In Padua, on 20 January 1976, a young girl called Margherita Magello was repeatedly stabbed and left for dead. She was discovered by Massimo Carlotto, a 19-year-old student radical and member of Lotta Continua, who tried to save her, and, in doing so, got covered in her blood. She died, he was arrested and, a pawn in the struggle between Lotta Continua and the police, was tried for her murder. Just before sentence was pronounced, his lawyer advised him to run. He escaped to Paris and ended up in Mexico, where, in 1985, he was betrayed by a Mexican lawyer and extradited to Italy. Retried, he was found guilty and imprisoned until, in 1993, he was pardoned by the president.

arlotto is now almost 50, a good-looking, beefy man, normally photographed with a cigar poking out from greying stubble. Last year a film about his life called Il Fuggiasco ('The Fugitive') came out in Italy. Since his release, Carlotto has reinvented himself as a writer of hugely popular thrillers. More than merely hard-boiled, his novels are sexy, seedy, cynical and nihilistic, but with moments of idealism. Thanks in part to Carlotto, noir has become the boom genre of Italian publishing. Einaudi have introduced two new imprints, Stile libero and Stile libero Noir. The Sicilian publisher Sellerio is permanently at the top of the bestseller lists thanks to the octogenarian Andrea Camilleri, whose books have also been stylishly adapted for television. Carlo Lucarelli - co-editor of Stile libero Noir and another bestselling writer of thrillers - fronts a TV programme about real murder cases.

The Italian public seem permanently hungry for gialli. In bookshops you find shelf on shelf of Follett and Forsyth translations, as well as Italian thrillers. And when it comes to real-life gialli, practically every news programme announces 'a gripping new thriller unravelling' somewhere. Sub judice is ignored as bloodstains, bullet holes and murder weapons are shown, and reporters chase mourning mothers down the street, microphone in hand. As Hitchcock once said, 'television has brought murder back into the home - where it belongs.'

The greatest asset of the Italian thriller is that the reader doesn't need to suspend disbelief. So many astonishing and intricate crimes seem to take place in the country that the fictional ones appear perfectly probable. In some thrillers fictional mysteries are blended in with real ones. Carlotto, in his novels, hovers between reality and invention. In the postscript to The Colombian Mule he describes the man on whom one of the characters is based and outlines the techniques he and his fellow prisoners used to protect themselves from sexual predators ('two of us would wash while the third stood guard, a bathrobe rolled round his left arm and the handle of a frying pan, filed to razor sharpness, clasped in his right hand'). In an author's note at the end of The Shape of Water, Camilleri says that his book is fiction, even though 'in recent years reality has seemed bent on surpassing the imagination, if not entirely abolishing it.'

The emphasis on realism means that many Italian thrillers avoid neat resolutions. Miss Marple moments, when the entire cast is assembled and the detective delivers a tidy summary, are rare. In Italian whodunnits one may discover who did it, but - a reflection of Italian reality - the criminal is rarely collared; the writer gives you the satisfaction of solving the crime, but withholds the pleasure of letting you see justice done. Carlotto echoes the pessimism of many Italians: 'The law is nothing but a cover for the petty vendettas and back-stabbing of a collection of state spooks.' Italy, he writes, 'has lost any sense of where truth lies'. 'No one cared about knowing the truth,' says the narrator of Marcello Fois's The Advocate. 'It was easier that way, it didn't tread on the toes of important people.'

The criminal cases in many of these gialli have been settled before the action begins. The narrative isn't about closing, but about reopening a case, reinterpreting it. Camilleri's world-weary Sicilian detective, Montalbano, invariably has to battle against his superiors' desire for a quick 'archiving' of a case; in The Colombian Mule the detective is hired not to put someone in prison, but to get him out. In The Advocate, a peasant has been found guilty in absentia and only a dogged lawyer can get him off. Most Anglo-Saxon detective fiction is concerned with justice: the Italian version tends, more interestingly, to focus on injustice. In all these thrillers evidence is deliberately lost, witnesses disappear, there is political interference and the Mafia code of silence - omertà - is observed. 'In a country full of unanswered questions,' Lucarelli said in an interview with La Repubblica recently, thrillers 'have an ever more passionate and numerous public'.

