Ferdinando Nicola Sacco (April 22, 1891 - August 23, 1927) and Bartolomeo Vanzetti (June 11, 1888 - August 23, 1927) were anarchists who were convicted of murdering two men during a 1920 armed robbery in Massachusetts. After a controversial trial and a series of appeals, the two Italian immigrants were executed on August 23, 1927.

There is highly politicized dispute over their guilt or innocence, as well as whether or not the trials were fair. The dispute focuses on small details and contradictory evidence, and historians have not, as of 2010, reached consensus. Sacco and Vanzetti were accused of the murders of Frederick Parmenter, a paymaster, and Alessandro Berardelli, a security guard, at the Slater-Morrill Shoe Company, on Pearl Street in Braintree, Massachusetts, during the afternoon of April 15, 1920. Vanzetti was further charged with the theft of $15,776.51 from the company. Police suspicions regarding the Braintree robbery-murder and an earlier attempted robbery in Bridgewater, Massachusetts, centered on local Italian anarchists. While neither Sacco nor Vanzetti had a criminal record, the authorities knew them as radical militants and adherents of Luigi Galleani. Police speculated about a connection between the crimes and the recent activities of the Galleanist anarchist movement, thinking that the robberies were made to gain funds for a bombing campaign. The two men were arrested in Brockton, Massachusetts, on May 5, 1920, after appearing at a garage to pick up a car that police believed was used in the robberies. Both had pistols on them, along with anarchist literature, and Vanzetti was carrying shotgun shells similar to those used in the holdups. Vanzetti was first tried for the armed robbery in Bridgewater and convicted. Both men were then tried for the Braintree crimes and convicted. After several failed appeals over six years, Sacco and Vanzetti were executed in the electric chair on August 23, 1927. Celestino Medeiros, who had confessed to the murders, was executed the same day.

Sacco was a shoe-maker born in Torremaggiore, Foggia, who emigrated to the United States at the age of seventeen. Vanzetti was a fishmonger born in Villafalletto, Cuneo, who arrived in the United States at age twenty. Both men left Italy for the U.S. in 1908, although they did not meet until a 1917 strike. The men were followers of Luigi Galleani, an Italian anarchist who advocated revolutionary violence, including bombing and assassination. Galleani published Cronaca Sovversiva (Subversive Chronicle), a periodical that advocated violent revolution, and an explicit bomb-making manual called La Salute è in voi!. At the time, Italian anarchists ranked at the top of the United States government's list of dangerous enemies. Since 1914, they had been identified as suspects in several violent bombings and assassination attempts, including an attempted mass poisoning. Publication of Cronaca Sovversiva was suppressed in July 1918, and the government deported Galleani and eight of his closest associates on June 24, 1919.

Remaining Galleanists either sought to avoid arrest by becoming inactive or going underground, or remained active. For three years, perhaps 60 Galleanists waged an intermittent campaign of violence against US politicians, judges, and other federal and local officials, especially those who had supported deportation of alien radicals. Among the dozen or more violent acts was the bombing of US Attorney General A. Mitchell Palmer's home on June 2, 1919. In that incident, one Galleanist, Carlo Valdonoci, a former editor of Cronaca Sovversiva and an associate of Sacco and Vanzetti, was killed. The bomb intended for Attorney General Palmer exploded in Valdonoci's hands. Radical pamphlets entitled "Plain Words" signed "The Anarchist Fighters" were found at the scene of this and several other midnight bombings that night.

Several Galleanist associates were suspected or interrogated about their roles in the bombing incidents. Two days before Sacco and Vanzetti were arrested, a Galleanist named Andrea Salsedo fell to his death from the Justice Department's Bureau of Investigation offices on 15 Park Row in New York City. People speculated that Salsedo may have been pushed out the window or dropped as he was held by his ankles during interrogation, a well-known "third-degree" technique. Roberto Elia, another Galleanist under arrest, was later deposed in the inquiry. He testified that Salsedo had committed suicide for fear of betraying the others. Salsedo worked in the Canzani Printshop in Brooklyn, where federal agents traced the "Plain Words" leaflet. The Galleanists knew that Salsedo had been held, and reportedly beaten, for two months, which led to rumors that Salsedo and his comrade Roberto Elia had made important disclosures concerning the bomb plot of June 2. The rumors about the confessions were later confirmed by Attorney General Palmer to encourage fear. The Galleanist plotters realized that they would have to go underground and dispose of any incriminating evidence. Sacco and Vanzetti were found to have correspondence with several Galleanists; one letter warned Sacco to destroy all mail after reading.

