In ordinary language, a crime is an unlawful act punishable by a state or other authority. The term crime does not, in modern criminal law, have any simple and universally accepted definition, though statutory definitions have been provided for certain purposes.Criminal investigation is an applied science that involves the study of facts that are then used to inform criminal trials. A complete criminal investigation can include searching, interviews, interrogations, evidence collection and preservation, and various methods of investigation.crime is an unlawful act punishable by a state or other authority. The term crime does not, in modern criminal law, have any simple and universally accepted definition, though statutory definitions have been provided for certain purposes.While criminal justice and criminology are certainly related fields, they are not identical. Criminology is the study of crime and deviant behavior. Criminology is an interdisciplinary field in both the behavioural and social sciences, which draws primarily upon the research of sociologists, psychologists, philosophers, psychiatrists, biologists, social anthropologists, as well as scholars of law