*puts postgraduate law hat on*
Truth is not an absolute defence to defamation in New South Wales.
It is a defence to the publication of defamatory matter if the defendant proves that—
(a) the matter carried, in addition to the defamatory imputations of which the plaintiff complains, one or more other imputations (contextual imputations) that are substantially true, and
(b) the defamatory imputations do not further harm the reputation of the plaintiff because of the substantial truth of the contextual imputations.
Basically in layman's terms. To use truth as a defence the facts must be well known and not causing further harm to the plaintiff because everyone knows about it.
Secondly. If the publication was delivered with malicious intent. Just about forget about trying to use "truth" as a defence.