On April 16, one day after the robbery-murders, the Federal Immigration Service called local police chief Michael E. Stewart to discuss Galleanist anarchist Ferruccio Coacci, whom he had arrested on their behalf two years earlier. Coacci had succeeded in postponing his deportation until April 15, 1920, the day of the Braintree holdup. The FIS asked Stewart to investigate Coacci's excuse that he had failed to report for deportation because his wife had fallen ill. Stewart sent two policemen to Coacci's house on April 16. They found Coacci's wife in good health. Coacci insisted on being arrested for immediate deportation. As he had an alibi for the robbery: his time card showed he was at work on April 15, he was deported on April 18. Suspicious, Stewart returned to the Coacci residence on April 20, where he found "Mike Boda" (an alias of Mario Buda, the chief Galleanist bombmaker) renting the house. Buda volunteered that Coacci's wife had left in a hurry. Under questioning, Buda admitted owning a .32 caliber Spanish automatic pistol and possessing a diagram of a Savage automatic, such as the one used in the murders. Buda said he owned a 1914 Oakland, which was being repaired. Police thought two cars had been kept at the now empty Coacci garage, and believed a Buick and smaller car were used during the holdup. When Stewart discovered that Coacci had worked for both the plants that had been robbed, he returned with the Bridgewater police, but Buda had disappeared, along with his possessions and furniture.

The police had instructed the Johnson garage, where the impounded cars were held, to notify them when the owners came to collect the 1914 Oakland. On May 5, 1920 Buda arrived at the garage with three other men, later identified as Sacco, Vanzetti and Riccardo Orciani. Police were alerted but the men sensed a trap and fled. Buda escaped on a motorcycle with Orciani. He later resurfaced in Italy in 1928. Tracked onto a streetcar, Sacco and Vanzetti were soon arrested. Vanzetti claimed that the revolver he was carrying was for protection. To avoid deportation, the pair denied being allied with anarchists. A postcript to the arrests occurred in 1926, when a bomb destroyed the house of Samuel Johnson, the brother of the Simon Johnson who had called police the night of Sacco and Vanzetti's arrest.

Following the indictment of Sacco and Vanzetti, anarchists in other countries began violent retaliation. In 1921, a booby trap bomb mailed to the American ambassador in Paris exploded, wounding his valet. Other bombs sent to American embassies were defused.

Only Vanzetti was tried for the attempted robbery and attempted murder in Bridgewater. Others arrested produced ironclad alibis, like Sacco's time-card proving he was at work. In 1927, advocates for Sacco and Vanzetti charged that this case was brought first because evidence against Vanzetti in the Braintree robbery was weak and a conviction for the Bridgewater crimes would help convict him for the Braintree crimes. The prosecution countered that the timing was driven by the schedules of different courts that handled the cases.

On the recommendation of supporters, Vanzetti chose to be represented by John P. Vahey, an experienced defense attorney, rather than accept counsel appointed by the court. Frederick Katzmann, Norfolk and Plymouth County District Attorney, prosecuted the case. The presiding judge was Webster Thayer, who was already assigned to the court before this case was scheduled. A few weeks earlier he had given a speech to new American citizens decrying Bolshevism and anarchism's threat to American institutions. He supported the suppression of radical speech.

The trial began on June 22, 1920. The prosecution presented several witnesses who put Vanzetti at the scene of the attempted robbery. Their descriptions varied, especially with respect to the shape and length of Vanzetti’s mustache. Physical evidence included a shotgun shell retrieved at the scene of the crime and several shells found on Vanzetti when he was arrested. The defense produced sixteen witnesses — all Italians from Plymouth who claimed they had bought eels for the Christmas holiday from him in accordance with their Christmas traditions. Such details reinforced the difference between the Italians and the Yankee jurors. Some testified in imperfect English, others through an interpreter whose failure to speak the same dialect of Italian as the witnesses hampered their effectiveness. On cross examination, the prosecution found it easy to make the witnesses appear confused about dates. A boy who testified admitted rehearsing his testimony. "You learned it just like a piece at school?," the prosecutor asked. "Sure," he replied. The defense tried to rebut the eyewitnesses with testimony that Vanzetti always wore his mustache in a distinctive long style, but the prosecution rebutted their testimony.

Though the defense case went badly, Vanzetti did not testify in his own defense. Vanzetti, in 1927, said his lawyers opposed putting him on the stand. That same year, Vahey told the governor that Vanzetti had refused his advice to testify. A lawyer who assisted Vahey in the defense, decades later, said that the defense attorneys left the choice to Vanzetti but warned that it would be difficult to prevent the prosecution from using cross examination to impeach his character based on his political beliefs and that Vanzetti chose not to testify after consulting with Sacco. Herbert Ehrmann, who later joined the defense team, wrote many years later that the dangers of putting Vanzetti on the stand were very real. Another legal analysis of the case concluded that the defense would have little to lose from Vanzetti's testimony, since his conviction looked certain given how poorly his alibi witnesses had performed under cross. That analysis deemed the defense overall "unconvincing" and "not closely argued or vigorously fought."

On July 1, 1920, the jury deliberated for five hours and returned guilty verdicts on both counts, attempted robbery and attempted murder. Before sentencing, Thayer learned that during deliberations the jury had tampered with the shells found on Vanzetti at the time of his arrest to determine if the shot they contained was of sufficient size to kill a man. Since that prejudiced the jury's verdict on the attempted murder charge, Thayer ignored that conviction. On August 16, 1920, he sentenced Vanzetti for attempted robbery to a term of 12 to 15 years in prison, the maximum sentence allowed. An assessment of Thayer’s conduct of the trial, while critical — "his stupid rulings as to the admissibility of conversations are about equally divided" — found little in the record to demonstrate partiality. The defense raised only minor objections in an appeal that was not accepted. A few years later, Vahey joined Katzmann’s law firm.

