To define crime and criminal psychology. Before we go on to consider the work of the criminal psychologist, let us first consider, what exactly is crime? You may think you know the answer to that, but as with most things, it is not as simple as we might first think. Definitions of Crime In psychology, there are three theories that are the most widespread approaches to defining crime. There are other approaches, but as these are the most widely accepted, we will consider those here !