Extraordinarily, it is also an issue that has roared back to life in the past week. Nearly a quarter of a century after the fact, and following seven trials and appeal hearings, three men have been sentenced for ordering and carrying out the killing of a man who was once the most hated policeman in Italy.
Italy's High Court ruled last Wednesday that Adriano Sofri, Giorgio Pietrostefani and Ovidio Bompressi - all of them former members of a prominent left- wing agitprop group called Lotta Continua - were to be denied any possibility of further appeal and sent to prison for 22 years apiece. The problem is that almost nobody in Italy believes them to be guilty, and even fewer believe they should be made to pay for the follies of an era that by now is almost a generation in the past.
It has been an astonishing spectacle, as political parties on all sides have tried to use the case for their own campaigning purposes and a beleaguered judiciary has lamely sought to defend a case with more holes than an Emmental cheese.
The original story will be familiar to anyone who saw Dario Fo's hit play Accidental Death of an Anarchist. In the winter of 1969 some shady right-wing organisations responded to a rash of mass industrial unrest with a series of bombings, including an attack on a bank in Piazza Fontana, Milan, that killed 16 people and injured nearly 100.
We now know that the bombings were part of a deliberate "strategy of tension", orchestrated by some sections of the political establishment in collusion with the secret services to counter the rise of the New Left in 1968 and scare voters away from the Communist Party. At the time, though, it was far from clear who was responsible for the attacks, and a massive disinformation campaign was launched to pin the blame on left- wing anarchists and groups such as Lotta Continua. One anarchist, Pino Pinelli, was detained without due legal process for three days at the central police station in Milan, at the end of which he fell to his death from the window of Commissioner Calabresi's fourth-floor office. At first it was asserted he had committed suicide, then that he accidentally fell while smoking. Of course nobody ever believed such preposterous assertions.
Lotta Continua (the name means Continuous Struggle) launched a vicious counter-campaign accusing Calabresi and his colleagues of torturing and murdering Pinelli before throwing him out of the window. Unfortunately they had not a shred of proof, and before long the case landed in the courts where the judiciary dutifully fudged it and - years later, when the fuss had died down - shelved it altogether.
When Calabresi was shot outside his home in broad daylight, suspicion immediately fell on Lotta Continua but no case could ever be made against any of the organisation's members who were arrested sporadically over the next few years. By the turn of the 1980s the crime had turned into yet another unsolved Italian mystery, and the authorities gave up hope of ever bringing the commissioner's assailants to book.
But then, out of the blue, something very odd happened. In the summer of 1988, a petty crook and one-time Lotta Continua member, Leonardo Marino, turned himself in to the police saying he had taken part in Calabresi's murder. The hitman had been Ovidio Bompressi, he claimed, and the men who had approached him to take part were Sofri and Pietrostefani - leader and deputy leader of the now long-defunct Lotta Continua.
Marino's confession struck like a bombshell, not least because Sofri and Pietrostefani had become highly respected figures in their respective chosen fields of journalism and social work. But as the case unfolded, it also started to look highly suspect, as Marino's testimony betrayed more and more inconsistencies and became bogged down in ever more tortuous contradictions.
He claimed to have driven the getaway car, but slipped up on details such as the colour of the vehicle and the route he took away from the scene of the crime. Two eye-witnesses said the driver had been a woman, and others gave an account of how the murderer got in and out of the car that jarred completely with Marino's version.
Perhaps most seriously, Marino failed to mention - until his own parish priest inadvertently revealed it in court - that he had spent three weeks in unrecorded talks with the police before beginning his formal deposition. Friends of Sofri and Pietrostefani have suspected ever since that a plot was hatched with the police to take belated revenge on the Lotta Continua leadership, a theory that is widely believed but which, like so much else in this murky affair, has no evidence to support it.
Much of Italy has watched aghast as successive court hearings have rubber- stamped Marino's version of events and dismissed the credibility of other evidence in surreal fashion (one witness who said he saw a woman driving the getaway car was disregarded on the grounds that he was colour-blind).
The final High Court verdict has sparked a wave of national revulsion including sentiments of scarcely concealed contempt from government ministers. Only the far-right National Alliance came out in praise of the ruling.
The left sees the affair as a continuation of an ideological struggle that should by rights have subsided along with the end of the Cold War, while the followers of Silvio Berlusconi and his centre-right party Forza Italia have used the case as another stick with which to beat the Italian judiciary. Marino's confession, they argue, is exactly the sort of unreliable evidence used to nail politicians and businessmen during the anti-corruption wave of the early 1990s and has parallels, they say, in the various criminal cases at present being brought against Mr Berlusconi himself.
As for the defendants, Sofri and Bompressi were escorted to jail this weekend and Pietrostefani, who lives in Paris, announced he would be returning to Italy shortly to share their fate. Their only hope now is a presidential pardon - rare in Italy, but something that in the present climate of indignation they may yet be granted.