Later Sacco and Vanzetti both stood trial for murder in Dedham, Massachusetts, for the South Braintree killings, with Webster Thayer again presiding. He had asked to be assigned the trial. Well aware of the Galleanists' reputation for constructing dynamite bombs of extraordinary power, Massachusetts authorities took great pains to defend against a possible bombing attack. Workers outfitted the Dedham courtroom where the trial was to be held with cast-iron bomb shutters (painted to match the wooden ones fitted elsewhere in the building) and heavy, sliding steel doors that could protect that section of the courthouse from blast effect in the event of a bomb attack. Each day during the trial, Sacco and Vanzetti were escorted in and out of the courtroom under a heavy armed guard.

Vanzetti again claimed that he had been selling fish at the time of the Braintree robbery. Sacco claimed that he had been in Boston in order to gain a passport from the Italian consulate. He had claimed to have had lunch in Boston's North end with several friends, each of whom testified on his behalf. Prior to the trial, Sacco's lawyer, Fred Moore, went to great lengths to contact the consulate employee Sacco said he had talked with on the afternoon of the crime. Moore's friend found the man back in Italy. The clerk said he remembered Sacco because of the unusually large passport photo he presented. The clerk also remembered the date — April 15, 1920. Moore's friend tried to get the clerk to return to America to testify but the clerk, in ill health, refused. What could have been key alibi testimony by a reputable clerk was reduced to a sworn deposition read aloud in court and quickly questioned by the prosecution, which claimed Sacco's visit to the consulate could not be established with certainty. The prosecution also pointed out that Sacco's dinner companions were fellow anarchists.

Much of the trial focused on material evidence, notably bullets, guns, and a cap. Prosecution witnesses testified that the .32-caliber bullet that had killed Berardelli was of a brand so obsolete that the only bullets similar to it that anyone could locate to make comparisons were those in Sacco's pockets. Yet ballistics evidence, which was presented in exhaustive detail, was equivocal. Prosecutor Frederick Katzmann, after initially promising he would not try to link any fatal bullet with Sacco's gun, changed his mind after the defense arranged test firings of the gun. Sacco, claiming he had nothing to hide, had allowed his gun to be test-fired, with experts for both sides present, during the trial's second week. The prosecution then matched bullets fired through the gun to those taken from one of the slain guards. In court, two prosecution experts swore that one of the fatal bullets, quickly labeled Bullet III, matched one of those test-fired. Two defense experts said the bullet did not match. Years later, defense lawyers would suggest that the fatal bullet had been substituted by the prosecution. Noting that witnesses swore to seeing one gunman pump bullets into Berardelli, they asked how only one of four bullets found in the deceased could have come from Sacco's gun.

Even more doubt surrounded Vanzetti's gun. Since all of the bullets found at the scene were .32 caliber and Vanzetti's gun was .38 caliber, there was no direct evidence tying Vanzetti's gun to the crime scene. The prosecution claimed it had originally belonged to the slain guard and that it had been stolen during the robbery. No one testified to seeing anyone take the gun, but the guard, while carrying $15,776.51 in cash through the street, had no gun on him when found dead. The prosecution traced the gun to a Boston repair shop where the guard had dropped it off a few weeks before the murder. The defense, however, was able to raise doubts, noting that the repair shop had no record of the gun ever being picked up and that the guard's widow had told a friend that he might not have been killed had he claimed his gun. Still, the jury believed this link as well.

The prosecution's final piece of material evidence was a flop-eared cap claimed to have been Sacco's. Sacco tried the cap on in court and, according to two newspaper sketch artists who ran cartoons the next day, it was too small, sitting high on his head. But Katzmann insisted the cap fitted Sacco and continued to refer to it as his.

Further controversy clouded the prosecution witnesses who identified Sacco at the scene of the crime. One, a bookkeeper named Mary Splaine, precisely described Sacco as the man she saw firing from the getaway car. Yet cross examination revealed that Splaine had refused to identify Sacco at the inquest and had seen the getaway car for only a second and from nearly a half-block away. While a few others singled out Sacco or Vanzetti as the men they had seen at the scene of the crime, far more witnesses, both prosecution and defense, refused to identify them.

After deliberating for only three hours, then breaking for dinner, the jury returned with a guilty verdict. Supporters later insisted Sacco and Vanzetti had been convicted for their anarchist views, yet every juror insisted anarchism had played no part in their decision. First degree murder in Massachusetts was a capital crime. Sacco and Vanzetti were therefore bound for the electric chair unless the defense could find new evidence.

The verdicts and the likelihood of death sentences immediately roused international opinion. There were demonstrations in 60 Italian cities and a flood of mail to the American embassy in Paris. Demonstrations followed in a number of Latin American cities. Anatole France, veteran of the campaign for Alfred Dreyfus and recipient of the 1921 Nobel Prize for Literature, wrote an "Appeal to the American People": "The death of Sacco and Vanzetti will make martyrs of them and cover you with shame. You are a great people. You ought to be a just people."

