This paper investigates experience effects for public officials. Using a unique data set of companies investigated under UK competition law, we find very strong experience effects for chairman of investigation panels, estimated from the increase in experience of individual chairman. Probit and IV probit regressions indicate that replacing an inexperienced chairman with one of average experience increases the probability of a ‘guilty’ outcome by approximately 30% and after chairing around 30 cases a chairmen is predicted to find almost every case guilty.