Knox spoke at the end of a trial that has exposed some of the most intimate details of her life, with prosecutors depicting her as a promiscuous and manipulative she-devil who brutally murdered her British roommate in Perugia, Meredith Kercher.
The trial, in which Knox's ex-boyfriend Raffaele Sollecito figures as a co-defendant, is wrapping up after almost a year. Thursday's session was devoted to rebuttals by defense lawyers and the prosecution, and the eight members of the jury are expected to begin deliberations as early as Friday.
Standing up, her voice breaking as she fought back tears, the 22-year-old American told the court that she feels "vulnerable" and fears losing herself after two years in jail.
"I have written on a piece of paper ... that I was afraid of losing myself," she said, speaking Italian. "I am scared of being branded what I am not," she said. "I am scared of having the mask of an assassin forced onto me."
Knox and Sollecito, an Italian, are charged with murder and sexual assault in the 2007 slaying. Prosecutors are seeking life sentences, while both defendants are pleading innocent. Any verdict can be appealed by both parties.
Both Knox, a 22-year-old student from Seattle, and Sollecito, 25, have been jailed since shortly after the slaying.
The brutal murder has made headlines worldwide, bringing the lives of the defendants under the spotlight. Sordid details of sex and drugs have been dug by the media that have descended on this university town as much as discussed in court.
The jury, which includes two judges, is not sequestered.
During the trial, about a hundred witnesses have taken the stand in the frescoed rooms just steps away from the medieval fountain that is a symbol of the town: relatives of the victim described Kercher's love of Italy, her friends spoke of the last hours before she died, acquaintances described the relations between the two women.
Knox herself has taken the witness stand, giving a composed testimony months ago during which she called the victim a friend and offered her alibi, saying she spent the night at Sollecito's house where the two watched a video.
According to the prosecution, Kercher and Knox had different personalities - the victim a serious student; the alleged murderer a promiscuous youth of dubious hygiene - and had grown apart so much that Knox wanted to get back at her for being "smug."
The prosecutors contend that on the night of the murder, Nov. 1, 2007, Knox and Sollecito met at the apartment where Kercher and Knox lived. They say a fourth person was there, Rudy Hermann Guede, an Ivory Coast citizen who has been convicted in the murder and sentenced to 30 years in prison. Guede, who is appealing his conviction, maintains he was in the house the night of the murder but did not kill Kercher.
The prosecution says that Knox and Kercher started arguing and the three brutally attacked and sexually assaulted the Briton. They were acting, according to the prosecution, under "the fumes of drugs and possibly alcohol."
Kercher's body, her throat slit, was found in a pool of blood the next day at the apartment.
Francesco Maresca, a lawyer representing Kercher's family, argued in his rebuttals Thursday that the Briton was killed because she knew her murderers and would be a threat to them if she survived.
"Meredith died because after she was attacked, threatened, wounded, and after a violent sexual approach, they needed her to remain silent," he said.
Knox says Kercher was a friend whose death shocked her. Defense lawyers have described her as a smart, cheerful woman, at one point even comparing her to film character Amelie, the innocent and dreamy girl in the 2001 French movie of the same title. That is the film Knox and Sollecito say they were watching on his computer the night of the murder.
Sollecito, also addressing the court Thursday, insisted that no motive had emerged to explain his alleged role in the slaying. He disputed the prosecution's view that he was submissive toward Amanda and had been manipulated by her.
"Not having found a motive to explain why I would kill, they said I was a sort of dog on a leash," he said. "If Amanda had asked me to do something I didn't agree with, I would have said no. Let alone if she had asked me to do something as terrible as killing a girl."
DNA traces that the prosecutors have linked to the defendants have been disputed in court. The defense lawyers contend that traces are either two small to be attributed with certainty or that evidence may have been inadvertently contaminated.
The prosecution maintains that a a 6 1/2-inch (16.5-centimeter) knife they found at Sollecito's house could be the murder weapon. The knife has Kercher's DNA on the blade and Knox's on the handle, they say.
But defense lawyers argue that the knife is too big to match Kercher's wounds and that the amount of what prosecutors say is Kercher's DNA is too low to be attributed with certainty.
The defense has largely focused on the lack of evidence and what they say is the absence of a clear motive.
Escorted by prison guards, Knox looked tense as she came to the courtroom, where one of the prosecutors, Manuela Comodi was opening the day's proceedings with another appeal to the court to convict the two defendants.
"She's hanging in there," Knox's mother, Edda Mellas, told CBS "Early Show" co-anchor Harry Smith. "I mean she knows she's innocent, but here she's been locked up for two years for a crime she didn't commit, even though she is innocent. So you know, she is scared."
"We all are hopeful and we trust these judges and the jury to know that they are going to not put two innocent kids in jail for a crime that they didn't commit," Mellas told reporters after the hearing.
Knox has given contradicting versions, saying at one point that she was home the night of the murder and had heard Kercher's screams and accusing a Congolese man of the killing. The man, Patrick Diya Lumumba, owns a pub in Perugia where Knox worked. He was jailed briefly but was later cleared and is seeking defamation damages from Knox.
Knox said police pressure led her to initially accuse an innocent man.
A verdict is expected Friday or Saturday, and Kercher's family is expected to be in court.