"If you want to speak at the trial, come to the trial," said appeal court judge Alessandro Nancini before reading out her email in the courtroom in Florence.
Knox has been in the United States ever since an appeal court acquitted her in 2011 over the 2007 killing of British student Meredith Kercher, a ruling that was overturned by the supreme court earlier this year.
"I am not present at the hearing because I am afraid. I am afraid that the vehemence of my accusers you will leave an impression on you, that their smoke in the eyes will blind you," Knox's email was quoted as saying.
"I am not a monster," she said. She said Kercher, her housemate and alleged victim, was "a friend".
"I liked her, she helped me, she was generous and funny, I never criticized enough," she said, following accusations from prosecutors that a deep rift between the two was the basic motive for the murder.
Referring to a partial confession that she made to investigators in the days after the murder, Knox said that she had been "tortured psychologically".
"They lied to me, shouted at me, threatened me, hit me on the head twice. They told me I would never see my family again if I did not remember what happened."
Prosecutors have asked for a 30-year prison sentence for Knox and 26 years for her ex-boyfriend Raffaele Sollecito, arguing her punishment should be harsher because she initially accused someone else of the crime.
Kercher, an exchange student from London, was found half-naked in a pool of blood with multiple stab wounds on November 2nd 2007 in the house she shared with Knox in the university town of Perugia in central Italy.
Knox and Sollecito, who have both protested their innocence, served four years in prison for the murder.
Rudy Guede, a local petty thief and drug dealer, has been convicted separately and is serving a 16-year sentence for the gruesome murder with no appeal.
Prosecutors say the DNA evidence, which is highly disputed in the case, showed that Sollecito and Knox had stabbed Kercher while Guede sexually assaulted her.
A verdict in the case is expected next month. If they are convicted, Knox and Sollecito can still appeal to the supreme court and the chance of Knox being extradited from the United States is extremely remote.
Sollecito has attended two trial hearings but has been spending most of his time in the Dominican Republic.