The mere tendency of speech to encourage unlawful acts is not a sufficient reason for banning it. The government “cannot constitutionally premise legislation on the desirability of controlling a person’s private thoughts.” Stanley v. Georgia, 394 U. S. 557, 566 (1969). First Amendment freedoms are most in danger when the government seeks to control thought or to justify its laws for that impermissible end. The right to think is the beginning of freedom, and speech must be protected from the government because speech is the beginning of thought.
— Anthony Kennedy, Associate Justice of the Supreme Court of the United States (1988-Present). Ashcroft v. Free Speech Coalition, 535 U.S. 234, 253 (2002)

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. More importantly however in California, Civil Code§47 was amended in 2020 and made effective in 01 January 2021 to add subsection (b)(5) establishing an exception “This subdivision does not make privileged any communication between a person and a law enforcement agency in which the person makes a false report that another person has committed, or is in the act of committing, a criminal act or is engaged in an activity requiring law enforcement intervention, knowing that the report is false, or with reckless disregard for the truth or falsity of the report.” The amendment is a huge departure from prior California law that absolutely protected persons from defamation-related civil court lawsuits for damages for knowingly making false reports to law enforcement about criminal activity. The amendment supersedes Hagberg v. California Federal Bank FSB, 32 Cal. 4th 350, 7 Cal. Rptr. 3d 803, 81 P.3d 244 (Cal. 2004). In a defamation claim relating to statements made in a police report, a Hawai’i United States District Court held that

“[T]he court concludes that under Hawaii law an absolute privilege does not apply to complaints made to police. The court declines to apply the minority rule suggested by [defendant] that communications in a police report are absolutely privileged. Given this ruling, the court will apply existing Hawaii law, which holds more generally that, for claims of defamation, a speaker is protected by a qualified privilege when he or she "reasonably acts in the discharge of some public or private duty, legal, moral, or social, and where the publication concerns subject matter in which the author has an interest and the recipients of the publication a corresponding interest or duty." [T]he qualified privilege is conditional and it must be exercised (1) in a reasonable manner and (2) for a proper purpose. The immunity is forfeited if the defendant steps outside the scope of or abuses the privilege. The [*13] qualified privilege may be abused by (1) excessive publication, (2) use of the occasion for an improper purpose, or (3) lack of belief or grounds for belief in the truth of what is said.” (Tuomela v. Waldorf-Astoria Grand Wailea Hotel (D.Haw. Jan. 22, 2021, No. 20-00117 JMS-RT) 2021 U.S.Dist.LEXIS 12634).)

In another instance, if a person made an UNTRUTHFUL statement of FACT about you to a THIRD PERSON through spoken (slander) or written (libel - can also be a video or sound recording) words and that are provably false statements of fact and that 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 to perpetrate permanent defamatory statements on a worldwide 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 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.