This BBC report on the shooting of loyalist hard man Mark Haddock carefully sources all allegations about his activities other than the one for which he is charged to statements made by Labour party leader Pat Rabbitte under parliamentary privilege in the Dail. Hence:
"Mr Rabbitte claimed Mark Haddock ordered the murder of Raymond McCord, 22, who was beaten to death by a UVF gang in Newtownabbey in November 1997.
"He also claimed Haddock had been involved in eight other murders - and said he had not been charged with any of them because he was working as a Special Branch informer who was allowed to act with impunity."
Thus the statements are not about Haddock, but about what someone else said about him, and that other person can't be sued. It'll be important for Rabbitte's sake that nothing he said is perceived as having made Haddock a marked man, although since he was probably just reporting what was already "known" in police and paramilitary circles in Northern Ireland, it's unlikely he was presenting any really new information.
UPDATE: While an almost identically sourced report aired on BBC radio, the report in Wednesday's Irish Times is content with attributing similar allegations to "sources" without the insulation of Rabbitte's speech.