In pre-modern European societies the responsibility for identifying offenders – as with other aspects of policing – fell directly upon the population. Contemporaneously, the range of agencies engaged in investigative work is striking.

Diverse though the practices of investigation are, they tend to be focused upon establishing the veracity of claims about past practices or incidents, to determine culpability and identify responsibility.

As with other aspects of police work the conduct of police investigation is an area where popular, media-generated, conceptions can be misleading. Perhaps the prime misconception is that the primary purpose of criminal investigations is to establish the identity of the culprit.

Reasons for investigation include bringing offenders to justice, to serve the interests of victims and witnesses, reassuring the community, recovering assets, gathering intelligence, disrupting criminal activity and reducing crime.

Concerns about differential standards of justice applying in the conduct of private and public investigations have been noted in relation to fraud investigation and private security companies: historically, private investigators have been associated with corruption and abuse of power.

Police investigations occur in the immediate aftermath of an incident: this primary investigation is largely concerned with establishing the ‘solvability’ of the crime. A secondary investigation might follow: primarily to gather material for the preparation of criminal charges. A third form of investigation is that undertaken by specialist detectives, including those carried out proactively to monitor known offenders.

The supervision of investigation is conducted along different lines across different jurisdictions. In England and Wales the Crown Prosecution Service functions inde­pendent of the police but does not formally supervise police investigations. In Scotland the Procurator Fiscal is the public prosecutor and also plays a role in directing police investigations.

Police investigative interviews are directed at victims and witnesses, suspects, the public and covert sources of intelligence. Surveillance targets human subjects and technical sources such as phone and video data. Witnesses are sought via media appeals, house-to-house enquiries, anniversary appeals, and road-checks. All of these can be supplemented through interrogation or intelligence and databases.

The funding, organisation and management of detective work have the potential to influence the conduct and success of investigations as much as technological capacity. Many of the failings associated with high-profile investigations – from the Ripper murders of Victorian London to the racist killing of Stephen Lawrence – have been caused by management failings rather than an incapacity to gather or pro­cess forensic evidence.

Investigations are best understood as dynamic social activity, dependent on the qualities and circumstances of the incident, the social organisation of the police response and the extent to which the system of law constrains or enables resources.

As in other aspects of policing, institutional practices, cultural dynamics, training and resources, and the relation of police to other agencies in the criminal justice sector combine to influence the investigation of crime.