For every action, Newton’s third law of motion states, there is an equal and opposite reaction. And for every bellwether moment in American history, it seems that there are revisions, reappraisals, periodically renewed outrages, and accusations of conspiracy equal and opposite to the facts. The arrest, trial, and execution of Nicola Sacco and Bartolomeo Vanzetti in Massachusetts in 1927 is just such an event.

Sacco was a cobbler and Vanzetti was a fishmonger. Both men relocated to Massachusetts from Italy in search of a new start and new freedom. Unfortunately, their arrival occurred at a time when Italian immigrants bore the brunt of native born Anglo-American prejudice. Much more unfortunately, both were avowed anarchists. On April 15, 1920, a pair of armed men robbed a Braintree, Mass., factory payroll of nearly $16,000 and killed the factory’s paymaster in the process.

A usual-suspects roundup in 1920s red-scare America often included known communists, socialists, and other political dissenters. Sacco and Vanzetti were followers of the anarchist Luigi Galleani, who was deported for advocating violence and whose associates were suspects in a pair of terrorist bombings. On the strength of that association, as much as on physical evidence, the two were arrested and indicted on charges of robbery and murder.

The police investigation of the robbery was riddled with inconsistencies, and from this distance offers conflicting historical evidence as to the men’s actual guilt. Nevertheless, Sacco and Vanzetti were convicted, sentenced, and executed in the electric chair. “This man,” the presiding judge, Webster Thayer, told the trial jury on the subject of Vanzetti’s guilt, “although he may not have committed the crime attributed to him, he is nevertheless culpable because he is the enemy of our existing institutions.”

What no amount of revision and reappraisal alters is that Sacco and Vanzetti received very little of the protections that the Constitution promised them. Their ordeal is a chapter in the American story that encompasses the prejudicial revocation of guaranteed civil liberties, a trial by media, and the fate of politically dissenting immigrant have-nots run afoul of an all-powerful legal system run by native haves who answer only to one another. In 2007, the tragic story of the two Italian anarchists seems tailor-made to X-ray contemporary political, social, and cultural trends and woes, from “Judge Judy”-style tabloid justice to the plight of Guantanamo Bay detainees.

Peter Miller’s new documentary, “Sacco And Vanzetti,” does a thorough job of identifying intersections between yesterday’s and today’s headlines as it parses out the facts in the case of the two men. Mr. Miller’s documentary producing credits are impressive. His previous collaborators include such established nonfiction film heavyweights as George Stoney, Barbara Kopple, and Ken Burns. Stylistically, “Sacco and Vanzetti,” Mr. Miller’s sophomore outing as a director, sticks closely to the unofficial historical documentary style sheet that Mr. Burns has popularized.

Sacco and Vanzetti were prodigious correspondents and their letters are voiced in first-person by actors, just as they would be in one of Mr. Burns’s films. The camera drifts across and zooms deep into period photographs. Contemporary authorities on the subject hold forth with intimate conviction in talking head close-ups. Period newsreel footage is scored with popular music and protest songs of the day.

But beneath the smooth surface of “Sacco And Vanzetti” beats the heart of a rigorously designed and deeply affecting piece of agitprop. “Time rather than softening my loss, made it more cruel,” Nicola Sacco, voiced with unusual ease by Tony Shaloub (John Turturro reads Vanzetti), says on the subject of his mother’s death. In Mr. Miller’s film the same is true of Sacco and Vanzetti’s execution. Any remaining questions about the two men’s guilt appear to have receded into the dim past, while the outrage at their execution feels like it’s still building steam.

The default star of Mr. Burns’s career-making series, “The Civil War,” was the historian Shelby Foote. Whenever that film threatened to devolve into a historical connect the dots, Mr. Foote would pop up with an impassioned and intelligent anecdote that contextually bridged the decades. The equivalent voice of reason and compassion in “Sacco And Vanzetti” belongs to Howard Zinn. The author of “A People’s History of the United States” speaks with charisma and candor on the case, both in interviews and from a college lectern.

“Sacco and Vanzetti” supplants vintage film footage with clips of Henry Fonda pleading in a mock trial of the two men in the 1942 film version of James Thurber’s “The Male Animal.” Is there any more potent mainstream movie crusading persona than Fonda’s? Mr. Miller’s film also uses footage from Giuliano Montaldo’s 1971 Italian movie drama, “Sacco e Vanzetti.” But what initially appears to be a lazy attempt to sweeten the bitter facts of history with a sugar coating of Technicolor razzamatazz ends up providing yet another persuasive opinion.

Mr. Montaldo, that film’s now 77-year-old writer and director, appears in recent interview segments. He makes it clear that his film, like Mr. Miller’s, was a labor of love and that the story of Nicola Sacco and Bartolomeo Vanzetti will continue to catalyze artistic reaction for decades to come.