AS GANGSTERS go, Antonio Romeo had more guts than most.

A court has heard that the convicted drug importer had judiciously joined a Griffith organised crime family by marrying Maria Sergi, the daughter of the alleged crime boss Giovanni Sergi, when he decided to risk it all by conducting an affair with the wife of her brother, Tony Sergi.

The last person to have dallied with Tony Sergi's wife ended up with a bullet in his knee.

And Mr Romeo is alleged to have posed threatening competition to his fellow businessman Pasquale Barbaro after Mr Romeo finished serving an eight-year prison term in 2002.

But when Mr Romeo was shot in the back six weeks after his release from jail, despite the large number of people present, there was a shortage of witnesses.

Yesterday in the Glebe Coroner's Court, the magistrate Mary Jerram found that a homicide had taken place but the perpetrator was unknown.

The officer in charge of the investigation, Detective Sergeant Eugene Stek, told the court several people might have had reason to kill Mr Romeo.

"There's two hypotheses: that the deceased's death was caused by the extramarital affair he had with his sister-in-law, Jenny Jolliffe, organised by Giovanni Sergi, the head of the organised crime family in Griffith … [or] that the deceased's death was caused by … Pasquale Barbaro," Mr Stek said.

In the early 1990s Ms Jolliffe had conducted an affair with Rocco Barbaro, who had an accident with his firearm shortly after Mr Sergi had threatened to shoot him in the leg.

"Police enquiries reveal that Giovanni Sergi informed Rocco Barbaro that for his indiscretion … for the Sergi family to save face, Rocco Barbaro had to receive a gunshot to his leg," Mr Stek said.

"Rocco Barbaro did receive a gunshot to his leg on the 5th November, 1993. To this day, Rocco Barbaro maintains that this was an accidental shot as a result of dropping a loaded shotgun behind him, although police inquiries reveal that it was quite impossible for that to happen."