In the current research, the author investigates the influence of social categorizations on retributive emotions (e.g., anger) and punishment intentions when people evaluate suspected offenders as independent observers. It is argued that information that guilt is certain or uncertain (i.e., guilt probability) has different consequences for retributive reactions to ingroup and outgroup suspects. In correspondence with predictions, results of four experiments showed that people reacted more negatively to ingroup than outgroup suspects when guilt was certain but that people reacted more negatively to outgroup than ingroup suspects when guilt was uncertain. It is concluded that guilt probability moderates the influence of social categorizations on people's retributive reactions to suspected offenders. © 2006 by the Society for Personality and Social Psychology, Inc.