Amanda Knox joins her Italian trial via email

American student Amanda Knox pleaded her innocence in the murder of her roommate Meredith Kercher in an email to an Italian court on Tuesday, saying she was afraid to appear in person for fear of conviction.

The case has dragged on for six years, frustrating attempts by the British student's family to discover the truth about her death, and with three trials doing little to clear up mysteries surrounding the details of the murder.

"I am innocent. I did not kill, I did not rape, I did not steal, I did not plot or instigate. I did not kill Meredith, I did not take part in her murder," the lengthy letter written in Italian said, read to the court by her lawyer Luciano Ghirga in closing arguments for the defense.

Kercher's half-naked body was found with more than 40 stab wounds and a deep gash in her throat in the apartment she shared with Knox in Perugia, a picturesque town where both were studying as university exchange students.

Knox explained the unusual step of defending herself in an email rather than in person by saying she feared lawyers for the Kercher family would succeed in their request to have her sentenced to three decades in prison.

"I am not present in court because I am scared. I fear that the prosecution's line will influence the decision and will blind everyone," read the email, sent from the United States where Knox now lives.

The student, 26, and her Italian former boyfriend Raffaele Sollecito, 29, were convicted of murdering Kercher in 2009, in a verdict overturned in a subsequent trial.

SLANDER CONVICTION

Now the case is being tried again in a courtroom in Florence after Italy's Supreme Court quashed the acquittals in March, citing inconsistencies in the case. Sollecito pleaded his innocence in an address to the court last month in which he described the charges as "absurd".

Ivory Coast-born Rudy Guede is serving a 16-year sentence for the 2007 murder, but the prosecution says the wounds of the 21-year-old Leeds University student indicate there was more than one attacker.

Knox, who has a standing conviction for slander for falsely implicating Congolese bar owner Patrick Lumumba in the crime, wrote in the letter that she made the accusation under pressure from police.

Francesco Maresca, the lawyer representing the Kercher family, dismissed her arguments as well-worn. The prosecution insists forensic evidence proves without doubt that Knox and Sollecito are guilty of the crime.

"Letters from those involved in the trial I'd take with a pinch of salt," Maresca told Reuters outside court in response to Knox's email.

A final verdict in the retrial is expected in mid-January.

That verdict would then need to be confirmed by the high court to become official, a process that would take months, and it is unclear whether the United States would agree to extradite Knox to serve any eventual sentence.

Knox has appealed against her slander conviction to the European Court of Human Rights, which has binding power over Italy, and could do the same if convicted of the murder.

The email concluded: "I am innocent. Raffaele is innocent. Meredith and her family deserve the truth. I ask you to put an end to this enormous injustice. In faith, Amanda Marie Knox." (Writing by Naomi O'Leary; Editing by Alison Williams)