Simply put, an accused person who is found not guilty cannot be tried again for the same crime. Not so in Italy. Witness the six-year long travail of Amanda Knox. In their first trial, Ms. Knox and her former boyfriend, Raffaele Sollecito, were convicted of murder. Later they were acquitted by an appellate court. In the United States that would have ended the case. There are no appeals of acquittals here. Not so, in Italy.
The acquittal was appealed to even a higher court. Ms. Knox did not appear at that trial, understandably, after having spent four years in prison before she was acquitted, and fearing she might once again be found guilty. The new court in Florence retried the case before a jury of two judges and six lay jurors; that jury gave its verdict on January 30th after deliberating less than a day. Guilty!
This case illustrates the wisdom of our founders in guaranteeing finality, in that nobody can be retried for a crime, after that person has once been acquitted of that crime. Double jeopardy in the United States is more than a quiz show. It is a fundamental right of Americans accused of crime.