Earlier quoted context omitted.
It seems pretty fucked up that if I’m being defamed, I can’t do anything about it if the person defaming me is mentally ill. Do I just have to sit there and watch my reputation go down the shitter, with potential loss of jobs, income, etc.? That doesn’t seem like a workable system to me.
In the US, you're not being defamed until someone relates a damaging false fact. This particular defendant has, apparently, only said that the Tarot deck told her the plaintiff was a murderer. That's not a fact. It's like saying "in my opinion, you're a murderer". You're allowed to do that.
It may well be a fact. But it's a fact about the Tarot cards, not the professor. I don't think the case would be materially different if the cards required less interpretation, e.g. if she had instead consulted a Magic 8-ball which told her the professor was the murderer "without a doubt".