There can't be, because "jerk" is a subjective assessment, and defamation requires a statement of fact. The "falsifiability" rubric Rayiner has been using is helpful. I'm not a lawyer, but I read lots of defamation lawyers, and note that you can further extend the requirements for defamation:

* It's (apparently, in many circumstances, consult lawyer) not defamation to relate your interpretation of facts already on the record. In other words, it's often not defamation if you're simply wrong about something, so long as you're not relating your wrongness in a manner that would lead a reasonable person to think you're authoritative for your claim. "Based on a bunch of stuff I read in the paper, Gibson's has a history of racial profiling" might be a much safer thing to say than "as faculty and administrators of Oberlin College I'm informing you that Gibson's has a history of racial profiling".

* If the injured party is a "public figure", you have to do more than prove a falsifiable false statement that causes actual injury; you also have to prove malicious intent, meaning that the speaker knows that what they're saying is false, and is saying it specifically in order to harm someone.