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Read it. But... won't we then be unable to jokingly shout "aaaah, you're Mafia!", but Ar will still be able to say all sorts of things that don't fit into the category of "based on my information, etc."? He didn't say he knew for sure; he said that checking him would be pointless. And this can be interpreted as an attempt by a Mafia member to avoid being checked, rather than revealing information available to him.