Nicola Sacco and Bartolomeo Vanzetti were convicted and executed for shooting and killing a payroll guard, Alessandro Berardelli, during a robbery that took place in South Braintree, Massachusetts on April 15, 1920. Berardelli and another payroll guard, Frederick Parmenter, were supposed to take a total of over $15,000 in two iron boxes from one factory of the Slater and Morril shoe factory to the second Slater and Morril factory in South Braintree. During their route, they passed two men leaning against a piperail fence and, as they passed, were attacked from behind by these two men. Berardelli was shot four times and Parmenter two times. After this, the two men picked up the iron boxes containing the money and fled, along with three other men, in a black touring car which had approached the scene of the crime. Berardelli died about an hour later, Parmenter succumbed to his wounds the following morning.
Sacco and Vanzetti were known members of an anarchist movement in the US. The investigators knew that members of an anarchist group were involved in the robbery, and following a series of events, Sacco and Vanzetti were arrested on May 5. After a long trial with many witnesses, they were found guilty of the shooting of Berardelli while performing a criminal act, the robbery. An appeals process was launched and the Governor of Massachusetts launched his own investigation of the case. The committee entitled with this investigation also found Sacco and Vanzetti guilty as charged. Final appeals to the Supreme Court did not have any effect, and on August 23, 1927, Sacco and Vanzetti were executed.
Numerous books and articles have been written on this case by experts from fields including law, history and social sciences, since many felt that the case was probably one of the worst miscarriages of justice in American legal history. Studies of, for example, Young and Kaiser (1985) have introduced new evidence never introduced at the trial. Kadane & Schum (1996) carried a thorough probabilistic analysis of the case. The below description is based on Kadane & Schum, further adapted by Bex et al. (2003)
The main conclusion is that Sacco was at the scene of the robbery when it occurred. The prosecution had two witnesses. Lewis Pelser testified that he saw Sacco at the scene of the robbery and the shootings from the window of the Rice and Hutchins factory. Lewis Wade testified that he saw someone who looked like Sacco at the scene of the crime, which, according to the prosecution, implied that Sacco was at the scene of the crime.
A defence witness called Albert Frantello testified that Sacco was not one of the men leaning against the fence when he passed it five minutes before the robbery occurred. The defence argued from this that Sacco could thus not have been at the scene of the crime when the robbery took place. The reasoning from Frantello's testimony was strengthened by the fact that, according to Frantello, the man on the fence spoke “American” while, as observable during trial, Sacco spoke broken English. The prosecution argued that Frantello's powers of observation were weak since at cross-examination he incorrectly identified characteristics of jurors he had been asked to view, and thus his testimony carried less weight.
Further defence witnesses were brought forth to cast doubt upon whether Pelser could have actually seen the robbery. McCullum testified that Pelser could not have seen the shooting for reasons not further specified. Constantino testified that Pelser was under a bench when the shootings took place, and thus Pelser could not have seen the shooting. On cross-examination, however, Constantino had doubts about his observation. Pelser nevertheless admitted that he was under the bench on cross-examination. Brenner testified that Pelser was not near the window so that he could not have seen the robbery. At his cross-examination, Brenner also expressed doubts about where Pelser was.