Deterrence theory describes a process of offender decision making that consists of two linkages—one in which official sanctions and other information affect a would-be offender’s perceptions about the risks of criminal conduct, and another in which such perceptions influence the decision whether or not to offend. Decades worth of empirical research has concentrated virtually exclusively on this latter linkage, and in so doing, has produced an incomplete account of the deterrence process. This article develops a model of how perceptions of sanction certainty are modified in response to an individual’s involvement in criminal activity and the consequences (if any) therefrom. Implications of the model are tested with data from a multi-wave, panel survey of 1,530 high school students from the southeastern U.S. Key findings include: the manner in which new information affects perceived certainty depends on the level of perceived certainty before the new information is received, and the extent of peer offending was one of the most influential factors in determining change in perceived sanction certainty over time