Knox and her co-defendant, Raffaele Sollecito of Italy, are charged with murder and sexual assault in the 2007 slaying of Meredith Kercher. The three were all studying in Perugia and Knox and Sollecito were dating at the time.
The prosecutors are seeking a life sentence for both, including nine months of daytime solitary confinement for Knox and two months for Sollecito. Both defendants say they are innocent. Any verdict can be appealed by both parties.
Just a day before the deliberations began, Knox made an emotional appeal, trying for the last time to convince the court that she is not a murderer.
Standing up, her voice breaking as she fought back tears, the 22-year-old American told the court that she feels "vulnerable" 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."
Both Knox, who is from Seattle, and Sollecito, 25, have been jailed since shortly after the slaying. They were taken to their cells as they awaited the ruling.
Italian law allows for suspects in serious crimes to be jailed even before indictment, if they are considered a flight risk among other reasons.
If convicted, Knox is likely to remain in jail, even though in Italy sentences are not served until all appeals are exhausted, a process that can take years. Under Italian law, in case of a guilty verdict, she can receive a lesser sentence than the one requested by the prosecutors.
If acquitted, Knox would go back to prison for some paperwork before leaving, her family said. They declined to give details on any travel plans to go back to the United States.
The prosecutors contend 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, says he was in the house the night of the murder but did not kill Kercher.
The prosecution says 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.
The prosecutors have described Knox as a manipulative, sexually promiscuous woman whose personality clashed with her roommate's. They say Knox had grown to hate Kercher and wanted to get back at her.
Knox says Kercher was a friend whose death shocked her. Defense lawyers have described the American as a smart and cheerful woman.
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 in the police investigation.
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.
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.
Knox and Sollecito are also being tried on lesser charges, including staging a break-in, carrying a knife, and the theft of about euro300 ( or about $450) in cash and Kercher's cell phones and credit cards. Prosecutors say Knox and Sollecito broke a window in a bedroom to stage a burglary and sidetrack the investigation.
Kercher's family is expected to be in court for the verdict.