This paper analyses police officer perspectives on the seriousness of potential misconduct or unethical behaviour, and the factors that might shape whether they would report their colleagues’ misdemeanours. It compares responses from police officers in UK three forces, looking at potentially corrupt behaviours described in a series of scenarios. The discussion includes why some types of misdemeanour seem more likely to be reported and the potential effects of a newly introduced formal Code of Ethics. In terms of differences between ranks and roles, and different responses from different services, the study suggests that the way police culture operates is significant and needs to be more widely addressed. The study used scenario-based questionnaires to elicit views about the seriousness of certain police behaviours and to ask whether officers would report colleagues’ misdemeanours. It develops a previous survey by one of the authors which conducted a similar survey published in 2005. Using the same questionnaire the new study examined a larger and more diverse sample of serving officers (n = 520). This new study compares responses from police officers in three UK forces, geographically distributed across the country and have differing characteristics in terms of size, rurality, population density and policing priorities.