Rather like the arc of the moral universe, “Argentina, 1985” is long, but bends toward justice. Effectively dramatizing the country’s landmark Trial of the Juntas, history’s first instance of a civilian justice system convicting a military dictatorship, Santiago Mitre’s broad, sprawling, heart-on-sleeve courtroom saga may draw from the same nightmarish period of history that has informed much of Argentine cinema’s most essential, haunting works — from 1985’s Oscar-winning “The Official Story” to last year’s “Azor” — but eschews any subtle arthouse stylings for a storytelling sensibility as robustly populist as anything by Sorkin or Spielberg.

Small wonder, then, that Amazon Studios has boarded a film clearly aiming to be both a domestic smash and an international crossover hit — buoyed by the reliable star power of Ricardo Darín, his signature suaveness tempered by a walrus mustache and boxy ‘80s frames as Julio Strassera, the dogged prosecutor who took on this charged, against-the-odds case. Though a warmly received premiere in competition at Venice will set it on the right path, “Argentina, 1985” is, appropriately enough, a people’s film about people’s justice, balancing tear-jerking historical catharsis with touches of droll domestic comedy, and set to draw crowds on enthusiastic word of mouth.

For Mitre, himself but a kindergartener when the true-life events of “Argentina, 1985” unfolded, his latest represents an advance on his Cannes-selected 2017 political thriller “The Summit,” retaining that film’s mainstream genre smarts — and, of course, the redoubtable services of Darín — but kicking up the style a notch. Javier Juliá’s velvety, deep-hued lensing, Micaela Saiegh’s worn-in period production design and Andrés Pepe Estrada’s jittery editing grant cinematic sweep and scope to a story that could otherwise favor a televisual format: This is, after all, a trial in which 833 witnesses testified over the course of five months, so even at a chunky 140 minutes, Mitre and Mariano Llinás’s screenplay can’t help but feel cannily condensed.  

The film begins with a somewhat cluttered procession of title cards outlining the historical context for any international viewers unfamiliar with the history of Argentina’s Dirty War, which saw a right-wing military junta seize power from 1976 to 1983, killing and kidnapping some 30,000 civilians perceived as opponents. In a restored democracy still finding its feet, the film shows the defeated military to still wield undue influence in high places, as well as on certain still-deceived factions of the public: When nine of the dictatorship’s commanders are charged with war crimes, they insist on being tried in a military court that goes predictably easy on them.

When the trial is turned over to civilian jurisdiction, however, stout-hearted public prosecutor Strassera senses a once-in-a-generation opportunity for redress — though even in this reborn Argentina the system is stacked against him, with new president Alfonsin seemingly reluctant to support a conviction. Finding the country’s legal old guard not fit for purpose — in one wittily written scene, he swiftly divides a list of potential collaborators into the dead, the fascist and the super-fascist — he instead takes on young, politically impassioned co-counsel Luis Moreno Ocampo (a winning Peter Lanzari) and a team of wet-behind-the-ears law graduates to gather research, evidence and witnesses.

The courtroom scenes alternate between fiery rhetorical bluster and chilling testimony ripped more or less directly from the record, with flashes of archival footage seemingly spliced between the drama. In the film’s most heart-stopping scene, a young woman reflects on her experience of being forced to give birth bound and blindfolded while being held captive by the junta. That “Argentina, 1985” managed to toggle between such emotionally raw material and more amped-up, tension-driven subplots — as Strassera and his family weather death threats and cars explode in public squares — without seeming callous or dramatically opportunistic is a credit to Mitre, whose grasp on his story is high-key and emotionally immediate, but never glib. 

It’s also a testament to the appealingly grounded star quality of Darín, who makes Strassera a noble, cheer-worthy crusader in a classically heroic mode, yet with a warm, scruffy peculiarity that keeps any potential dourness at bay. Well-drawn scenes with his family at home show he’s as anxious and uncertain as any member of the public about the system he’s taking on, though when he’s called upon to square his shoulders and deliver a final indictment, he does so with a doughty conviction that makes for one of the most riveting, hair-raising scenes of speechifying in recent cinema. It’s lengthy, like the film, and worth the earful: “Argentina, 1985” may be full of sharp Hollywood savvy, but it knows when not to sell history short.