Witnesses and victims often choose not to report crimes to police. Previous research suggests that decisions to report and participate in the criminal justice process are the product of a complex, multi-determined confluence of cognitive, social, and cultural factors. The focus of this dissertation was to examine the relationship between attitudes regarding the legitimacy of police, expressed willingness to report crimes, and actual crime reporting. Study 1, conducted with 309 undergraduate students, was designed to assess whether the relationship between perceptions of legitimacy and expressed willingness to report varied depending on the specific crime conditions. The results showed that when presented with broad, hypothetical questions that do not specify the crime conditions (i.e., the typical method used in willingness studies), individuals imagine their own crime scenarios. Willingness to report varied depending on the specific conditions imagined and based on explicitly defined features of the crime. The legitimacy-willingness relationship was robust, regardless of whether respondents imagined the crime features or they were explicitly provided with them. Study 2 assessed attitudes about the legitimacy of police and crime reporting behavior among 75 undergraduates who had either been a witness or victim of a serious crime within the previous two years. Attitudes about the legitimacy of the police were strongly associated with respondents' expressed willingness to report crimes to the police, but were not associated with actual crime reporting behavior. Expressed willingness was strongly associated with actual crime reporting. The results underscore the importance of social factors associated with actual reporting. Specifically, victims and witnesses were less likely to report crimes when: (a) they were committed by perpetrators they knew; (b) they perceived the crime as not serious; (c) they did not fear retaliation; (d) they feared being labeled a "snitch;" (e) they did not talk to a parent or co-witness after the crime occurred; and, (f) they did not perceive crime reporting as a moral duty. Implications for process-based theories of control, police practice and procedure, and future research are discussed.