In the state of California, defamation is a complex area of law confounded by California's Anti-SLAPP statute (C.C.P. §425.16, et seq.), which the California Legislature enacted after it determined that "there has been a disturbing increase in lawsuits brought primarily to chill the valid exercise of the constitutional rights of freedom of speech and petition for the redress of grievances." If you have been sued for a defamation related claim, there is a possibility that you might be entitled to file a special motion to strike certain causes of action. If you prevail in the motion, you will be entitled to attorney's fees and costs early in your case. However, the availability of bringing the special motion is time sensitive.
Conversely, if you are contemplating bringing a lawsuit based on defamation, the merit in your claim depends on the existence of privilege(s) that might or might not attach to the circumstances. A thorough analysis relating to the content of the speech, i.e., what you believe was unlawfully spoken and/or written about you, must be conducted to determine whether or not an absolute and/or a qualified privilege exists. Statements made by judicial officers and prosecutors made in the course and scope of dispensing their duties are absolutely privileged.
Many reports to law enforcement agents regarding the perpetration of a crime are protected. However, liability is factually sensitive. If another person has wrongfully reported to law enforcement that you have committed a crime AND you were actually prosecuted for that crime AND you were acquitted or the case was dismissed on the merits, you might have a case in malicious prosecution against the person who made the report to law enforcement.
In another instance, if a person made an UNTRUTHFUL statement of FACT about you to a THIRD PERSON through spoken or written word and that provable false statement of fact would tend to lower your reputation in your community, you might have a case against that person in defamation.
Furthermore, the Internet has permitted many individuals to perpetrate permanent defamatory statements on a world wide basis. There are remedies for this conduct as well as defenses in both federal and state law, for example the Digital Millennium and Copyright Act of 1998 (DMCA) and the Communications and Decency Act of 1996 (CDA). These laws relate to the Internet Service Providers (ISP), the defamatory, illegal and/or infringing content that appear on websites and the rights and obligations relating to the posting/publishing of certain material.