ROME — An epic trial of Italy’s most powerful mafia families has ended with life sentences for four godfathers, decapitating a clan worth an estimated $40 billion.

The Casalesi clan, which took its name from the town of Casal di Principe near Naples, has been described as the successor to the Corleone family, which ruled Sicily in the 1980s.

The clan is thought to have carried out more than 1,000 murders in the past 30 years to establish an iron grip on the area between Naples and Salerno.

However, Francesco Schiavone, the head of the clan, will now spend the rest of his life in prison after being convicted yesterday.

The 10-year legal action, named the Spartacus Trial in recognition of the need to fight a revolution in the Casalesi’s territory, charged 36 members of the syndicate with a string of murders and other crimes. All were found guilty and 16 of them will never be released.

“This is the most important trial in the last 20 years,” said Roberto Saviano, a best-selling author whose book about the clan, “Gomorra,” has recently been turned into a prize-winning film.

Mr. Saviano, who is under police protection, said that more than 500 witnesses had testified and that the heaviest penalties ever for organized crime had been meted out, a total of 700 years of imprisonment.

Francesco Bidognetti, known as Cicciott’ ‘e Mezzanotte (Midnight Fatty), was given life imprisonment. Michele Zagaria and Antonio Iovine, two other godfathers, got the same sentence but are currently on the run. Over the course of the initial trial and the appeal, five people involved in the case were murdered, including an interpreter. A judge and two journalists were threatened with death.

The court was housed in a top security prison in the Poggioreale district of Naples. Only two of the defendants were in the heavily-guarded courtroom to hear the verdict, while others followed it via videolink from their prison cells.

The presiding judge, Raffaello Magi, said: “Unlike the Neapolitan gangsters who live off cocaine dealing or extortion, the Casalesi exploit every area of economic potential. They do the dumping of the toxic refuse, they hold the monopoly on the cement market, they control the distribution of essential products. They control elections and they offer protection and market opportunities to businesses.”

Any business wanting to open in the area had to pay the clan for permission and then buy cement from them to build their buildings.

The clan is believed to have built parts of the motorway between Rome and Naples and even the prison at Santa Maria Capua Vetere in which many of its members are now held.