This book is the first in a series of four intended to establish a foundation of knowledge concerning what we know about effective policing in free societies. The goal of the series is to promote a common understanding that will influence the practice of policing worldwide. In all, the series is comprised of the following works: Policing for a culture of lawfulness. Accounting for police performance. Community engagement and police problem solving. Using information to cure crime and violence. While it is the intent of the authors that the books of the series be used as a collection on modern policing, each book is able to stand alone to support a course of study on its specific topic.