THE gun used in the murder of former IRA commander Gerard 'Jock' Davison was part of a shipment smuggled into Dublin by an international crime gang, police have revealed.
The senior detective leading the murder investigation told the Irish News that police are following a definite line of enquiry regarding the weapon used in the attack.
Detective Chief Inspector Justyn Galloway said PSNI had joined forces with An Garda Siochana in a bid to trace the rare Marakov handgun used in the murder.
Davison (47) was shot dead as he walked to work at a community centre at Welsh Street in the Markets area of south Belfast on May 5.
Police ruled out dissident republican or loyalist involvement in the attack. It is believed that the murder may have been a grudge killing linked to Davison's IRA past.
Last month the murder featured as part of a BBC Crimewatch appeal which police said got "a decent response".
Mr Galloway, who revealed between 40 to 60 detectives were working on the case, said: "The weapon is relatively unusual for Northern Ireland.
"They are more common in Dublin, so that's a definite line of enquiry. We are as a result working with gardaí on that, " he said.
The development came as it also emerged that the murder of Davison led to the collapse of a major IRA membership trial, after one key witnesses said they "no longer had an appetite for the case to proceed".
The prosecution were forced to offer no evidence in the case against senior republicans Padraic Wilson and Sean Hughes after a number of witnesses withdrew their evidence.
Yesterday, Barra McGrory, director of the Public Prosecution Service, insisted he did not accept "that there was anything the PPS could have done which it didn't do in the prosecution of the case"...
He said it was "regrettable" that the case had collapsed "after the murder of an individual".
"One of the withdrawal statements made clear that the murder of Jock Davison was a factor in no longer having an appetite to proceed," Mr McGrory told the Stormont justice committee.
Hughes, of Aghadavoyle Road, Jonesborough, Co Armagh, and Wilson, of Hamill Park, Belfast, were facing charges including IRA membership and addressing meetings to encourage support for the IRA.
The meetings were alleged to have been part of an internal IRA investigation into the murder of father-of-two Robert McCartney, who was killed by IRA members outside a Belfast bar.
Robert McCartney's sisters were identified yesterday as witnesses in the case which collapsed last week, after reporting restrictions were lifted.