An American accused in the 2007 killing of a British student in Italy is expected to defend herself from charges of murder and sexual assault when she takes the stand Friday.

Amanda Knox, an exchange student from Seattle, is on trial in the central Italian town of Perugia for the death of her roommate and fellow student, 21-year-old Meredith Kercher.

Knox and co-defendant Raffaele Sollecito, her former Italian boyfriend, have always denied wrongdoing.

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"She's a bit nervous about going on to the stand, but she's also quite confident in what she has to say and that the truth will come out during her testimony," the American's father, Kurt Knox, told CBS' "Early Show" on Thursday.

"She is going to be telling the truth and answering all of the questions, and hopefully the court will see that and see that she had nothing to do with this and that she's 100 percent innocent," Knox said, speaking from Perugia.

He said that during the testimony his daughter would be speaking Italian, which she mostly learned during the year and a half she has spent in jail.

Kercher was found in a pool of blood in the apartment she shared with Knox on Nov. 2, 2007. Prosecutors allege the defendants strangled and stabbed her neck and say the Briton was killed during what began as a sex game.

Kercher's wounds were compatible with a kitchen knife the prosecution says might have been the murder weapon. The knife was found at Sollecito's house and prosecutors say Knox's DNA was found on the handle and Kercher's was found on the blade.

Knox and Sollecito, jailed since shortly after the slaying, have given conflicting statements over their whereabouts the night of the murder.

Knox initially said she was at home and implicated the Congolese owner of a bar where she worked. The man was cleared after being detained for two weeks, and Knox has since insisted she was not at home during the slaying.

Sollecito has said he was at his own apartment in Perugia, working at his computer. He said he does not remember if Knox spent the whole night with him or just part of it.

The two risk Italy's stiffest punishment, life imprisonment, if convicted of murder.

A third suspect in the case, Ivory Coast national Rudy Hermann Guede, was found guilty of murder and sexual violence and was sentenced to 30 years in prison. He was given a fast-track trial at his request, and his appeal is set to start in November. He too denies wrongdoing.