The expertise paradigm was used in two studies to examine decision-making by rugby referees. Videoclips were used to assess infraction detection and knowledge base, or sources of information used. In Study 1, referees of high and low experience were compared, and in Study 2 referees and players were compared. Analysis by signal detection used a framework to classify types of information. Study 1 yielded no differences in detection of infractions as a function of experience, however, referees of high experience used significantly more sources of information than the group with low experience across all categories of information. In Study 2, there were no significant differences between referees and players, with the exception that referees displayed greater use of episodic memory information in decision-making.