She was initially convicted despite the fact that there was no actual evidence against her. Nor did she have a believable motive. Being an American was apparently enough. An appeals court overturned her conviction, and she came home. But apparently Italy has one of those bizarre legal systems in which the prosecution can appeal the overturning of a conviction, and even an acquittal!
I recently read former FBI profiler John Douglas's new book, in which he details his investigation of the case, his reasons for being absolutely convinced that Knox is innocent, and the degree to which the Italian judicial system has made itself a laughingstock over the case already.
But apparently they aren't through. And it's inexcusable that this innocent young woman should have to once again face a charge that was baseless to begin with.