What is the test for “express malice” in libel law?

Malice includes not only the general or popular definitions of that word as denoting ill-will or spite. It includes the question of an improper motive by the defendants. Excessive language in itself is insufficient to establish express or actual malice. The term is generally discussed by Lord Diplock in Horrocks v. Lowe at pp. 669-70 in the following terms: “So, the motive with which the defendant on a privileged occasion made a statement defamatory of the plaintiff becomes crucial. The protection might, however, be illusory if the onus lay on him to prove that he was actuated solely by a sense of the relevant duty or a desire to protect the relevant interest. So he is entitled to be protected by the privilege unless some other dominant and improper motive on his part is proved. ‘Express malice’ is the term of art descriptive of such a motive. Broadly speaking, it means malice in the popular sense of a desire to injure the person who is defamed and this is generally the motive which the plaintiff sets out to prove. But to destroy the privilege the desire to injure must be the dominant motive for the defamatory publication; knowledge that it will have that effect is not enough if the defendant is nevertheless acting in accordance with a sense of duty or in bona fide protection of his own legitimate interests. “The motive with which a person published defamatory matter can only be inferred from what he did or said or knew. If it be proved that he did not believe that what he published was true this is generally conclusive evidence of express malice, for no sense of duty or desire to protect his own legitimate interests can justify a man in telling deliberate and injurious falsehoods about another… “… what is required on the part of the defamer to entitle him to the protection of the privilege is positive belief in the truth of what he published or, as it is generally though tautologously termed, ‘honest belief. If he publishes untrue defamatory matter recklessly, without considering or caring whether it be true or not, he is in this, as in other branches of the law, treated as if he knew it to be false. But indifference to the truth of what he publishes is not to be equated with carelessness, impulsiveness or irrationality in arriving at a positive belief that it is true. … “Even a positive belief in the truth of what is published on a privileged occasion — which is presumed unless the contrary is proved — may not be sufficient to negative express malice if it can be proved that the defendant misused the occasion for some purpose other than that for which the privilege is accorded by the law. The commonest case is where the dominant motive which actuates the defendant is not a desire to perform the relevant duty or to protect the relevant interest, but to give vent to his personal spite or ill-will towards the person he defames. If this be proved, then even positive belief in the truth of what is published will not enable the defamer to avail himself of the protection of the privilege to which he would otherwise have been entitled. There may be instances of improper motives which destroy the privilege apart from personal spite. A defendant’s dominant motive may have been to obtain some private advantage unconnected with the duty or the interest which constitutes the reason for the privilege. If so, he loses the benefit of the privilege despite his positive belief that what he said or wrote was true… “Qualified privilege would be illusory, and the public interest that it is meant to serve defeated, if the protection which it affords were lost merely because a person, although acting in compliance with a duty or in protection of a legitimate interest, disliked the person whom he defamed or was indignant at what he believed to be that person’s conduct and welcomed the opportunity of exposing it. It is only where his desire to comply with the relevant duty or to protect the relevant interest plays no significant part in his motives for publishing what he believes to be true that ‘express malice’ can properly be found.”