While the prosecution staunchly defended the verdict, the defense, led by radical attorney Fred Moore, continued to develop evidence that raised doubts. Three key prosecution witnesses stated that they had been coerced into identifying Sacco at the scene of the crime, but when confronted by District Attorney Katzmann they denied any coercion. One of them, Lola Andrews, a nurse, told authorities that she was forced to sign an affidavit stating she had wrongfully identified Sacco and Vanzetti. She signed a counter affidavit the following day. Another, Lewis Pelser, described how he had submitted to alleged prosecutorial coercion while drunk and signed a counter affidavit shortly thereafter.

In 1924, controversy continued when it was discovered that someone had switched the barrel of Sacco's gun with that of another Colt automatic used for comparison. Other appeals focused on the jury foreman and a prosecution ballistics expert. In 1923, the defense filed an affidavit from a friend of the jury foreman who swore that prior to the trial, the man had said of Sacco and Vanzetti, "Damn them, they ought to hang them anyway!" That same year, a state police captain retracted his trial testimony linking Sacco's gun to the fatal bullet. Captain William Proctor claimed that he never meant to imply the connection and had repeatedly told Katzmann there was no such connection, but that the prosecution had crafted its trial questioning to disguise his true assessment.

The conduct of trial judge Webster Thayer also buttressed calls for a new trial. During the trial, many had noted how Thayer seemed to loathe defense attorney Fred Moore. Thayer frequently denied Moore's motions, lecturing the California-based lawyer on how law was conducted in Massachusetts. Once Thayer told reporters that "No long-haired anarchist from California can run this court!" According to the sworn affidavits of eyewitnesses, Thayer also lectured members of his clubs, calling Sacco and Vanzetti "Bolsheviki!" and saying he would "get them good and proper". Following the verdict, Boston Globe reporter Frank Sibley, who had covered the trial, wrote a protest to the Massachusetts attorney general condemning Thayer's blatant bias. The New York World attacked Thayer as "an agitated little man looking for publicity and utterly impervious to the ethical standards one has the right to expect of a man presiding in a capital case." Thayer denied all motions for a new trial on October 1, 1924. That same year, Thayer confronted a Massachusetts lawyer at his alma mater Dartmouth. "Did you see what I did with those anarchistic bastards the other day. I guess that will hold them for a while ... Let them go to the Supreme Court now and see what they can get out of them.", the judge said. His words were not disclosed until 1927.

The defense appealed Thayer's denial of their motions to the Supreme Judicial Court (SJC), the highest level of the state's judicial system. Both sides presented arguments to its 5 judges on January 11–13, 1926. The SJC returned a unanimous verdict upholding Judge Thayer's decisions on May 12, 1926. The Court did not have the authority to review the trial record as a whole or to judge the fairness of the case. Instead, the judges only considered whether Thayer had not abused his discretion in the course of the trial. Thayer later claimed that the SJC had "approved" the verdicts, which advocates for the defendants protested as a misinterpretation of the Court's ruling, which only found "no error" in his individual rulings.

In November 1925, Celestino Medeiros, an ex-convict awaiting trial for murder, confessed to committing the Braintree crimes. He absolved Sacco and Vanzetti of participation. In May, once the SJC had denied their appeal and Medeiros was convicted, the defense investigated the details of Medeiros’ story. Police interviews led them to the Morelli gang based in Providence, Rhode Island. They developed an alternative theory of the crime based on the gang’s history of shoe-factory robberies, connections to a car like that used in Braintree, and other details. Gang leader Joe Morelli bore a striking resemblance to Sacco.

The defense filed a motion for a new trial based on the Medeiros confession on My 26, 1926. In support of their motion they included 64 affidavits. The prosecution countered with 26 affidavits. When Thayer heard arguments on September 13–17, 1926, the defense, along with their Medeiros-Morelli theory of the crime, charged that the U.S. Justice Department was aiding the prosecution by withholding information obtained in its own investigation of the case. Attorney William Thompson made an explicitly political attack: "A government which has come to value its own secrets more than it does the lives of its citizens has become a tyranny, whether you call it a republic, a monarchy, or anything else!" Judge Thayer denied this motion for a new trial on October 23, 1926. After arguing against the credibility of Medeiros, he addressed the defense claims against the federal government, saying the defense was suffering from "a new type of disease,... a belief in the existence of something which in fact and truth has no such existence."

Three days later, the Boston Herald responded to Thayer's decision by reversing its longstanding position and calling for a new trial. Its editorial, "We Submit", earned its author a Pulitzer Prize. No other newspapers followed suit.

The defense promptly appealed once more to the Supreme Judicial Court and presented their arguments on January 27–28, 1927.

While the judges were considering this appeal, Harvard law professor and future Supreme Court Justice Felix Frankfurter published an article in the Atlantic Monthly arguing for a retrial. He noted that the SJC had already taken a very narrow view of its authority when considering the first appeal and called upon the court to review the entire record of the case. He called their attention to Thayer's lengthy statement that accompanied his denial of the Medeiros appeal, describing it as "a farrago of misquotations, misrepresentations, suppressions, and mutilations," "honeycombed with demonstrable errors."

The Supreme Judicial Court denied the Medeiros appeal on April 5, 1927. Summarizing the decision, the New York Times said that the SJC had determined that "the judge had a right to rule as he did" but that the SJC "did not deny the validity of the new evidence."

