This third edition is designed as an introduction to research methods in criminal justice techniques. The detailed information that is generated by research is a management tool that has become a significant part of criminal justice operations. The text discusses the purposes, process, and uses of research that focus on identifying what information is already known about a particular topic or question.  Ethical issues in criminal justice research are reviewed, as is investigating the validity and reliability of crime data sources. Also offered is an introduction to research design--the plan or blueprint for a complete research project. The principles of sampling are thoroughly discussed as is survey research, a common form of gathering information in the criminal justice setting. A review of the concept of scaling and some common methods of scale construction are introduced.  Additional major topics include qualitative interviews and observational studies in qualitative research, as well as a wide variety of research techniques that comprise evaluation research. The definitions and examples provided in the book will help students and practitioners to both comprehend research articles and reports and to conduct their own research. Each of the authors brings specific areas of expertise to the text, and they are familiar with the research process and have worked together on several published studies. The text is designed primarily for persons with little or no research background and provides real-world examples and clear definitions of terms and concepts.