The president of Sinn Féin, Gerry Adams, issued a warning to the killers of Robert McCartney that "he will not let the issue go until those who have sullied the republican cause are made to account for their action."
He said "self-preservation and selfishness will not prevail in this case".
Mr Adams called for those involved to come forward and take responsibility for the murder.
"Although many people have come forward - others have not, particularly some who may have been directly involved in Robert's murder. In my view these people must give a full account through whatever conduit they chose," Mr Adams said.
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"So far Robert McCartney's killer has not had the courage to do this," he added.