Since the 1960s, police services seek support of psychologists on a variety of matters in policing and law enforcement, especially on the selection and well-being of their staff (Yuille, 1992). Psychology as a science and the profession of psychologists went through very dynamic developments over the past decades. It is also clear every year that psychology is becoming increasingly more relevant for the police services and law enforcement in Europe. Over this time span the relationship between police services and psychologists has seen dynamic fluctuations. The progress of cooperation was by far not linear, and it took efforts from both professional sides so that today psychological know-how is not only fully accepted within police services but also seen as an important element in the landscape of police science. This development required to a certain degree a change in the cultures of policing. Some stereotypes of old-fashioned “tough cop cultures” have been almost hostile against psychologists discussing their emotions.