Many famous socialists and intellectuals campaigned for a retrial without success. John Dos Passos came to Boston to cover the case as a journalist, stayed to author a pamphlet called Facing the Chair, and was arrested in a demonstration on August 10, 1927, along with Dorothy Parker. After being arrested while picketing the State House, Edna St. Vincent Millay pleaded her case to the governor in person and then wrote an appeal: "I cry to you with a million voices: answer our doubt... There is need in Massachusetts of a great man tonight." Others who wrote to Fuller or signed petitions included Albert Einstein, George Bernard Shaw and H. G. Wells. The president of the American Federation of Labor cited "the long period of time intervening between the commission of the crime and the final decision of the Court" as well as "the mental and physical anguish which Sacco and Vanzetti must have undergone during the past seven years" in a telegram to the governor. Benito Mussolini, himself the target of two anarchist assassination attempts, quietly made inquiries through diplomatic channels and was prepared to ask Governor Fuller to commute the sentences if it appeared his request would be granted.

For their part, Sacco and Vanzetti seemed to alternate between moods of defiance, vengeance, resignation, and despair. The June 1926 issue of Protesta Umana published by their Defense Committee carried an article signed by Sacco and Vanzetti that appealed for retaliation by their colleagues. In the article, Vanzetti stated "I will try to see Thayer death [sic] before his pronunciation of our sentence" and asked fellow anarchists for "revenge, revenge in our names and the names of our living and dead." In a reference to Luigi Galleani's bomb-making manual (covertly titled La Salute è in voi!), the article concluded "Remember, La Salute è in voi!". Both Sacco and Vanzetti wrote dozens of letters sincerely expressing their innocence. Sacco, in his awkward prose, and Vanzetti in his eloquent but flawed English, insisted they had been framed because they were anarchists.

On April 9, 1927, Judge Thayer heard final statements from Sacco and Vanzetti. In a lengthy speech Vanzetti said:

I would not wish to a dog or to a snake, to the most low and misfortunate creature of the earth – I would not wish to any of them what I have had to suffer for things that I am not guilty of. But my conviction is that I have suffered for things that I am guilty of. I am suffering because I am a radical and indeed I am a radical; I have suffered because I am an Italian and indeed I am an Italian... if you could execute me two times, and if I could be reborn two other times, I would live again to do what I have done already.

Thayer declared that the responsibility for the conviction rested sole with the jury's determination of guilt. "The Court has absolutely nothing to do with that question." He sentenced each of them to "suffer the punishment of death by the passage of as current of electricity through your body" during the week beginning July 10. He twice postponed the execution date while the governor considered requests for clemency.

On May 10, a package bomb addressed to Governor Fuller was intercepted in the Boston post office.

In response to public protests that greeted the sentencing, Massachusetts Governor Alvan T. Fuller faced last minute appeals to grant clemency to Sacco and Vanzetti. On June 1, 1927, he appointed an Advisory Committee of three: President Abbott Lawrence Lowell of Harvard, President Samuel Wesley Stratton of MIT, and Probate Judge Robert Grant. They were tasked with reviewing the trial to determine whether it had been fair. Lowell's appointment was generally well received, for though he had controversy in his past he had also at times demonstrated an independent streak. The defense attorneys considered resigning when they determined that the Committee was biased against the defendants, but some of the defendants' most prominent supporters, including Harvard Law Professor Felix Frankfurter and Judge Julian W. Mack of the U.S. Circuit Court of Appeals, persuaded them to stay because Lowell "was not entirely hopeless." One of the defense attorneys, though ultimately very critical of the Committee's work, thought the Committee members were not really capable of the task the Governor set for them: "No member of the Committee had the essential sophistication that comes with experience in the trial of criminal cases.... The high positions in the community held by the members of the Committee obscured the fact that they were not really qualified to perform the difficult task assigned to them." He also thought that the Committee, particularly Lowell, imagined it could use its fresh and more powerful analytical abilities to outperform the works of those who had worked on the case for years, even finding evidence of guilt that professional prosecutors had discarded.

Grant was another establishment figure, a probate court judge from 1893 to 1923 and an Overseer of Harvard University from 1896 to 1921, and the author of a dozen popular novels. Some criticized Grant's appointment to the Committee, with one defense lawyer saying he "had a black-tie class concept of life around him," but Harold Laski in a conversation at the time found him "moderate." Others cited evidence of xenophobia in some of his novels, references to "riff-raff" and a variety of racial slurs. His biographer allows that he was "not a good choice," not a legal scholar, and handicapped by age. Stratton, the one member who was not a Boston Brahmin, maintained the lowest public profile of the three and hardly spoke during its hearings.

After two weeks of hearing witnesses and reviewing evidence, the trio determined that the trial had been fair and a new trial was not warranted. They assessed the charges against Thayer as well. Their criticism, using words provided by Judge Grant, would hardly sound harsh to those outside the legal profession: "He ought not to have talked about the case off the bench, and doing so was a grave breach of judicial decorum." But they also found some of the charges about his statements unbelievable or exaggerated, and they determined that anything he might have said had no impact on the trial. The panel's reading of the trial transcript convinced them that Thayer "tried to be scrupulously fair." The Committee also reported that the trial jurors were almost unanimous in praising Thayer’s conduct of the trial.