In all this, Carlotto and his colleagues are the inheritors of a noble tradition. Loriano Macchiavelli, Leonardo Sciascia and Fruttero and Lucentini have all managed in the past to combine absorbing plots with meditations on the state of the nation and its susceptibility to illusion. Sciascia in particular understood what his fellow Sicilian Pirandello called the 'marvellous torment' of ambiguity. Moral labels like 'honourable' and 'gentleman' are attached all too loosely in Sicily, and Sciascia toyed with that looseness in his fiction and exported it to the mainland. By now, the suspicion of clear-cut moral distinctions is so deep that whenever an onorevole - an MP - is described in fiction you can be sure he's doing something dishonourable. Once the genie of cynicism was out of the bottle, it became impossible to distinguish appearance from reality or suspicion from paranoia. 'I find you all exhausted from your search to find out who and what other people are,' a character in Pirandello says. This uncertainty makes for sophisticated exercises in detection and carries the fiction far beyond the mere investigation of a crime. As Sciascia has it, Sicilians, like Jews, speak 'by allusion, in parable or in metaphors. It was as if the same circuits, the same logical processes operated in both their minds. A computer of distrust, of suspicion, of pessimism.'

Giallo isn't the right word for these novels: it makes them sound too cheap. The writers themselves prefer 'noir' and there is nothing unreasonable in that. The most self-conscious stylist among them is Lucarelli. In Almost Blue a serial killer is on the loose in Bologna but the police psychologists are bewildered: the killer appears to change identity with each murder. Only the voice remains the same. The hero, Simone, is a blind recluse, who listens closely to sounds and voices:

The sound of a record dropping onto a turntable is like a short sigh, with a touch of dust mixed in. The sound of the automated arm rising up from its rest is like a repressed hiccup or a tongue clucking drily - a plastic tongue. The needle, as it glides across the grooves, sibilates softly and crackles once or twice. Then comes the piano, a dripping tap. Then, the bass, buzzing like an enormous fly at a window.

Mood is modulated by speech patterns, by breathing, sighs and glottal stops. Simone inhabits a synaesthetic world:
Colour comes from the way a person breathes through their words. From the pressure of their breath. If the pressure is low, they're sad, anxious or needy. If the pressure is high, they're sincere, ironic or good-natured. If the pressure is even, they're either indifferent or conclusive. If the pressure increases all of a sudden, they're threatening, vulgar or violent. If the pressure fluctuates and gets rounded out on the corners, then they're being affectionate, malicious or sensual.

One night Simone hears something sinister and contacts Detective Inspector Grazia Negro, and the two attempt to trace a single voice in the 'two thousand square kilometres' of the Bolognese metropolis.
'All I ever wanted was to be a blues singer,' says Carlotto's private eye, the Alligator. His is a Chandleresque world in which gruff good guys return home at sunrise, probably still wearing suits and trilbies. They smoke and drink too much, their relationships are falling apart. The Alligator is a nightclub owner whose nickname comes from his favourite drink: 'seven parts Calvados to three of Drambuie . . . a lot of ice and a slice of green apple to chew on once I've emptied the glass. It's called an Alligator and was invented by a barman in Cagliari, to add a little joy to my life.' The society represented is pretty sordid. Political idealism is a thing of the past. 'The left has been marginalised for good,' Carlotto writes wistfully. 'It's not our world any longer. For a brief moment, we held it in the palm of our hand. Then they snatched it away again.'

