This text looks at psychology and investigation which draws upon a range of psychological principles relevant to the conduct of criminal or civil investigations. The issues covered by the area relate to the management, investigation and the ensuing legal outcomes of criminal cases. The issues examined reveal that what fuels the investigative process is the information upon which sequences of decisions are made. A basic example would be matching fingerprints found at a crime scene with a suspect. However many cases are not this simple, for example a murder scene disarray may infer that it was a burglar who was disturbed in the act. These inferences will either result in a decision to seek further information or to select from a possible range of actions including the arrest and charging of a potential suspect. This text looks at three psychological processes that may be of relevance - assessing the accounts of the crime, making decisions upon this information and developing an understanding of the actual actions of the offenders themselves.