Kercher murder: the three versions

Amanda Knox, the American flatmate of the murdered British student Meredith Kercher, has for the first time been implicated as being at the scene of the crime by her former Italian boyfriend.

With a verdict imminent in the pre-trial hearings over the murder in Perugia almost a year ago, the three suspects in the case appear to have turned on each other.

After the conclusion of the hearings, Judge Paolo Micheli, 44, a former Carabinieri officer who has been a magistrate since 1990, will decide tomorrow whether Ms Knox and Raffaele Sollecito, her former boyfriend, should stand trial for the murder.

At the same time, he is also due to convict or clear Rudy Guede, the Ivory Coast immigrant who is accused by prosecutors of taking part in the killing, but who has opted for a fast track trial in the hope of a reduced sentence if found guilty.

Lawyers for Mr Sollecito have told the judge that, according to a forensic expert called by the defence, Ms Knox's DNA is on Ms Kercher's bloodied bra-strap as well as that of Mr Sollecito and Rudy Guede.

Professor Francesco Vinci, the forensic scientist, said the DNA traces were "too contaminated" to be useable as evidence, but showed the presence of "at least three people".

The admission appears to support the prosecution case that all three were present at the scene of the crime.

It also breaks a tacit pact between Ms Knox and Mr Sollecito, who have sent each other supportive letters while in custody and until now have avoided incriminating each other. Mr Sollecito even sent Ms Knox flowers on her birthday this summer.

Lawyers for both Mr Sollecito and Ms Knox have repeatedly claimed the couple spent the night of the murder at Mr Sollecito's flat, indicating that Mr Guede was the lone killer.

Today, the prosecution and defence lawyers will present their closing arguments. They will argue that if a trial date is set, the suspects should be released from prison into house arrest. Ms Knox has asked to be housed at San Fatucchio, a supervised community and farm in the Umbrian countryside, 40 kilometres from Perugia, for recovering drug addicts and young offenders run by the Catholic charity Caritas.

Last weekend Walter Biscotti, one of Mr Guede's lawyers, accused Ms Knox and Mr Sollecito of framing his client, a drifter and small-time drug dealer who was brought up in Perugia and mingled with the student community. "We believe Knox and Sollecito were the murderes," Nicodemo Gentile, another of Mr Guede's lawyers said.

Mr Biscotti said Mr Guede, the only one of the three who admits he was at the hillside cottage Ms Knox shared with Ms Kercher on the evening of the murder, admitted attempting to have consensual sex with Ms Kercher, but had not raped or killed her. The prosecution says that Mr Guede's DNA was on Ms Kercher's bloodstained pillow.

Ms Kercher was found last November semi-naked in her bedroom with her throat cut. The prosecution claims she was assaulted just after Hallo'een in a murderous sex game, possibly inspired by a Japanese comic strip about vampires which Mr Sollecito had been reading.

Prosecutors say that Ms Knox stabbed her flatmate while the other two forced her to her knees and held her down, with Mr Sollecito pinning her by the arms and Mr Guede holding her by the throat.

Ms Knox's lawyers reject this, saying Ms Kercher was assaulted by "one robust killer". Last week, Ms Knox burst into tears when the allegation was made in court that she stabbed Ms Kercher, saying: "Meredith was my friend, I had no reason to kill her."

Mr Guede claims he was listening to his iPod in the bathroom when Ms Kercher was killed in the bedroom. He fled to Germany after the killing, but was tracked down three weeks later in Germany.

Mr Sollecito's defence team, headed by Giulia Bongiorno, a high profile lawyer and parliamentary deputy, brought props including a shop window mannequin wearing a bra into court last week to back their case. They claim "a thief", who they suggest was Mr Guede, smashed a window to enter the cottage, killed Ms Kercher when she returned and recognised him, and fled with her two mobile phones, later found in a nearby garden.

Ms Bongiorno argued that the presence of Mr Sollecito's DNA on the bra fastener but not the rest of the garment proved it was due to contamination and mishandling by police forensic scientists.

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