Classification: An Overview of Selected Methodological Issues

Classification methods have two fundamentally different but related goals. The first is to build new classifications. The second is to assign unknown cases to existing classifications. Many traditional offender criminological classification systems are of questionable value, partly because of confusion concerning purposes and roles of classification. The link between purpose and method has recently become more important because of the emergence of a vast range of quantitative methods. The multidisciplinary origins of these methods have meant that some of their embedded concepts and logic may be inconsistent with criminological theory or data. No single method is best for all purposes. Used correctly, new methods may dramatically upgrade the quality of our classifications. A framework for creating and validating classifications in criminology is urgently needed. The framework should include interacting stages for choosing a content domain, constructing the classification, checking internal validity, and establishing external validity.