MILAN, Italy - The nation's highest court this week takes up the Amanda Knox case for the second time as a parallel trial-by-social media rages online, with partisans on both sides seeking to shape public opinion over a murder case that has polarized observers in three nations.

While the Internet advocacy and sparring over the Knox trial details - on blogs, forums, and most vociferously on Twitter - have no bearing on the real court case, observers and participants say it does have a role in shaping public opinion, particularly in the United States, where the exchanges are most acerbic.

And public opinion could eventually have some bearing, if a confirmed guilty verdict requires Knox to serve a sentence and Italy seeks to extradite her.

"This has become their life, and both sides are desperate to win any way they can. Even if that is in the court of public opinion, they will take that win," said Laurie Levenson, a law professor who directs the center for legal advocacy at Loyola Law School. "Everyone has woken up and realized that the law is not etched in stone. It is in the eye of the beholder and they are trying to influence that."

The Italian Court of Cassation on Wednesday is expected to rule on Knox's and her former Italian boyfriend Raffaele Sollecito's appeals to their guilty verdicts in British student Meredith Kercher's 2007 killing, issued last year by a Florence appeals court that sentenced Knox to 281/2 years and Sollecito to 25 years.

Both had been found guilty by a trial court in Perugia, then freed after a Perugia appellate court overturned the convictions, only to find themselves back in an appellate court after the high court vacated the acquittals in a harsh rebuke of the Perugia chief appellate judge's reasoning.

Knox, who spent four years in jail during the investigation and after her lower court conviction, remains free in the United States. She has vowed never to return willingly to Italy. If her conviction is upheld now or in future decisions, any decision on her extradition will include a political component that could, in some part, be swayed by public opinion.

"She would need a groundswell of support to at least stave off the [U.S.] government from moving forward" on any extradition request from Italy, said Levenson.