In the US if a staement is made with honest belief in their truth on a matter that is in the piblic's best interest (acts by the government for example) are good defenses to a claim of defamation, and that is even if the statements made are logiaclly hard to beleive, if a reasonable person could onestly entertain such an opinion, the statement is protected.
In the UK English law allows actions for libel to be brought in the High Court for any published statements which are alleged to defame a named or identifiable individual or individuals in a manner which causes them loss in their trade or profession, or causes a reasonable person to think worse of him, her or them. Allowable defenses are justification (the truth of the statement), fair comment (whether the statement was a view that a reasonable person could have held), and privilege (whether the statements were made in Parliament or in court, or whether they were fair reports of allegations in the public interest). An offer of amends is a barrier to litigation. A defamatory statement is presumed to be false unless the defendant can prove its truth. Furthermore, to collect compensatory damages, a public official or public figure must prove actual malice (knowing falsity or reckless disregard for the truth). A private individual must only prove negligence (not using due care) to collect compensatory damages. In order to collect punitive damages, all individuals must prove actual malice. (Wikipedia)
The 1964 case New York Times Co. v. Sullivan, however, dramatically changed the nature of libel law in the United States by establishing that public officials could win a suit for libel only if they could demonstrate publishers' "knowledge that the information was false" or that it was published "with reckless disregard of whether it was false or not". Later Supreme Court cases dismissed the claim for libel and forbade libel claims for statements that are so ridiculous to be clearly not true, or are involving opinionated subjects such as one's physical state of being. Recent cases have addressed defamation law and the internet.
The four (4) categories of slander per se are (i) accusing someone of a crime; (ii) alleging that someone has a foul or loathsome disease; (iii) adversely reflecting on a person’s fitness to conduct her business or trade; and (iv) imputing serious sexual misconduct (especially the chastity of a woman). Once again, all you would have to prove is that someone had published the statement to a third party. No proof of special damages is required.