handle and Ms Kercher's at the tip. They also criticised leaks to the Italian media of interrogations, and said a "confession" made by Ms Knox to police late at night had been made under duress and without a lawyer present.

Ms Knox subsequently maintained she had been with Mr Sollecito at his flat on the night of the murder, saying she was "confused" because both she and Mr Sollecito had been high on cannabis.

This week Mr Guede's landlady in Perugia took legal action against him over non payment of 2,365 euros (£1,900) in rent on his flat in Via del Canerino. Nicodemo Gentile, Mr Guede's lawyer, said that Mr Guede was not responsible for keeping up rent payments because the flat had been confiscated and sealed by police after his arrest.

Mr Guede, who fled to Germany after the muder but was intercepted and extradited to Italy, maintains that he and Ms Kercher had "incomplete" consensual sex at the cottage, and that he was in the bathroom with stomach pains when an intruder entered and killed her. He later identified the intruder as Mr Sollecito, and claimed Ms Knox had also been present. Lawyers for both Mr Sollecito and Ms Knox have dismissed this.

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