SEATTLE - Amanda Knox and her family said they're not worried about a decision by Italian prosecutors to appeal her acquittal on charges of killing her roommate in 2007.

Knox was on a University of Washington program to study in Perugia when her British roommate Meredith Kercher was killed. She and her ex-boyfriend Raffaele Sollecito, served four years in prison before an appeals court overturned their convictions.

"The appeal of Amanda's acquittal by the prosecution was not unexpected as they had indicated from the day of the verdict that they would appeal. We are not concerned about this appeal as Amanda's innocence was clearly and convincingly proven in her appeal trial. This is simply another example of harassment by the prosecution against Amanda and makes this terrible, painful incident continue to go on for Amanda, Raffaele and their families," the family said in the statement released Tuesday by spokesman David Marriott.

Her U.S. lawyer, Theodore Simon, also was not surprised by the appeal.

"While the prosecution, as expected, has appealed, very little has changed. The appellate jurors conducted a thorough, painstaking, searching inquiry into the true facts and determined in a lengthy, logical and comprehensive decision, that Amanda Knox was not guilty of the tragic loss of Meredith Kercher," Simon said in a statement.

Knox returned to Seattle last year after her release from custody.