But Knox, 26, who has expressed concern about returning to a country where she spent four years behind bars, was not in court.
She was convicted in 2009 of murdering Kercher, a 21-year old British exchange student who was found stabbed to death in November 2007 in the villa the two young women rented in the central Italian university town of Perugia.
The convictions of Knox and her ex-boyfriend, Raffaele Sollecito, were overturned in 2011 for "lack of evidence."
After her acquittal, Knox returned to her hometown of Seattle where she has been living since.
But Italy's Supreme Court decided last year to retry the case, saying the jury that acquitted Knox didn't consider all the evidence, and that discrepancies in testimony needed to be answered.
Afraid to go back
Knox has said she's scared to return to Italy.
"I'm afraid to go back there," she said in an interview with CNN's Chris Cuomo in May. "I don't want to go back into prison."
The high court also said evidence could support prosecutors' initial argument -- that Kercher was killed in a twisted sex game gone wrong.
Knox has said such claims are "a bombardment of falsehood and fantasy."
"No one has ever claimed that I was ever taking part in deviant sexual activity. None of my roommates, none of my friends, none of the people who knew me there. This is simply coming out of the prosecution," she told CNN in May. "I was not strapping on leather and bearing a whip. I have never done that. I have never taken part in an orgy. Ever."
The Supreme Court's decision to send the case back to the appeal court for retrial "may be interpreted by the American authorities as double jeopardy -- twice tried for the same fact or the same case," said Riccardo Montana, a law lecturer at City University in London. "In Italy it's not like this, because this is still the same trial."
Watching from afar
If the court convicts her, Knox will be ordered to return to Italy. If she refuses, Italy could request her extradition from the United States. But it's not clear if American authorities would comply.
Knox has said she would be willing to take a lie detector test.
"I'd do anything to prove my innocence," she told CNN affiliate ITV earlier this month. "I don't think that is necessary. But like I said, I'm doing everything to prove my innocence. It's just very sad that's what it has come to."
Knox isn't the only person watching the retrial from afar.
Sollecito, her former boyfriend, told CNN he plans to stay in the Dominican Republic with a friend. At the moment he says he has no immediate plans to return to Italy.
And as the legal saga continues over Kercher's death, her family remains in Britain.
"It took us as a family nearly five years to even begin to feel ready to lay Mez to rest and it is still extremely painful now," they said in a statement Sunday, according to ITV.
They also appeared to respond to recent comments by Knox that she would like to visit Kercher's grave.
"She now has a place near to us that we and her friends can visit to take flowers and spend time...her grave is now her safe place to sleep in peace and be with us and we hope that is respected by all," the family statement said.