The 1986 Maxi Trial, in which 475 members of the Sicilian Mafia, known as Cosa Nostra, were indicted for their crimes, is an event absolutely ripe for cinematic adaptation. Held in a bunker of a courthouse inside the Palermo prison, the accused Mafiosi watched the proceedings from behind bars, in cells where they smoked, played cards and heckled the judges.

They reserved their worst ire for the witnesses, though, their former friends, mob bosses-turned-informants. It’s here that director/co-writer Marco Bellocchio and his co-writers Valia Santella, Ludovica Rampoldi, Francesco Piccolo and Francesco La Licata find inspiration for the sprawling Italian gangster epic “The Traitor.” It follows the life, times and crimes of famous informant Tommaso Buscetta, played marvelously by Pierfrancesco Favino, who tears into this meaty role of a lifetime.

First and foremost this is Buscetta’s story, a dive into the reasons why a Cosa Nostra lifer, a self-declared man of honor and loyalty, would find informing the most honorable thing to do. Favino’s performance is the center of gravity for the film, which encompasses nearly a century’s worth of Sicilian Mafia lore. Without such a compelling lead actor to hold it all together, the focus would be lost.

The film opens in the late ’70s, on his waning days as a mobster at a raucous celebration with his nearest and dearest. The photo taken that night will later come back to haunt them as proof that Buscetta was once considered family, a relationship that colors the sickening murders carried out later against his family members. Extradited from Brazil on charges of drug trafficking, Buscetta decides to collaborate with Judge Giovanni Falcone in light of the murder of his adult sons. He claims his own honor and loyalty in the process because he believes the heroin trafficking and child-murdering Cosa Nostra of this era, shepherded by Salvatore Riina, isn’t the Cosa Nostra that Buscetta joined as a teenager in Palermo in the 1940s.

Favino is magnetic, but there are so many rich characters and story lines to follow in the wild true-crime tale, and Bellochio wants to chase them all. There are a few strange stylistic choices, like an inexplicable on-screen ticker counting the murders and an abundance of titles signifying dates and locations. Bizarre and abrupt scene transitions and surreal dream sequences create a jarring tone and undercut its suspense.

The most riveting moments are the testimony and trial scenes, whether Buscetta is justifying why he’s divulging the inner workings of Cosa Nostra to Falcone or appearing before the court and his former compatriots. The morbid pageantry of the trial, with Buscetta ensconced in a protective chamber, facing away from the menacing Mafia men, is incredibly compelling, while he simultaneously makes the case against them and for himself.

The scenes outside of the courtroom are at times disjointed, rife with random memories, dreams and flashbacks, not as tightly controlled as the legal drama at the heart of the matter. But it’s necessary for Bellocchio to include Buscetta’s history and connections and his subsequent life in witness protection to illustrate just how explosive his collaboration with authorities truly was, and to show Buscetta in context to his family (both by blood and by oath). Because fundamentally, “The Traitor” is about the lengths individuals will go to to protect or destroy a family, in this outlandish Mafia tale you wouldn’t believe if it weren’t true.