Although no charges have been brought in any of the murders, detectives believe recent developments could lead them to important new information in several of the investigations. When the murders occurred this time last year, they marked an unprecedented increase in the frequency of gangland murders.

Friday will be the first anniversary of the murder of both Hughie McGinley, the Sligo Traveller shot dead in front of his partner and infant daughter, and of former Westies gang figure Anthony Glennon, who died in his car at Clonee, Co Meath, when a group of men fired the contents of several handguns into the vehicle.

Their murders occurred in the middle of one of the bloodiest months in underworld crime, when half a dozen young men were shot dead between the middle of April and mid-May. The shooting dead of Joseph Rafferty on 12 April last year by a man with connections to the Provisional IRA kicked off a bloody four-week period in which more people were killed in gangland murders than in the whole of 2002.

The frequency of the gun murders led to a political storm which has not abated.

Commentators and political opponents seized on the words of justice minister Michael McDowell, who had described the killing of criminal Paul Cunningham six months earlier as ?the sting of the dying wasp". The minister's handling of the crisis has remained under a critical spotlight since.

Two days after Rafferty was slain, drug dealer Terry Dunleavy was shot dead outside his girlfriend's flat at Croke Villas near Croke Park. The following week, over a space of two days, Glennon and McGinley were murdered. A week later, on 5 May, Mark Byrne was shot dead as he walked up Berkeley Road having been released from Mountjoy prison.

Byrne had been nearing the end of a sentence for drugs offences and was on day release. Gardai are investigating the possibility that his death was related to a dispute with a former prison inmate. One man closely connected to the suspected murder was recently arrested after a garda surveillance operation on suspected ATM robbers.

On the day of his killing, Byrne walked from the prison into Berkeley Road.

Moments after leaving the Selections shop, where he bought mobile phone credit, he was shot three times in the head. He staggered across the street before collapsing in front of the Mater hospital. He was pronounced dead at the scene.

The gunman was seen running down Berkeley Road in the direction of the city centre before turning right into Sarsfield Road and making his escape. Gardai are investigating the possibility that Byrne's killer was a known criminal from Ballymun exacting revenge for a knife attack on him by Byrne.

The shooting of 22-year-old Martin Kenny was one of the most brutal. He was shot dead in front of his girlfriend in her house at Ballymun Parade in the early hours of 14 May. The killer smashed in the front door and ran up the stairs and then shot the young man dead in bed. Described as a ?nice young fella" by neighbours, Kenny was not a major criminal figure and was known to gardai only in relation to what have been described as ?minor issues".

The killing of Joseph Rafferty on 12 April at his home at Ongar, west Dublin, allegedly by a man with close links to the IRA, bore a striking resemblance to the murder of Belfast man Robert McCartney the previous January. While Rafferty's family have travelled to the US to obtain high-level support for their campaign to bring the killer to justice, there has been some development in a parallel investigation into a series of alleged burglaries at the Rafferty family home and an assault against a member of the victim's family.

It is believed Rafferty was told several times prior to his death by members of a family with whom he had become involved in a dispute that he would be targeted by the Provisional IRA. The mother of the family with whom Rafferty was in dispute is in a relationship with a former member of the IRA. He is the only suspect in the murder.

The dead man's family has since established the Justice for Joe campaign aimed at bringing Rafferty's killer to justice. They believe that, due to the chief suspect's connection to the IRA, the Sinn Fein leadership has done little to convince the suspect to give himself up.

On St Patrick's Day, Rafferty's sister Esther Uzell and family representatives were invited to the White House to meet US president George Bush. On a previous visit to the US in February they also met US special envoy for Northern Ireland Mitchell Reiss. In Dublin they have met the US ambassador James C Kenny and representatives from the Independent Monitoring Commission (IMC). In a report last February, the IMC noted that ?a member or former member of PIRA may have been involved" in Rafferty's murder.

While no charges have been brought in the murder of Hughie McGinley, gardai have made 20 arrests and seized several items relevant to the investigation. The victim was shot as he sat in a parked van in the centre of the town on the afternoon of 28 April last. The fatal shots were fired by the pillion passenger of a motorbike which pulled up alongside him and quickly sped away. The killing was widely believed to have been linked to an ongoing feud between two Sligo families.