With her voice breaking, Knox addressed the eight members of the jury Thursday, just before they were scheduled to begin their deliberations, possibly Friday. It was her final statement to the court.
Knox said she was afraid she was losing herself, frightened of being branded "what I am not."
"I am scared of having the mask of an assassin forced onto me," she told the court, speaking Italian.
Knox is charged with murder and sexual assault in the slaying of Meredith Kercher, a 21-year-old who was studying in Perugia. Also on trial is Knox's boyfriend at the time of the slaying, Italian Raffaele Sollecito. All three were students in Perugia.
Prosecutors are seeking life sentences. Both defendants have pleaded innocent. The verdict can be appealed by both parties.
Thursday's session was devoted to the rebuttals by both defense lawyers and the prosecution.
In her remarks, Knox said she was trying to remain calm even though she is "disappointed, sad and frustrated" over her two years in jail. She said she remained "confident and certain in what I know."
Knox thanked her family and friends who supported her. She also thanked the prosecutors who seek to put her behind bars for life, saying they were only seeking justice.
"They are trying to do their job, even if they can't understand," she said.
Both Knox, a 22-year-old student from Seattle, and Sollecito, 25, have been jailed since shortly after the slaying.
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, too - Ivory Coast citizen Rudy Hermann Guede.
Guede has been convicted of murder and sexual assault in separate proceedings, and been sentenced to 30 years in prison. He has appealed his conviction, saying he was in the house the night of the murder but did not kill Kercher.
According to the prosecution, Kercher and Knox started arguing and then the three brutally attacked the Briton and sexually assaulted her. They were acting, according to the prosecutors, under "the fumes of drugs and possibly alcohol."
The defense has focused largely on the lack of evidence and what they say is the absence of a clear motive.
Knox's lawyer, Carlo Dalla Vedova, said in his closing arguments days ago that "there are still many doubts in this trial." He said the DNA evidence cannot be attributed "beyond any doubt."