Perugia, Italy (CNN) -- Murder victim Meredith Kercher's family cannot forgive anyone until they know the truth about her killing, Kercher's sister said Tuesday as Amanda Knox flew out of Italy, a free woman after four years. Knox and her Italian ex-boyfriend Raffaele Sollecito were dramatically cleared of the murder Monday, in a jury ruling that left Knox sobbing and almost unable to walk out of the court unaided. The decision stunned the Kercher family, who were visibly downcast Tuesday morning. It sends them "back to square one," Kercher's brother Lyle said. Stephanie Kercher, the victim's sister, demurred when asked if the family is ready to forgive Meredith's killer or killers.
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NEW: Knox is emotional, "overwhelmed" after arriving in Seattle
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The exoneration of Knox and her ex-boyfriend sends the victim's family "back to square one"
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The Kercher family cannot forgive anyone "until the truth is known," the victim's sister says
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Knox and Raffaele Sollecito successfully appealed their convictions of murder
A third person, drifter @placeholder, was convicted separately of involvement in the killing and is serving 16 years.