Well, with an innocent verdict, it follows that they tried to fit Knox up. Should they be tried? In a perfect world, yes, actually - getting people imprisoned for four years for murders they didn't commit ruins peoples lives. In this case, just the act of interviewing her for a crime she didn't commit has made a convicted criminal of her. In reality, I think a safe conviction would be impossible and if you start trying cops/prosecutors every time there's a not guilty verdict, you undermine the whole justice system, so clearly not practical.