The "Red Scare" following the First World War and the Bolshevik Revolution was used by elements in the Justice Department (in particular a young J. Edgar Hoover) to bolster their careers. The two principals in the case were Italian immigrants and had been opposed to the war, and in fact fled to Mexico to avoid the draft. The facts that they were immigrants, draft-dodgers, and attended meetings of supposedly "Red" political groups were all strikes against them in the minds of the average American citizen of the period.
The two did not have what could be termed perfect command of the English language, and obviously suffered confusion during the trial because of that. The evidence for and against the two is itemized in one of the links below. The fact that the witnesses for their alibis were all Italian immigrants weighed heavily against the accused, another example of the post-war isolationism of America. Since many were also involved in "anarchist" politics, this also played into the hands of the prosecutors. The entire episode is a rather sad example of American justice at one of its low points. An ironic note is that although the trial and surrounding publicity was very biased, the truth is that one of the men was guilty, and the other apparently involved to some degree.
In 1977 Massachusetts Governor Michael Dukakis issued a proclamation absolving the two men, who had been executed 50 years earlier. Although a popular move, this may not have been wise, since evidence subsequent to their executions indicates that while Vanzetti was innocent Nicola Sacco was guilty. In 1943 Carlo Tresca, the anarchist leader originally chosen as their lawyer, claimed that to be the case. Others involved in their defense also stated that Vanzetti was innocent of "actual participation" in the crime, but may have been involved in some way, but that Sacco was guilty in all respects.
The fear of Communism "infecting" America in the wake of the Bolshevik Revolution demonstrated how civil liberties suffers in the times of social unrest. Emerging from World War I, convinced of the supposedly evil nature of Communism, America as a nation and society was not at the point of embracing discourse and discussion. The actions of the United States government towards Communist Russia only heightened this sensibility. In refusing the diplomatically recognize actively seek to undermine the Communist nation, the political expression of fear and negation was mirrored by its society. The overwhelming fear of anarchists and Communists played into the false accusations of Sacco and Vanzetti. Little actual evidence was presented at the trial. The prosecution's case rested on the immigrant status of both, as well as their supposed political leanings of being anarchists. Historical record finds little proof that either wrote or actively voiced the dismembering of the American government. Banking on public fear and hysteria, both were sentenced and executed. Since both government and society mirrored one another, it seems that both elements were feeding one another, fanning the proverbial flames of intolerance. The fact that Sacco and Vanzetti were different, and might have believed in different elements of social and political notions of the good demonstrates that in a climate of fear and confusion, civil liberties and rights based discourse is one of the first elements to be discarded.
The Sacco-Vanzetti case revealed the whole anatomy of American life with all its classes, professions, and points of view and all their relations, and it raised almost every fundamental question of our political and social system. - Edmund Wilson
There was a hostile bias that was demonstrated by authorities in this case. The two Italian men had many strong supporting alibis and witnesses who were all Italian as well with poor English skills. They were found guilty by an unconvinced all-American jury during the worst and most intense political repression in history. Sacco and Vanzetti, who had no prior criminal records, were caught in a trap set by police for a friend of theirs who was a foreign-born radical. The men were deemed guilty by association and because they lied when being questioned about their radical activities they created a "consciousness of guilt". Although these activities had nothing to do with the Braintree murders authorities had their minds already made up. This case is considered the greatest in political trial history and demonstrates with flying colors how civil rights liberties suffer during social unrest.