On the afternoon of Friday, April 15, 1920, in South Braintree, Massachusetts, two men approached a couple of security guards delivering the payroll money for the Slater and Morrill Shoe Factory, and without warning, they opened fire.  One of the men shot both guards, and the other pumped several more bullets into them.  They then took the payroll boxes containing nearly $16,000 and sped off in a black Buick with three other men.  Eyewitnesses described them as "Italian-looking" and one had a handlebar mustache.

Mike Boda, police mugshot

Investigators recovered six ejected shell casings from the sidewalk around the dead men and traced them back to three manufacturers: Remington, Winchester and Peters.  They also found the getaway car, abandoned, and they soon linked it with an earlier robbery.  Police surmised that the mastermind was an Italian thug named Mike Boda, but when they located his hideout, he had already fled to Italy.

Nicola Sacco’s Colt & Bartolomeo Vanzetti’s H&R

However, two of his associates were arrested, some sources say at Boda's hideout, some say on a streetcar.  They were ordinary Italian laborers who fit the general descriptions: Nicola Sacco, 29, and Bartolomeo Vanzetti, 32,.  While they denied owning guns, they had illegal pistols on their person and Sacco's was the same caliber—a .32 Colt automatic—as the murder weapon.  Sacco also sported a handlebar mustache and had two dozen bullets on him made by the three manufacturers matched to the shells.  Both men were also members of a radical anarchist group that supported violence to resolve injustice.  They were promptly arrested.

Nicola Sacco

Sacco was tried for robbery in the earlier case and found guilty.  He was later tried with his partner, Vanzetti, for the murder of Alessandro Berardelli, one of the shoe company security guards.

The trial began on May 31, 1921, and public opinion was clearly against them.  Regardless of their guilt or innocence in the murders, they were perceived as dangerous men.  Yet there were many foreigners, feeling the burn of xenophobia, who sided with them and the Sacco-Vanzetti Defense Committee called the whole ordeal a witch-hunt, with these men serving as scapegoats for America's fear of the political beliefs of other countries.

Bartolomeo Vanzetti

Four bullets had been removed from the murdered payroll guards.  Experts were brought in to testify as to whether Sacco's .32 pistol was indeed the murder weapon, and on the prosecution side, opinions were mixed.  The experts for the defense were more confident in their opinion, although no one had based what they offered on scientific techniques. All were self-taught.

Nevertheless, the verdict that both men were guilty was likely based on one significant fact that had little to do with what the experts had said: the bullet that had killed Berardelli was so outdated that the only bullets similar to it that anyone could locate to make comparisons were those in Sacco's pockets.  The jury had even used a magnifying glass to examine the bullets for themselves, and had finally bought the prosecution's case.  The defendants were sentenced to death and a date was set.

David Owen's Hidden Evidence

Around the world, these two men were portrayed as innocent victims to American fears and to a capitalist system.  Right away another expert entered the fray and declared the others frauds.  According to David Owen in Hidden Evidence, that expert’s opinion was sufficient to get the verdict overturned and a hearing for a new trial.

To bolster its side, the defense had hired Albert H. Hamilton to definitively state that the gun in the possession of the two men was not the murder weapon.  This same expert had testified six years earlier in another case—that of Charles Stielow, a German immigrant convicted in the double homicide of his employer, Charles Phelps, and Phelps' housekeeper, Margaret Wolcott.  Both had been shot to death with a .22 caliber revolver.  According to the account on the History Channel's Forensic Firsts, Stielow was quickly arrested and found to own such a weapon.  He'd even tried to hide it.  Since he wanted to go home to his wife, he confessed, believing he would be released.  He would not sign a statement, however, and once in jail, he recanted the confession.

Hamilton, whom Evans says passed himself off falsely as a doctor, was a hired gun.  He would say whatever he was paid to say, and among his many professed specialties was firearms.  He claimed to be able to match an abnormal scratch in the barrel of Stielow's weapon to marks on the bullets.  He even took photographs to further impress the jury, although he had to admit one could not see the scratches on them.  However, he had never test-fired the gun.  When asked to point out the scratch on the gun barrel, he said it could not be done because the bullet's momentum had expanded the bullet in such a way as to fill in the scratch, rendering it invisible.  As nonsensical as it sounds in retrospect, the jury believed it and Stielow was convicted and sentenced to die.  Only at the last minute was he spared when two drifters were caught who confessed.  Hamilton's glib pseudo-science had nearly sent an innocent man to his death.  It had also cost the county so much money that it declined to prosecute the real killers.

Added to that, an examination of Stielow's gun found that it had such a rust buildup that it could not have been fired in several years. 

In 1917, the bullets were brought to a lab in New York.  Officer Charles Waite first fired test bullets identical to those found in the bodies from Stielow's gun into water. Then optics expert Max Poser examined the bullets under a high-powered microscope and could not see any of the alleged scratches that Hamilton had "observed."  He then found that the murder bullets had been fired from a weapon with an abnormal land-and-groove pattern—a manufacturer's defect---whereas Stielow's gun was normal, so it could not have been the murder weapon.  Stielow could have been excluded very early in the case.

Although humiliated, Hamilton inexplicably continued to make his mark in the legal system.  Hired by Sacco and Vanzetti's lawyers, he wasted no time in making authoritative pronouncements based on no real expertise.

So the prosecution's expert, Charles Van Amburgh, re-examined the evidence in 1923, when bullet comparison technology had improved somewhat.  He enlarged the photos of the fatal wounds and the photos of the bullets fired from Sacco's revolver.  He insisted they were identical, and he prepared for a retrial of the two men.

With his usual cunning, Hamilton tried to pull off a sleight-of-hand that would prove his point.  He brought in Sacco's .32 and two new Colt revolvers.  There in court, he disassembled them all and then tried to exchange one of the new barrels with the one from Sacco's gun.  Judge Thayer saw what he was doing and demanded he return the original barrel for Sacco's gun.  Thayer then denied the motion for another trial.  Hamilton had blown it, both for the defense and for himself.

Yet a committee was appointed to review the case and they contacted Calvin Goddard in 1927, who had worked with Charles Waite at the Bureau of Forensic Ballistics in New York.  He used Philip Gravelle's newly invented comparison microscope and helixometer, a hollow lighted magnifier probe used to inspect gun barrels, to make a rigorous examination.  In the presence of one of the defense experts, he fired a bullet from Sacco's gun into a wad of cotton and then put the ejected casing on the comparison microscope next to casings found at the scene.  Then he looked at them carefully.  The first two casings were no match, but the third one was.  Even the defense expert agreed that these two bullets had been fired from the same gun.  The second original defense expert also concurred, and that clinched the case.  That same year, the two men went to the electric chair.  Vanzetti still claimed he was innocent, while Sacco said, "Long live anarchy!"

Subsequent investigations with better technology in 1961 and 1983 both supported Goddard's findings.  Even so, in 1977, the governor of Massachusetts issued a proclamation for their innocence, and the case still remains controversial.