The Italian film director and scriptwriter Sergio Citti, who has died aged 72, was particularly associated with the output of Pier Paolo Pasolini, who described him as his "lexicon of the Roman dialect", though he also did noteworthy work on his own account.
He was credited as "collaborating on the dialogue" of Pasolini's first two films, Accattone (1961) and Mamma Roma (1962), and from La Riccotta, one of the four episodes of RoGoPaG (1962; the other directors were Roberto Rossellini, Jean-Luc Godard and Ugo Gregoretti), onwards was assistant director on most of Pasolini's films. He continued in this role even after he had become a director in his own right in 1971, filming Ostia, a script that Pasolini had written, but decided not to direct himself. Citti directed one more film of his own in the early 1970s, and eight more after Pasolini's death in 1975.
Sergio and his younger brother by two years, Franco, had been born and grew up in one of those sleazy Roman slum districts, the borgate which Pasolini liked to explore and to write about. The Citti brothers belonged to the sub-proletariat, those outside the legitimate working classes, though both of them worked as house painters with their father.
After Pasolini's death, Sergio would say: "If I hadn't met Pier Paolo I'd have probably ended up as a delinquent." His close relationship with Pasolini, who he first met in the early 1950s, took some time to develop: Pasolini had already published poetry, was writing his first novel, Ragazzi di Vita (Real Life Kids, 1955), and was grateful for a closer introduction into the Citti world, while Sergio was happy to widen his horizons, helping Pasolini on scripts for directors like Fellini and Mauro Bolognini which had characters who were Roman pimps, whores and petty thieves, or just layabouts.
When in 1961 Pasolini felt the time had come to write and direct a film of his own, it was Federico Fellini's new production company, intended to help young filmmakers, that took an interest in the project. Fellini commissioned a sort of directorial "screen test". Sergio recalled how joyfully Pasolini had set out for the Citti territory, where they would find locations and "actors".
The resulting footage was evidently too naive for Fellini's taste and he declined to back the film. Another producer took over the project, and Sergio's brother Franco was the obvious choice to play the title role in Accattone.
The Citti brothers were launched on professional careers, Franco as actor (destined to play in more than 40 films) and Sergio as assistant, gradually being credited with a more openly creative role, so much so that in 1969, when Pasolini was engaged in preparing his version of the Euripides play Medea with Maria Callas (on which Sergio had begun to collaborate), his mentor entrusted him instead with directing Ostia (1970).
Though Pasolini's many biographers barely mention this film, it was a script that reflected much of Pasolini's existential anguish at the time. Most of the film was shot around the very desolate area of the Roman beaches at Ostia, where the writer was to meet his come-uppance six years later. Citti did a competent job in filming it with his brother Franco playing one of two Accattone-type petty criminals (the other was Laurent Terzieff, whom Sergio himself would dub), but he couldn't give the story the autobiographical depth that it might have had if Pasolini had directed it himself.
Sergio Citti's talents as a director-auteur were to be seen at their best in films which reflected his own semi-serious view on life, typical of Roman popular culture and with a humour rarely present in Pasolini's own works. His second film, Storie Scellerate (Bawdy Tales, 1972), was much better received by the critics. Franco Citti and Pasolini's impish friend Ninetto Davoli played lecherous young men in 19th-century papal Rome.
He was to collaborate on the screenplay of Pasolini's controversial last film, Salò (Salo, or the 120 Days of Sodom, 1976), which had originally been his idea, but did not follow the shoot. In 1977 he wrote and directed a contemporary bawdy film, Casotto (Beach Hut) in which his brother was one of several stars (including Jodie Foster) playing cameos of bathers undressing and having fantasies, shot entirely inside a beach hut.
In the following years he directed and wrote films with many famous stars, among them Vittorio Gassman, Philippe Noiret, Malcolm McDowell and Harvey Keitel. These confirmed his talent for inventing grotesque characters and situations and filming them with a lively visual taste. In later years he won plaudits for his 1997 film I Maghi Randaggi (The Roving Magi) which had a genuine Pasolini feel about it, a semi-blasphemous fantasy about false prophets.
Sergio Citti undoubtedly had naif talents and was an offbeat independent filmmaker who might have been recognised as an Italian Jim Jarmusch if his work hadn't been so closely connected to Pasolini's memory. In Rome, however, he is remembered affectionately by all who knew him well.
However, there was some surprise at the intensity of his angry outburst in May this year - by which time he had hearing difficulties and was confined to a wheelchair - when learning about the confession in a TV programme by Pasolini's presumed killer, Pino Pelosi, who after 30 years declared for the first time that he hadn't been alone that night in the field near the Ostia beach.
Sergio would say he had always thought that Pelosi had been used as bait for a personal or political vendetta. He even put forward a tale that the others involved in the killing had been preparing a robbery from a Rome laboratory of reels from Pasolini's last film. But Pasolini's cousin and literary executor Nico Naldini maintained that the case of the stolen reels had been solved long before that tragic night. A new enquiry was opened by the magistrates, and both Citti and Pelosi were questioned, but on the very day that Citti died, the magistrates announced that there was not enough evidence to re-open the case, and it has been archived.
Both Sergio and Franco married Swedish women named Anita. Sergio's wife was the one who was able to cope longest with the brothers' disorderly home life before she, too, returned to Sweden. Franco survives Sergio, as does their sister Adriana.
· Sergio Citti, film director and scriptwriter, born May 30 1933; died October 11 2005