Substantial Truth: "Truth" is an absolute defense to an action for defamation. Even if you are not sure that what you've published is true, you should read this section.
Opinion and Fair Comment Privileges: Statements of opinion generally cannot support a cause of action for defamation, even if they are outrageous or widely off the mark. A defense similar to opinion is "fair comment on a matter of public interest." If the mayor is alleged to be involved in a corruption scandal, expressing your opinion that you believe the allegations are true is not likely to support a cause of action for defamation.
Fair Report Privilege: This very important privilege may apply if you relied on a public document or a statement by a public official for the incorrect information, made clear that the public document or statement was your source, and fairly and accurately used the source.
Neutral Reportage Privilege: The neutral reportage privilege covers unverified accusations made by one public figure about another on a matter of legitimate public interest, such as when a politician who opposes a health care bill says that the bill's sponsor is taking money from the pharmaceutical industry.
Wire Service Defense: If you republish information from a reputable news source (such as the Associated Press) you may be entitled to the wire service defense if it turns out that the information was false.
Statute of Limitations: If the plaintiff has waited too long to file a lawsuit, the defamation claim might be barred by the statute of limitations, which sets the maximum amount of time plaintiffs can wait before bringing a lawsuit after the events they are suing over have occurred.