This study evaluated an existing standardized self-rating scale designed to measure affective, cognitive, and reflective indicators of wisdom through a survey of state-level jurists, an occupational group for whom wisdom has unique importance. The researcher invited the participation of all current and former members of the Missouri State Judiciary (N = 651). After determining that the 258 respondents (40%) comprised a representative sample to the extent that findings were likely to generalize meaningfully to the population, the survey data were used to evaluate the instrument. The instrument demonstrated reliability, in terms of internal consistency, and construct validity, in terms of nomological and known group validity, supporting previous evidence that the instrument measures wisdom, as defined. Within the subscales, issues of content and face validity were identified, suggesting further analyses of data might contribute to subsequent refinement of the instrument. In the demonstration of known group validity, Missouri Jurists' mean scores on each subscale and on the combined-scales overall score were found to be significantly higher than published norms on this instrument, suggesting that the instrument can distinguish a group of persons predicted by theory to be wiser than average (i.e., jurists), from a group predicted by theory to show average levels of wisdom (i.e., adults in the general population). This finding provides the first evidence, albeit preliminary, that Missouri citizens have selected persons with above average levels of wisdom to serve in their state judiciary. Given the inseparability of personal and professional development in adulthood, the findings argue for collaborative study by law and educational psychology of the measurement of wisdom as a conception of adulthood maturity with specific relevance for the judicial profession.