A defense attorney later noted ruefully that the release of the Committee's report "abruptly stilled the burgeoning doubts among the leaders of opinion in New England." Supporters of the convicted men denounced the Committee. Harold Laski said the decision represented Lowell's "loyalty to his class."

On August 15, 1927, with the executions scheduled for midnight on the 22nd, a bomb exploded at the home of one of the Dedham jurors. On Sunday, the 21st, more than 20,000 protesters assembled on Boston Common.

Both Sacco and Vanzetti refused a priest several times on their last day. Their attorney William Thomson asked Vanzetti to make a statement opposing violent retaliation for his death and they discussed forgiving one's enemies. Celestino Medeiros, whose execution had been delayed in case his testimony was required at another trial of Sacco and Vanzetti, was executed first. Sacco was next and went quietly to the chair, then shouted "Viva l'anarchia!" and "Farewell, mia madre." Vanzetti, in his final moments, shook hands with guards and thanked them for their kind treatment, read a statement proclaiming his innocence, and finally said, "I wish to forgive some people for what they are now doing to me."

Violent demonstrations swept through many cities the next day, including Geneva, London, Paris, Amsterdam, and Tokyo. In South America wildcat strikes closed factories. Three died in Germany, and protesters in Johannesburg burned an American flag outside the American embassy.

At the funeral parlor in Boston's North End, more than 10,000 mourners viewed Sacco and Vanzetti in open caskets over two days. On Sunday, August 28, a two-hour funeral procession bearing huge floral tributes moved through the city. Police blocked the route, which passed the State House, and at one point mourners and the police clashed. The hearses reached Forest Hills Cemetery where, after a brief eulogy, the bodies were cremated. The Boston Globe called it "one of the most tremendous funerals of modern times." Will H. Hays, head of the motion picture industry's umbrella organization, ordered all film of the funeral procession destroyed.

Sacco's ashes are in Torremaggiore, the town of his birth, at the base of a monument erected in 1998. Vanzetti's ashes were buried with his mother in Villafalletto.

A few days after the executions, Sacco's widow thanked Italian anarchist Severino Di Giovanni by letter for his support and added that the director of the tobacco firm Combinados had offered to produce a cigarette brand named "Sacco & Vanzetti". On November 26, 1927, Di Giovanni and his comrades bombed a Combinados tobacco shop shortly afterwards. Di Giovanni, one of the most vocal supporters of Sacco and Vanzetti in Argentina, bombed the American embassy in Buenos Aires a few hours after Sacco and Vanzetti were condemned to death. On December 24, 1927, Di Giovanni blew up the headquarters of the Citibank and of the Bank of Boston in Buenos Aires in apparent protest of the execution. In December 1928, Di Giovanni and his comrades failed in an attempt to bomb the train in which President Herbert Hoover traveled during his visit to Argentina.

Three months later, bombs exploded in the New York subway, in a Philadelphia church, and at the home of the mayor of Baltimore. One of the jurors in the Dedham trial had his house bombed, throwing him and his family from their beds. Less than a year after the executions, a bomb destroyed the front porch of the home of executioner Robert Elliott. As late as 1932, Judge Thayer's home was wrecked and his wife and housekeeper injured in a bomb blast. Afterward, Thayer lived permanently at his club in Boston, guarded 24 hours a day until his death.

In the fall of 1928, Upton Sinclair published his novel Boston, an indictment of the American judicial system that took the case, especially Vanzetti's life and writings, as its focus, mixing fictional characters with actual participants in the trials. Though his portrait of Vanzetti was entirely sympathetic, he disappointed advocates for the defense by failing to absolve Sacco and Vanzetti of the crimes, however much he argued that their trial had been unjust. Years later, he explained: "Some of the things I told displeased the fanatical believers; but having portrayed the aristocrats as they were, I had to do the same thing for the anarchists."

When the letters Sacco and Vanzetti wrote appeared in print in 1928, journalist Walter Lippmann commented: "If Sacco and Vanzetti were professional bandits, then historians and biographers who attempt to deduce character from personal documents might as well shut up shop. By every test that I know of for judging character, these are the letters of innocent men." On January 3, 1929, as Gov. Fuller left the inauguration of his successor, he found a copy of the Letters thrust at him by someone in the crowd. He knocked it to the ground "with an exclamation of contempt."

Intellectual and literary supporters of Sacco and Vanzetti continued to speak out. In 1936, on the day when Harvard celebrated its 300th anniversary, 28 Harvard alumni issued a statement attacking the University's retired President Lowell for his role on the Governor's Advisory Committee in 1927. They included Heywood Broun, Malcolm Cowley, Granville Hicks, and John Dos Passos.

