Defamation: the publication of a statement that tends to lower a person in ther estimation of right-thinking members of society generally; or that tends to make them shun or avoid that person;
Where was the
publication?
Slander: defamation of a transient form - a statement spoken or conveyed in a form that is not lasting - eg, a gesture of speech.
A one on one (or two) conversation is not slander. A report to the police if you think a crime is or has been commited
cannot be construed as slander. Otherwise imagine the dilemma when a murder suspect is found to be not guilty, they would have a remedy under law by your logic and could sue!