An appeal-to-expertise argument creates a presumption for its conclusion when the expert is genuinely an expert in the relevant field and made the claim in a professional capacity

to be the scheme for the appeal-to-expertise kind of argument,[8] then there will be a question for each premise: Is \(E\) really an expert in \(S\)? Did \(E\) say \(p\) when s/he was acting in her/his professional capacity? (… or did s/he blurt it out while drunk at an association party?). If the answer to both questions is Yes, then the argument creates a presumption for the conclusion—but not a guarantee, for the reasoning is defeasible: other information may come to light that will overrid