Potential sources of observer bias in police observational data

Much of our knowledge about police behavior "on the street" is based on in-person observation of the police. However, little research has examined how the observers can potentially bias observational data. In this paper, anecdotal accounts from a variety of field settings are categorized into four potential sources of observer bias. Secondary analyses of data from a large-scale observational study of police are used to assess the impact of three out of the four type of observer bias (reactivity, going native, and burnout). There is evidence of reactivity for arrest, but not use of force behavior and little support for going native and burnout. More generally, observer bias is categorized as: (1) threats to the validity of observational data collected at different stages of fieldwork; and (2) the potential for human error implicit in observational data. The incorporation of a semi-structured field diary is suggested to more systematically document all four types of observer bias in future research.