Justification or truth: You have to prove, to a legal satisfaction, that what was published was true. The problem is that if the defence fails, aggravated damages may be awarded. The law takes the view that if you plead truth and cannot prove it, you are persisting in a lie and may do more harm to the plaintiff's reputation.

Fair comment: You must prove that the comment was made on a matter of public interest, that what was published was comment, not fact, and that the comment was fair in being honestly held. The judge will decide the public interest. Comment is the expression of opinion, whereas fact is the statement of verifiable information.

Privilege: You can't sue for anything said in either house of the Oireachtas; this extends to committees, but not to witnesses. Also for fair and accurate court reports, if published contemporaneously.