The case revolves around a Colombian cocaine smuggler stopped at Venice airport. The police let him go and track him in order to capture his Italian contact, and duly arrest an art smuggler, Nazzareno Corradi, who has rushed to the drug smuggler's hotel after an anonymous phonecall has told him that his Colombian girlfriend is there and seriously ill. The defence lawyer calls the Alligator in to help establish Corradi's innocence. His actions are hampered by the moral code of the underworld: no grassing and all that. In order to find out who the real contact was he needs to uncover the channels used by the smugglers and so tries to buy and offload his own stash of coke. The trail leads not to the criminal underworld but to the police. All the good/ bad roles are reversed. Religious statues from South America are containers for coke. Prison guards are co-operative, given the right amount of alcohol and a few compliant women. The moral is that it's better to be an honest crook than a bent copper. Carlotto is grinding his axe, but it doesn't really matter. He is too much of a realist to allow the release of Corradi, a criminal who is, on this occasion, innocent. The case is solved but the real crooks remain at large.

Camilleri's Inspector Salvo Montalbano is a good cop, and his novels are more giallo than noir. They come with glossaries: every page is peppered with Sicilian dialect that the average Italian struggles to understand. There's a lightness of touch in his descriptions, an almost playful tone, even though, as with Sciascia, the crimes often involve the political class. In several recent interviews Camilleri has attacked Berlusconi and his Sicilian cadres, and that hostility seeps into his fiction. 'In Sicily,' he writes, echoing Lampedusa, 'and in the province of Montelusa in particular, mutatis mutandis - or zara zabara, to say it in Sicilian - things never budged, even when there was a storm on the horizon. He quoted, with obvious facility, the prince of Salina's famous statement about changing everything in order to change nothing.'
Camilleri writes shrewdly about Italian society, from its obsession with food - 'as they ate, they spoke of eating, as always happens in Italy' - to the vertiginous cynicism of the Communist broadcaster who nurtures a scandal not by exposing it but by remaining ostentatiously silent. 'Let me explain, my innocent friend. The quickest way to make people forget a scandal is to talk about it as much as possible, on television, in the papers and so on. Over and over you flog the same dead horse, and pretty soon people start getting fed up . . . if, on the other hand, you hush everything up, the silence itself starts to talk, rumours begin to multiply out of control until you can't stop them any more.'

Like Camilleri, Fois is interested in the character of the place he comes from, in his case Sardinia, and the way in which it is misunderstood by outsiders. Set in the aftermath of the Risorgimento, The Advocate takes place as the island is being colonised, having modernity imposed on it by people from the mainland. A peasant is accused of stealing sheep and murdering the farmer; everyone is already convinced of his guilt. Only a poor lawyer, Bustianu, is prepared to identify the real murderers. The book has the narrative minimalism of a biblical parable, yet this Sardinia is a barren, godless land; the landscape is the 'sole divinity':
And behold me again, pierced to the heart by such a wealth of beauty, and stunned by it, all but overcome. The immensity of it is beyond words: immensity battering at frailty! A sublimity that catches you in the heart . . . I take a deep breath and feel that all that blue light, that green, and the rolling stubblefields, make their secret way into my body and stream lines of poetry into my mind. Words like deep breaths and lips that tremble when my eyes light upon such colours. For this land is to me both my joy and my torment. It lures me to it yet thrusts me off. And I curse it, I curse even while I worship it. O cruel woman, embracing mother, insatiable love!

Everything appears yielding and yet forbidding, all eloquence is a form of reticence and silence. The task of the advocate is to persuade the peasants to share their knowledge with him. In Fois, the detective is usually the last to know; like the murdered man, he is a victim of the plot. That, presumably, is why these books have been so successful in Italy: they chime perfectly with the average reader's (often justified) paranoia. They re-create the conspiracy of silence but manage, in whispered hints, to talk over it.
Tobias Jones, a former editorial assistant at the LRB, is the author of the bestselling Dark Heart of Italy.

… which is now available in Italian as Il cuore oscuro dell’Italia, published by Rizzoli in 2004.