In general, all defamation actions (slander is the "verbal" type of defamation, while libel is the written form) require these elements:
(1) a false and defamatory statement concerning another;
(2) publication of the statement, without privilege, to a third party;
(3) fault on the part of the publisher, amounting at least to negligence, in ascertaining whether the statement is true or false; and
(4) special damages.
[Restatement 2d, Torts ? 558]
In California, "defamation" is a "tort" (or "civil wrong") more particularly described as an invasion of your interest in your reputation. It may be "libel" (written) or "slander" (verbal). [Civil Code ? 44; 5 Witkin, Summary 10th (2005) Torts, ? 529] The tort involves (a) a publication that is (b) false, (c) defamatory, and (d) unprivileged, and that (e) has a natural tendency to injure or that causes special damage. [Civil Code ?? 45, 46; Rest.2d, Torts ??558, 559; 5 Witkin, Summary 10th (2005) Torts, ? 529]
Is "Bad Intent" Required?
Because libel and slander are intentional torts, the defendant must have intended the publication. But, malice or actual ill will is not an element of defamation. [5 Witkin, Summary 10th (2005) Torts, ? 529] Typically speaking, you must show that the statements were "factual" statements that were actually false AND that the person making them knew they were false. That knowledge element can be hard to prove at times, if there is any aspect that is true. All this is required is that the person making the statement intended to make it, not that he/she intended to injure someone.
"Opinion" versus "Fact" Statements
Statements made that are merely "opinions" are protected. (For example, there's a difference between saying "I think that guy is a crook" and saying "that guy is a felon." In the first instance you may be stating an opinion, where the 2nd example, if false, could be defamatory.)
The 3rd issue to address is damages: it's often hard to show actual damages resulting from the publication. In any particular case, a party whose reputation has been injured would generally have to show what damages were suffered as a result of the statements, and that usually requires some showing of economic loss. If there are significant, tangible economic losses, you can also recover for the "emotional distress" and the "non-economic" damages to you reputation that was caused by the statements.
Defense to Defamation-Truth
Truth- Truth of the statements made is a complete defense against liability for defamation, regardless of bad faith or malicious purpose. See e.g. Campanelli v. Regents of Univ. of Calif. (1996) 44 C.A.4th 572, 581, 51 C.R.2d 891; Rest.2d, Torts ?581A]
Defense to Defamation-Privilege
Privilege-The Civil Code lists publications that are absolutely privileged. They include those made:
(a) "In the proper discharge of an official duty." [C.C. 47(a)];
(b) "In any (1) legislative or (2) judicial proceeding, or (3) in any other official proceeding authorized by law, [C.C. 47(b)], 5 Witkin, supra, ? 562];
(c) "By a fair and true report in public official proceedings [C.C. 47(d)]; or (d) "By a fair and true report of public proceedings [C.C. 47(e)]
Subject to the above, if the statements made about someone are, indeed, false, that person may have a civil case against the person making the statements (whether they be oral or written), but that person would have to assess what monetary losses were suffered to determine if the case was worth pursuing. Often times, people also have to assess this on a personal level, in terms of how it might look to be involved in a lawsuit, the fact that by filing a complaint that person is often "republishing" the very statements believed to be defamatory and doing so in a publicly accessible place (the Court records), and that you may very well have to "re-live" the embarrassment of those statements.
In the end, if you have any lingering questions about whether to pursue a defamation claim, it is best to discuss all of the facts of the case with a local attorney to assess your chances of success and the scope of your damages claims.
Disclaimer: I am an attorney admitted only in California, so my focus here is on California law. Further, the foregoing guide is designed to be a sort of "general" primer on libel and slander claims that may provide guidance to those with questions on this topic who live in other states. For a more detailed assessment of the topic, or for specific questions related to the state where you live, you are encouraged to speak with local counsel.