In a Western democracy, the police have a number of interrelated roles including preventing crime, preserving public order and detecting criminal offences. The investigation of crimes may be supported by scenes of crime officers (SOCO), who collect evidence at crime scenes, and forensic investigators and scientists who may be employed by the police force or by other organisations. A comprehensive survey of the psychology of policing is beyond the scope of this book. Instead, a selection of topics is presented that illustrate the intersection of police investigations and psychology. There is a discussion of how the collection, processing and interpretation of forensic evidence may be affected by psychological processes. There follows a comparison of ‘standard police interviews’ with psychologically informed alternatives including ethical interviewing and cognitive interviewing. Finally, there is a discussion of offender profiling. Chapter 7 also covers topics of relevance to policing, including the use of aids to suspect identification.