The patrolling officer requires a substantial amount of professional knowledge in order to be able to act in an appropriate way. A lot of this professional knowledge takes the form of so called “tacit” knowledge and may be hard to describe in such a way that a new recruit will be able to absorb it simply by reading a text. Highlights of the 30 different types of knowledge identified in this study include: (1) using the skills of other police officers; (2) to prioritize cases and use the available resources effectively; (3) to form a suspicion; (4) to get an informant and interact with an informant; (5) dealing with mentally ill and unstable persons; (6) to mediate a peace and solve problems; (7) to act preventively; (8) to convey a serious message; (9) safety thinking; (10) to debrief an event; (11) to use different communication aids; (12) conducting a technical investigation; (13) balancing between common sense/ethics and legislation; (14) finding an offender; and (15) presenting a case to decisionmakers. This study was based on participative observations, more than 6,000 hours of observation, and 2,000 interviews with police officers involving all 21 police districts in Sweden. The purpose is to illustrate different forms of professional knowledge that is desirable for a police officer to possess. The results provide an understanding of both the police officer’s complex work practice and the need to identify and describe the professional knowledge this work requires. References