A recent wave of empirical legal scholarship reports surprising findings about various concepts of legal significance, including the concept of acting intentionally, causation, consent, knowledge, recklessness, reasonableness, and law itself. These studies typically examine laypeople, but often draw broader conclusions about legal experts or law. Findings about laypeople’s (“ordinary”) concepts have been taken to reflect the concepts of trained legal theorists, reveal biases affecting judges’ decision-making, and clarify subtle doctrinal features. This Article questions the validity of such inferences, from empirical findings about ordinary concepts to conclusions about the concepts of those with legal expertise. It presents a case study concerning what it means to act intentionally. An experiment examines the judgments of four populations (N = 774): lay people, law students, non-law students, and United States judges. Legal training affected judgments in three ways, all of which suggest the acquisition of a distinctive legal concept. This case study supports the Article’s broader conclusion: empirical evidence about laypeople’s ordinary concepts does not necessarily carry straightforward legal implications. This defuses provocative empirical challenges regarding biased judging, raises new questions about the relationship between judges and juries, and provides a broader proof of principle: The acquisition of legal concepts is an under-studied but central form of legal expertise.