On the evening of 30 September 1975, a resident of Via Pola in Rome heard the muffled cries of a woman coming from the boot of a parked white Fiat and called the police. When they arrived and opened up the boot of the car, they discovered Donatella Colasanti, 17, bloodied and battered, but alive. Beside her was the dead body of her friend Rosaria Lopez, 20. Both had undergone hours of torture before Lopez was finally drowned in a bath. Colasanti had escaped the same fate only by playing dead.

The day before, the girls had accepted an invitation to the sea at S. Felice Circeo from three young, attractive and seemingly trustworthy men Gianni Guido, Andrea Ghira and Angelo Izzo. Neofascists with a superiority complex, the men had other plans for the girls from Romes working-class suburbs. They subjected Lopez and Colasanti to a violent two-day ordeal at Ghiras villa before bundling their bodies into the boot of the Fiat. Look how well these dead girls are sleeping, Colasanti heard one of the men saying. They drove back to Rome and had gone to get pizza when the police were called. All three men received life sentences, although Ghira managed to escape abroad. His grave was supposedly found in Spain last year, although until her death from cancer last December, Colasanti maintained that Ghira was alive and well in Rome.

However horrific they may be, after a while most crimes that fill the front pages largely disappear from public memory. But an exhibition devoted to the cronaca nera of Rome at the Museo di Roma in Trastevere dusts off such forgotten tragedies, showcasing 17 violent and brutal crimes committed in the capital between 1945 and 1991. The murders of the famous, such as Pier Paolo Pasolini and Aldo Moro, rub shoulders with those of people who became household names only through death, like Simonetta Cesaroni, stabbed 29 times in her office on Via Poma in 1990, or Wilma Montesi, found on the beach at Ostia in 1953.

The Italian media has never shied away from the graphic shot, and here too the stories of the capitals crimes are illustrated by stark and shocking images from police and press archives. Smiling back at you are the faces of the dead alongside crime scene photos showing them slumped on the floors of offices, homes or Roman pavements, sometimes covered with a sheet but often not. The photos that stick in the mind are those of bullet holes and bloodstains, of Maria Martirano Fenaroli, strangled to death in a summer dress on her kitchen floor in 1958 on her husbands orders, and of the swollen face of Colasanti, taken in the same moment the police opened the boot of the white Fiat in Via Pola.

There is no doubt that this is an intriguing exhibition, extensively researched and thoughtfully presented, but it also raises some uncomfortable questions. The public has always been simultaneously shocked and fascinated by horrific crimes and the motives behind them, but is morbid curiosity reason enough to turn real-life tragedy into a museum showpiece? And is putting the handiwork of murderers on display turning it, in the process, into art of a sort going a step too far?

Its possible to tell the story of a city and its evolution through its crime news, argues Gianni Borgna, head of the culture department of the city of Rome, who conceived the exhibition. As an example he cites the murders of jewellers Gabriele and Silvano Menegazzo, shot in 1967 in one of the first robberies to be committed with firearms in the city. An incredulous Roman public initially put the blame on armed bands from Milan before having to accept the changing face of crime in the capital.

However, by filleting the bare facts of each crime from newspaper archives, the exhibition misses the opportunity to chronicle the way in which both crime reporting itself and public opinion have changed over the last 50 years. Once, the murder of a prostitute would have been big news; now it takes up three lines in the paper if theres room, comments journalist Enzo Rava, a consultant on the exhibition and author of Roma in Cronaca Nera, published some 20 years ago. People have become immune to tragedy and crime, the reason being that they have access to all the fictional crimes imaginable on television and video.

It could be argued that the exhibition contributes to this desensitisation, compressing years of personal horror and grief into a 60-minute tour. While it brings to mind the names of long-forgotten victims, it makes a sterile and macabre memorial. The images of the murderers themselves, most of whom you would not be able to pick out of a crowd, are in some ways more disturbing. Often crimes are motivated by passions we all have inside us but most of us manage to control, Rava notes. But perhaps the real lesson to be learnt from the exhibition concerns the competence of the police over the years: many of the crimes on display remain unsolved.

Roma in Nera. I Grandi Delitti tra Cronaca, Storia, Costume,

Museo di Roma in Trastevere, Piazza S. Egidio 1b, tel. 0682059127.

10 Feb-2 April. Tues-Sun 10.00-20.00.