At its most basic, defamation involves making a false statement about someone that damages their reputation.
In more technical terms, “[a] statement is defamatory of a person if it tends to harm the person’s reputation by lowering the person in the estimation of at least a substantial and respectable minority of the community.” This is taken from Instruction 22:8 (Chapter 22) of Colorado’s Civil Jury Instructions (CJI-Civ.). It should be noted that not all nasty or disparaging meet those standards.
First, generally speaking, defamatory statements must be false statements. Though, which side (person suing or person being sued) ultimately bears the responsibility of proving the statements were false or true depends on the nature of the case.
Overall, however, the person sued (also called the defendant) will not be legally responsible to the person bringing the defamation claim (also called the plaintiff) “if the affirmative defense of substantial truth is proved.” “A statement is substantially true if its substance or gist is true. Substantial truth does not require every word to be true.” CJI-Civ. 22:16 (Affirmative Defense—Substantial Truth).
Second, the statements at issue must be statements of fact or opinion statements that imply certain undisclosed (but defamatory) facts are true. CJI-Civ. 22:8, Note 2. This is because “’there is no such thing as a false opinion.” Id. An example of an opinion statement that implies a certain fact is true could be, “In my opinion, Mr. Green is a murderer.” Whether someone has committed murder is a fact, something capable of being proven true or false. Saying “In my opinion” before asserting “Mr. Green is a murderer” can still be the basis for a defamation claim.
Third, defamatory statements are false statements that can do serious harm. They call into question a person’s reputation, professionalism, ethics, or honesty. They are false statements that subject a person to serious contempt, hatred, scorn, and ridicule.
It is always important to look at the full context of a statement to determine if it’s one that is, or could be, considered defamatory. CJI-Civ. 22:10, 22:11.