I have no idea if Amanda Knox, convicted of murder by an Italian court in the death of her college roommate, is guilty or not, although I suspect we have not heard the end of the case. (The Italian courts allow for much broader review of criminal cases than their American counterparts, and there are frequent pardons and amnesties, so I wouldn't bet on her serving a full term.) I do know that many comments from American observers have been less than edifying, reflecting numerous misconceptions about Italian law and a generally imperial bias.
My personal favorite is the accusation that the Italian system is "inquisitorial" in nature and provides inadequate protection to defendants. But of course the civil law system is designed to be inquisitorial, in the sense of empowering the judge (magistrate) to seek the truth rather than allow an adversarial process of prosecutors vs. defense attorneys--often severely mismatched in ability and resources--to arrive at a solution or more often a plea bargain arrangement. There are many criticisms of this system, and indeed Italian law in particular has leavened it with several common law-inspired modifications, including limited use of juries and protections for witnesses and defendants unheard of in the traditional civil law (such a jury was indeed used in the Knox case). But I have never heard the criticism that the civil law reaches false conclusions more often than common law courts, much less that Italian courts are harsher than the American version in criminal cases: Knox herself might well be looking at a death sentence in many American states.
A second criticism, made by Alan Dershowitz in a NY Times exchange yesterday, is that Italy lacks a "real" jury system and is inferior to American courts on this basis. (When Dershowitz became an expert on Italian law, I don't know.) But of course, Italy never claimed to have an American-style system: its limited use of juries--actually, judicial panels with a measure of citizen participation--is specifically intended as a hybrid which combines the essence of civil law with the better features, or supposed better features, of the American system. Since another frequent accusation is that people in Perugia are biased against the American students--probably true, on balance--it's hard to see how greater reliance on a jury system would help the defendants, anyway.
A final criticism is that the Italian courts tend to look at a lot of evidence about the defendant's values, behavior, etc. that would not be admissible in an American court. This is mostly true--it reflects a combination of civil law procedure and a sort of Catholic morality that seem alien to American observers--but doesn't necessarily mean the system functions less efficiently. It's flip side is a much greater emphasis on forgiveness and reconciliation as reflected in the absence of the death penalty and other features mentioned above.
There are plenty of things wrong with the Italian judicial system, as even a cursory reading of the newspapers will tell you; and I don't doubt that anti-American prejudice has played a role in the proceedings. (A number of my Italian correspondents have refer to Knox as "Foxy Knoxy" which reflects a somewhat less than open mind to the case.) But I don't think there is reason for a wholesale condemnation of Italian justice or the civil law system, in general. Italy, by the way, repealed its racial (antisemitic) laws in the 1940s. The United States took twenty years longer, and some would say we've never really finished the job.