The role of police in a democracy is the part that the police are expected to play in a democratic society. The relevant literature shows that there are three major sources of expectations concerning what the police should do and how they should do it: the police organization, the law, and the public opinion or the environment. When expectations from the three sources are compatible, there is minimal difficulty in deciding what the police should do and how they should do it. The purpose of this study is to explore, through empirical approach, the content of expectations from the three sources. After analyzing and comparing the empirical data collected in this study, the role of the police in democratic society is clearly decided and the evidence-oriented policy advice is also provided to solve the conflicts about the role of police.