A person intentionally publishes a defamatory communication when that person knows that it is false. A person negligently publishes a defamatory communication when a reasonable person under the circumstances would not have published the communication. It is an absolute defense to a claim of defamation that the alleged defamatory statements were substantially true at the time the statements were made. Substantially true statements are not defamatory. The publication doesn't have to be absolutely or mathematically true.
Substantial truth is all that is required.
See also Philadelphia Newspapers, Inc., v. Hepps, U.S. Supr. In the absence of contrary evidence, the law presumes that the plaintiff, at the time any defamatory statements were made, enjoyed a good name and reputation. But a person with this privilege may not abuse it. There are four general claims for invasion of privacy. The question is whether a reasonable person in similar circumstances would find the conduct very objectionable or would be expected to take serious offense to it.