The advancement of multimedia and communication systems has not only provided faster and better communication facilities but also facilitated easier means to organized crime. Concern about national security has increased significantly in the recent years due to the increase in organized crimes, leading to increasing amounts of data available for investigation by criminal analysts. The opportunity to analyze this data to determine patterns of criminal behavior, monitor, and predict criminal activities coexists with the threat of information overload. A large amount of information, which is stored in textual and unstructured form, contains a valuable untapped source of data. Data mining and text mining are two key technologies suited to the discovery of underlying patterns in large data sets. This chapter reviews the use of text mining techniques in crime detection projects and describes in detail the text mining approach used in the proposed ASKARI project.