Slander is spoken defamation, and defamation is by definition untrue statements.

So Truth isn't really a defense against a slander allegation; it's a refutation of that allegation. If the spoken words are true, they can't be defamatory, so they can't be slander.

I don't know the fine, legal distinction between a refutation and a defense, but it seems like they're quite close.

https://www.law.cornell.edu/wex/defamation#:~:text=Truth%20i....

You can refute a statement or proposition (which might be an allegation of wrongdoing). You can mount a defense without refuting any allegation; for example, it's usually a defense to any allegation to say that "It wasn't me", without claiming that the event didn't happen.

In the UK, it's usually a defense to say that the act was justified, even if it happened and you did it. I think it's usually a defense to claim that you had no choice.

I suppose my persnickety comment was to the effect that if the claim is true, then there was no slander; you aren't innocent or guilty, because the alleged act simply didn't happen.