Skip to main content

Policing - Crime Investigation


Part 3 of the Policing sector of the Criminal Justice Assessment Toolkit, produced by the United Nation Office on Drugs and Crime in close co-operaiton with the Strategic Police Matters Unit of the OSCE Secretariat.


A fair and effective criminal justice system, an integral part of which is crime investigation builds public confidence and encourages respect for law and order. In essence, crime investigation is the process by which the perpetrator of a crime, or intended crime, is identified through the gathering of facts (or evidence) – although it may also involve an assessment of whether a crime has been committed in the first place. Investigation can be reactive, i.e. applied to crimes that have already taken place, or proactive, i.e. targeting a particular criminal or forestalling a criminal activity planned for the future.

There are two basic approaches to managing crime investigation. In some, typified by jurisdictions with a civil law tradition, the responsibility for an investigation is given to a prosecutor or judicial officer, such as a juge d’instruction or “investigating judge”. Where this is the case, investigators work under the instruction and management of the prosecutor and/or investigating judge and, indeed, there may even be a special law enforcement agency designated as “judicial police”. In the second approach, often found in jurisdictions with a common law tradition, investigations are conducted by the police more or less independently of prosecutors until the case, and the charged suspect, is handed over for prosecution in the courts. There are, however many variations within both basic systems. For example, in many common law jurisdictions, prosecutors work closely with police investigators for at least some types of crimes. No matter what the system, basic tenets remain the same: identifying who committed the criminal act and gathering sufficient evidence to ensure a conviction.

In many civil law models, there are often two phases described in the investigative process: the preinvestigation or intelligence phase and the investigation itself. Usually the police will be wholly responsible for the pre-investigation (which seeks to identify whether an offence has actually been committed and to gather basic information) after which a prosecutor will assume control. In the come countries, including those based on a common law model, there is no such phased approach; with the term “investigation” applying to the entire process beginning the moment in which a crime first comes to notice.