Marco Bellocchio’s The Traitor is a big, handsomely shot, true-crime gangster movie, ranging over 30 years from the early 1970s to the late 90s, scripted by Bellocchio with screenwriters Valia Santella, Ludovica Rampoldi and Francesco Piccolo. The film has the authoritative air of official history: sometimes brash, sometimes stolid, sometimes with flashes of inspiration and sometimes with long stretches of courtroom dialogue. It is in these sections where Bellocchio is perhaps self-consciously concerned, as a major Italian film-maker, to be seen delivering a definitive cinematic account of an important period of modern Italian life. Well, it was certainly a sound instinct to show the courtroom scenes at some length, because however bizarre and chaotic it could be, the court of law is the moral centre of these events.

His subject is Italy’s sensational anti-mafia Maxi trial of 1986, in which hundreds of Sicilian mobsters were convicted, on the testimony of a tiny number of high-up pentiti, or informers, of which the most important was Tommaso Buscetta, a bulkily intimidating, charismatic presence portrayed here by Italian character actor Pierfrancesco Favino. He was the important Cosa Nostra guy who astonished everyone by committing the ultimate sin: treason. He snitched to the cops. It was something that made him lower than the low: hated not merely by the police and the media but his own people, too. The film tells Buscetta’s story, flashing backwards and forwards between his life as a young Palermo guy starting out in crime, to the elderly, morose type in a witness-protection scheme in the United States, paranoically buying semi-automatics at the local supermarket because they were on a special discount.

Bellocchio begins his story in medias res, at a huge mafia clan meeting in 1980 theoretically intended as a diplomatic summit, to carve up Italy’s heroin market between them as peacefully as possible, but really as an exercise in tacit threat. He brings his camera into some fierce, almost reptilian faces, lit by outdoor torches – and maybe he has been influenced by the young(er) master, Paolo Sorrentino. Tommaso himself seems even-tempered enough, though furious at his young son’s addiction to heroin – the one time in the film the actual effects of his merchandise are shown.

Soon, Tommaso has taken his extended family over to Rio de Janeiro, supervising the Latin American connection in what amounts to commercial exile, but his absence from Italy is a serious mistake. Rival wiseguy Totò Riina (Calì Nicola) launches a pre-emptive strike against Tommaso’s family members and allies, including Totuccio Contorno (Luigi Lo Cascio) – we get the traditional montage of guys with their faces pressed against the steering wheel behind a cobwebbed windshield. This calamitous war focuses the minds of law enforcement in Italy, Brazil and the US, and in response to threats to his wife Cristina (Maria Fernanda Cândido), Tommaso realises he has no choice to but to turn state’s evidence. Now he is a supergrass, brought back in first class to Italy to blow the lid.

There really are some show-stopping scenes: perhaps especially when Tommaso and Cristina are taken out over the ocean in separate helicopters and Tommaso is made to watch as his terrified wife is dangled out, about to be dropped. This horrific threat is what convinced him to snitch, we are given to understand. Who can blame him? Perhaps those who think that this episode is a self-serving fantasy of Tommaso’s to justify ratting out his fellow bad guys. At any rate, Bellocchio takes the anecdote at face value, and it’s a sensational image. The attempted shooting of Contorno is white-knuckle stuff, and there is a very good performance from that other Italian acting veteran Luigi Lo Cascio — whom I first saw in Giuseppe Piccioni’s excellent 2001 movie Light of My Eyes.

Then there is the notorious murder of the trial judge, Giovanni Falcone (Fausto Russo Alesi), when his car was bombed on the autostrada, and Bellocchio’s camera occupies the interior of his car as it flips up through the air. It is an extraordinary scene, followed by the mobsters’ ugly gloating and celebrating. Bellocchio shows how at this moment the mafia have revealed themselves to be not glamorous warriors, but grotesque and spiteful bullies. The director also makes a very interesting suggestion towards the end: people like Tommaso want to snitch, because they have a secret craving for their importance to be recognised, and to put the seal on their careers: despite the hate, they want things put on the record.

The Traitor is acted and directed throughout with confidence and force, but somehow it lacks the lightning-flash of inspiration of something like Scorsese’s Goodfellas – a similar story of mobsters snitching – because it never quite relaxes into the gangsters’ ordinary lives. There isn’t quite enough human interest or incidental detail of the sort that made Goodfellas so unmissable. But The Traitor is big, bold, confident film-making.