Parents of US student at centre of Kercher murder inquiry vow to clear her name

(AP/THE SEATTLE TIMES)

Paying for lawyers and other experts has sunk them deep into debt, "leveraged to the hilt" but the parents of Amanda Knox, the American student accused of murdering British girl Meredith Kercher in Perugia, Italy, say they will "do whatever it takes" to prove her innocent and bring her home.

And Curt Knox and Edda Mellas, who divorced 18 years ago, believe the case against their daughter is already unravelling. In their fullest interview to date, they say the defence will prove the kitchen knife that prosecutors claim killed Kercher could not have caused the fatal wounds, and that traces of the victim's DNA found on its point could match half the population of Italy. The trial is due to begin on 16 September.

Kercher was murdered in the flat that she shared with Ms Knox on 2 November 2007, the night after Halloween. She had had sex – whether consensual or not, it is not clear – with one of the three accused, Herman "Rudy" Guede, a drifter and drug dealer originally from the Ivory Coast, and then, at the climax of a violent struggle, had her throat slashed three times and was left to drown in her own blood.

Mr Guede, also in custody, has admitted having sex with her but denies the murder.

Ms Knox was implicated in the crime after allegedly telling prosecutors that she had been in the kitchen of the flat at the time of the murder and heard her flatmate's screams but merely covered her ears. She blamed the owner of a club in the city, a Congolese musician called Patrick Lumumba, for the murder – though the involvement of Mr Lumumba was first suggested by the prosecutors.

In anonymous leaks to Italian journalists, prosecutors elaborated a lurid picture of the events of the night, claiming that Mr Lumumba, Ms Knox and her Italian student boyfriend, Raffaele Sollecito, all heavily under the influence of cannabis, had been involved in a sex orgy in which Kercher refused to participate.

The story was helped by the fact that Ms Knox kept changing her version, first saying she had spent the night with Mr Sollecito, then telling the police she was at home, then later reverting to the original narrative.

Mr Sollecito's vagueness and contradictory claims about what he had or had not done that evening also damaged their defence. The claims of a Perugia boutique owner that the couple had bought sexy female underwear the night after the killing while Ms Knox yelled about going home and having "wild sex" added to the impression of a couple in the grip of strange emotions.

But in the six months since the investigation began, critical elements in the prosecution's case have fallen away. No evidence was found against Mr Lumumba, who proved that he had been working in his bar that evening. Eventually, he was set free and eliminated from the investigation.

A surveillance video supposedly showing Ms Knox near her home at the time of the murder has been rejected by judges as too grainy. Likewise, her confession about her whereabouts has been excluded because there was no lawyer present. Prosecutors claimed that a kitchen knife found in Mr Sollecito's flat had Kercher's DNA at the tip and Ms Knox's near the handle. Now, according to Ms Knox's parents, the defence is ready to prove that the knife is not compatible with the wounds it is supposed to have caused, and that the DNA said to be Kercher's could belong to half the Italian population.

The only person linked by unequivocal evidence to the murder is Mr Guede, who has admitted having sex with Kercher. He claims he then went to the toilet and was listening to his i-Pod while Mr Sollecito murdered Meredith, which was why he heard nothing. His story has been ridiculed by investigators.

Ms Knox's mother said she was woken before dawn on 2 November – about 1pm in Italy – by a call from her daughter. "She said, 'Mom, I'm OK, I'm home, but I think somebody might have been in my house,'" Ms Mellas told The Seattle Times. "She called again a few hours later, with panic in her voice. Ms Mellas remembers her saying, "They found a body in Meredith's room. I gotta go, the police want to talk to me."

Ms Knox's parents, who say they have got deeply into debt paying lawyers and experts to support their daughter, are clearly deeply unhappy about the way the case has been handled, but choke back their true feelings. "What we can say publicly versus what we really feel are often totally different," said Mr Knox, a vice-president at Macy's department store in Seattle. "We don't have a choice but to believe in their legal system. We will take this as far as we have to, because she is walking out of there totally free."