Following the SJC's assertion that it could not order a new trial even if there was new evidence that "would justify a different verdict," a movement for "drastic reform" quickly took shape in Boston's legal community. In December 1927, four months after the executions, the Massachusetts Judicial Council cited the Sacco and Vanzetti case as evidence of "serious defects in our methods of administering justice." It proposed a series of changes designed to appeal to both sides of the political divide, including restrictions on the number and timing of appeals. Its principal proposal addressed the SJC's right to review. It argued that a judge would benefit from a full review of a trial and that no one man should bear the burden in a capital case. A review could defend a judge whose decisions were challenged and make it less likely that a governor would be drawn into a case. It asked for the SJC to have right to order a new trial "upon any ground if the interests of justice appear to inquire it." Governor Fuller endorsed the proposal in his January 1928 annual message.

It took another dozen years before the proposed language was adopted in 1939 and the SJC gained the authority to consider an entire case on the law and on the evidence or "for any other reason that justice may require."

Many historians, especially legal historians, have concluded the Sacco and Vanzetti prosecution, trial, and aftermath constituted a blatant disregard for political civil liberties, especially Thayer's decision to deny a retrial. Judge Webster Thayer, who heard the case, allegedly described the two as "anarchist bastards."

Both men had previously fled to Mexico, changing their names in order to evade draft registration required for citizenship application, a fact used against them by the prosecutor in their trial for murder. This implication of guilt by the commission of unrelated acts is one of the most persistent criticisms leveled against the trial. Sacco and Vanzetti's supporters would later argue that the men merely fled the country to avoid persecution and conscription, their critics, to escape detection and arrest for militant and seditious activities in the United States. But other anarchists who fled with them revealed the probable reason in a 1953 Book:

Several score Italian anarchists left the United States for Mexico. Some have suggested they did so because of cowardice. Nothing could be more false. The idea to go to Mexico arose in the minds of several comrades who were alarmed by the idea that, remaining in the United States, they would be forcibly restrained from leaving for Europe, where the revolution that had burst out in Russia that February promised to spread all over the continent.

Some critics felt that the authorities and jurors were influenced by strong anti-Italian prejudice and prejudice against immigrants widely held at the time, especially in New England. Fred Moore compared the chances of an Italian getting a fair trial in Boston to a black person getting one in the American South. Against charges of racism and racial prejudice, others pointed out that both men were known anarchist members of a militant organization, members of which had been conducting a violent campaign of bombing and attempted assassinations, acts condemned by the Italian-American community and Americans of all backgrounds. Though in general anarchist groups did not finance their militant activities through bank robberies, a fact noted by the investigators of the Bureau of Investigation, this was not true of the Galleanist group, as Mario Buda readily admitted to an interviewer: "Andavamo a prenderli dove c'erano" ("We used to go and get it [money] where it was") — meaning factories and banks. Others believe that the government was really prosecuting Sacco and Vanzetti for the robbery-murders as a convenient excuse to put a stop to their militant activities as Galleanists, whose bombing campaign at the time posed a lethal threat, both to the government and to many Americans. Faced with a secretive underground group whose members resisted interrogation and believed in their cause, Federal and local officials using conventional law enforcement tactics had been repeatedly stymied in their efforts to identify all members of the group or to collect enough evidence for a prosecution.

Most historians believe that Sacco and Vanzetti were involved at some level in the Galleanist bombing campaign, although their precise roles have not been determined. The Galleanists' bombmaker, Mario Buda, reportedly told a friend in 1955, "Sacco c'era" (Sacco was there). In 1941, anarchist leader Carlo Tresca, a member of the Sacco and Vanzetti Defense Committee, told Max Eastman, "Sacco was guilty but Vanzetti was innocent" Eastman published an article recounting his conversation with Tresca in National Review in 1961. Later, others would confirm being told the same information by Tresca. Others pointed to an ongoing feud between Tresca and the Galleanisti, claiming the famous anarchist was just trying to get even. Labor organizer Anthony Ramuglia, an anarchist in the 1920s, said in 1952 that a Boston anarchist group had asked him to be a false alibi witness for Sacco. After agreeing, he had remembered that he had been in jail on the day in question, so he could not testify.

In October 1961, ballistic tests were run with improved technology using Sacco's Colt automatic. The results confirmed that the bullet that killed Berardelli in 1920 was fired from Sacco's pistol. Subsequent investigations in 1983 also supported this finding.

In 1988, Charlie Whipple, a former Boston Globe editorial page editor, revealed a conversation that he had with Sergeant Edward J. Seibolt in 1937. According to Whipple, Seibolt said that the police ballistics experts had switched the murder weapon, but Seibolt indicated that he would deny this if Whipple ever printed it. At the time, Whipple was unfamiliar with the specific facts of the case, and it is not known if Seibolt was actually recalling Albert Hamilton's testimony and behavior on the stand when Hamilton apparently switched Sacco's gun barrel with that of another Colt automatic.

