Andrew Allen, 24, died when he was gunned down in his home in Buncrana on February 9th, 2012.
Andrew was murdered by a group of individuals at his home in at Links View Park.
He was shot in front of his partner at approximately 9.20pm and pronounced dead at the scene.
A car believed to be involved in the murder was located on fire at Churchbrea, Fahan which is three miles outside Buncrana shortly after the shooting.
Police on both sides of the border believe Derry-based Republican Action Against Drugs (RAAD) carried out the murder with the assistance dissident republicans based in Donegal.
An Garda Síochána say they are grateful for all the witnesses that have come forward and made statements.
However, Gardai believe that there are still people in both Buncrana and Derry city who have information that may assist with the investigation.
Six people have been arrested and questioned during the course of this investigation with up to 700 lines of enquiry followed over the past 10 years.
A spokesperson said: “An Garda Síochána are grateful for all those who have assisted the investigation.
“An Garda Síochána together with our counterparts in the Police Service of Northern Ireland continue to investigate this heinous murder.
“Now with the passage of time An Garda Síochána is appealing to anyone with information which may assist this ongoing investigation to make contact with them.
“Any assistance received may be instrumental in bringing this investigation to a successful conclusion.
“Anyone with information can contact the incident room at Buncrana Garda Station 074 93 20540 or the Garda Confidential Line 1800 666 111.”
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