The American wrote in the letter submitted to the appeal court in Florence by her lawyers before their closing arguments: “I didn’t kill Meredith.”
She added: “I am not in court because I am afraid” that prosecutors would “blind” the court to her innocence.
Presiding Judge Alessandro Nencini read into the record the email, written in Italian, noting that it was highly unusual given Knox’s absence.
Ms Kercher, 21, of Coulsdon, Surrey, was killed in the apartment she shared with Knox in the university town of Perugia. Her throat had been cut and her body left beneath a blanket in her bedroom. Prosecutors claim Knox and her then boyfriend, Raffaele Sollecito, carried out the murder with a third man, Ivory Coast-born Rudy Guede, who is serving a 16-year sentence.
The case is being tried for a third time after Italy’s highest court annulled a 2011 appellate court ruling throwing out their initial murder convictions. The high court’s scathing opinion tore apart the lower court’s decision to free the pair as full of errors and contradictions.
Knox, now 26, spent four years in prison until she was freed in 2011 and returned to the United States, where she remains. Sollecito, 29, has attended several hearings of the current appeal. Defendants in Italy are not required to attend trials.
Knox said in the email: “I am not in court because I am afraid. I am afraid that the vehemence of the prosecution will make an impression on you, that their smoke will get in your eyes and blind you.
“I am not afraid of your powers of discernment, but because the prosecution has succeeded already in convincing a court comprised of responsible and perceptive adults to convict innocent people, Raffaele and me.”
She said she was following the case closely “given that my life is at stake”.
And she wrote: “I didn’t kill. I didn’t rape. I didn’t rob. I didn’t plot. I didn’t instigate. I didn’t kill Meredith.”
Meredith Kercher, 21, was murdered in November 2007 in the apartment she shared with Knox in the picturesque Italian university town of Perugia. She had been raped and stabbed dozens of times.
Knox declared her innocence in Ms Kercher’s death, saying the two were friends without any conflicts between them.
She also said had no contact with Rudy Guede, a small-time drug-dealer who is serving a 16-year sentence for Ms Kercher’s murder.
Prosecutors claim Knox and Sollecito carried out the murder with Guede, whose conviction specifies that he did not act alone.
Prosecutors are seeking a 26-year sentence against both Knox and Sollecito for the murder, and an additional year added to Knox’s three-year slander conviction – which stands – for wrongly accusing a bar owner of the murder.
Prosecutors say the slander amounts to an aggravating circumstance, claiming that Knox lied to deflect investigators’ attention from her.
Knox, in the email, said she falsely accused bar owner Patrick Lumumba under pressure from the Italian police, who made her sign a false confession “that made no sense and should not have been considered legitimate evidence”.
She said she was denied a lawyer during 50 hours of interrogation over four days in Italian, a language she said she barely knew at the time. “They lied to me, yelled at me, threatened me, and gave me two slaps on the head,” she wrote.
A verdict in the trial is expected in mid-January.