Sacco's .32 Colt pistol is also claimed to have passed in and out of police custody, and to have been dismantled several times, both in 1924 prior to the gun barrel switch, and again between 1927 and 1961. The central problem with these charges is that the match to Sacco's gun was based not only on the 0.32 Colt pistol but also on the same-caliber bullet that killed Berardelli as well as spent casings found at the scene. In addition to tampering with the pistol, the gun switcher/dismantler would have had also to access police evidence lockers and exchange the bullet from Berardelli's body and all spent casings retrieved by police, or else locate the actual murder weapon, then switch barrel, firing pin, ejector, and extractor, all before Goddard's examination in 1927 when the first match was made to Sacco's gun. However, doubters of Sacco's guilt have repeatedly pointed to a single anomaly — that several witnesses to the crime insisted the gunman, alleged to be Sacco, fired four bullets into Berardelli. "He shot at Berardelli probably four or five times," one witness said. "He stood guard over him." If this was true, many ask, how could only one of the fatal bullets be linked to Sacco's gun? In 1927, the defense raised the suggestion that the fatal bullet had been planted, calling attention to the awkward scratches on the base of the bullet that differed from those on other bullets. The Lowell Commission dismissed this claim as desperate but in 1985, historians William Kaiser and David Young made a compelling case for a switch in their book Postmortem: New Evidence in the Case of Sacco and Vanzetti.

In 1973 a former mobster published a confession by Frank "Butsy" Morelli, Joe's brother. "We whacked them out, we killed those guys in the robbery," Butsy Morelli told Vincent Teresa. "These two greaseballs Sacco and Vanzetti took it on the chin."

Before his death in June 1982, Giovanni Gambera, a member of the four-person team of anarchist leaders that met shortly after the arrest of Sacco and Vanzetti to plan their defense, told his son that "everyone [in the anarchist inner circle] knew that Sacco was guilty and that Vanzetti was innocent as far as the actual participation in killing." Russell had originally written about the case, arguing that Sacco and Vanzetti were innocent, but further research led him to write a 1975 book, asserting that Sacco was, in fact, guilty. Russell used the Gambera revelation as the basis of a new book in 1986, in which he claims that the case is "solved," and presents his view that Sacco was one of the shooters, while Vanzetti was an accessory after the fact. While Russell's 1975 book was praised, even by those who disagreed with his conclusion, for being balanced and well-reasoned, his 1986 book was much more negatively received.

Months before he died, the distinguished jurist Charles E. Wyzanski, Jr., who had presided for 45 years on the U.S. District Court in Massachusetts, wrote to Russell stating "I myself am persuaded by your writings that Sacco was guilty." The judge's assessment was significant, because he was one of Felix Frankfurter's "Hot Dogs," and Justice Frankfurter had advocated his appointment to the federal bench.

In 1977, as the 50th anniversary of the executions approached, Massachusetts Governor Michael Dukakis asked the Office of the Governor's Legal Counsel to report on "whether there are substantial grounds for believing – at least in the light of the legal standards of today – that Sacco and Vanzetti were unfairly convicted and executed" and to recommend appropriate action. The resulting "Report to the Governor in the Matter of Sacco and Vanzetti" detailed grounds for doubting that the trial was conducted fairly in the first instance and argued as well that such doubts were only reinforced by "later-discovered or later-disclosed evidence." The Report questioned prejudicial cross-examination that the trial judge allowed, the judge's hostility, the fragmentary nature of the evidence, and eyewitness testimony that came to light after the trial. It found the judge's charge to the jury troubling for the way it emphasized the defendants behavior at the time of their arrest and highlighted certain physical evidence that was later called into question. The Report also dismissed the argument that the trial had been subject to judicial review, noting that "the system for reviewing murder cases at the time... failed to provide the safeguards now present." Based on recommendations of the Office of Legal Counsel, Dukakis declared August 23, 1977, the 50th anniversary of their execution, Nicola Sacco and Bartomomeo Vanzetti Memorial Day. His proclamation, issued in English and Italian, stated that Sacco and Vanzetti had been unfairly tried and convicted and that "any disgrace should be forever removed from their names." He did not pardon them, because that would imply they were guilty. Neither did he assert their innocence. A resolution to censure the Governor failed in the Massachusetts Senate by a vote of 23 to 12. Dukakis later expressed regret only for not reaching out to the families of the victims of the crime.

A memorial committee attempted to present a plaster cast executed in the 1937 by Gutzon Borglum, the sculptor of Mount Rushmore, to Massachusetts governors and Boston mayors in 1937, 1947, and 1957 without success. On August 23, 1997, on the 70th anniversary of the Sacco and Vanzetti executions, Boston's first Italian-American Mayor Thomas Menino and the Italian-American Acting Governor of Massachusetts Paul Cellucci unveiled the work at the Boston Public Library, where it remains on display. "The city's acceptance of this piece of artwork is not intended to reopen debate about the guilt or innocence of Sacco and Vanzetti," Menino said. "It is intended to remind us of the dangers of miscarried justice, and the right we all have to a fair trial." The event occasioned a renewed debate about the fairness of the trial in the editorial pages of the Boston Herald. There is also a mosaic mural of the trial of Sacco and Vanzetti on the main campus of Syracuse University.

The "Sacco and Vanzetti Century" was an American anarchist military unit in the Durruti Column that fought in the Spanish Civil War.

There are many objects in the former USSR named after "Sacco and Vanzetti", for example a beer production facility in Moscow, a kolkhoz in Donetsk region, Ukraine, and an apartment complex in Yekaterinburg. There are also numerous towns in Italy that have streets named after Sacco and Vanzetti, including Via Sacco-Vanzetti in Torremaggiore, Sacco's home town, and Villafalletto, Vanzetti's.