The key to catching the killers of a Northern Ireland police recruit lies within the local community, a senior detective has said.
Twenty-five-year-old Ronan Kerr died four years ago when a bomb exploded under his car in Omagh, Co Tyrone.
No-one has been convicted of the murder but the officer leading the investigation is confident the dissident republican extremists could still be charged.
Detective Chief Inspector Una Jennings, from the PSNI’s Serious Crime Branch, said: “Although a significant amount of progress has been made, the key to putting people before a court charged with Ronan’s murder lies with local communities in Omagh and east Tyrone.”
Constable Kerr, a Catholic and Gaelic games enthusiast, was killed as he left his apartment at Highfield Close in Omagh at about 3.45pm on Saturday April 2 2011.
The newly qualified officer had been on his way to work in Enniskillen, Co Fermanagh.
It is thought he was targeted as part of a violent campaign aimed at intimidating nationalists from joining the PSNI.
The death sparked widespread revulsion from both sides of the sectarian divide and politicians from all sections of the community attended his funeral where, for the first time, GAA players formed a guard of honour alongside PSNI officers.
The young officer’s family are still struggling to come to terms with their loss, Ms Jennings said.
“Ronan’s murder is as devastating for his family today as it was four years ago.
“Their pain remains so devastating that they feel unable to talk publicly about their plight on the fourth anniversary.”
As part of the large-scale and complex investigation mounted in the wake of the murder, 8,203 items have been seized; 15,539 individuals have been spoken to; 12,754 investigative actions have been generated and 122 house, vehicle and land searches have been carried out.
Eighteen people have also been arrested and one person has been jailed for weapons offences linked to the wider probe, police have revealed.
The bomb attack has been linked to a number of other incidents including the attempted murders of two PSNI constables in Castlederg, Co Tyrone, in 2008 and Randalstown in 2010.
In both cases the policemen suffered serious injuries.
And, the same dissident republican gang is believed to have planted a bomb at the headquarters of the Northern Ireland Policing Board which scrutinises the work of the PSNI in 2009.
Ms Jennings said: “From the early days of the investigation, we said this was going to be a long-term inquiry with Ronan’s murder at its core but incorporating several linked incidents including attempts to murder other police officers, a bomb attack, arms finds and armed robberies.
“It has proved to be an extremely large investigation but one which still has the potential to be concluded by charging suspects.”
Anyone with information is asked to contact detectives in Serious Crime Branch at the Maydown police complex in Co Londonderry on the non-emergency number 101.