While I have no reason to doubt that it's valid to argue "A || (!A && B)", in this particular case B => !A. When the lawyer brought evidence that he had tried

While I have no reason to doubt that it's valid to argue "A || (!A && B)", in this particular case B => !A. When the lawyer brought evidence that he had tried to verify the information (B), that evidence itself automatically disproves his plead that he didn't think it could be false (A). (Note that didn't have to necessarily be the case: for example, if he had claimed that it was his assistant who asked the verification question, rather than he himself.) So, unless he made the second plead and brought the evidence at a latter time, shouldn't he have just skipped A altogether, and preserved his credibility? (And possibly avoided a perjury charge? IDK if in an American court both claims would be sworn statements)