When a crime has been committed and reported or discovered, it must be investigated. In most instances, the police handle much of this stage too, although it is often a specialist detective branch of the police. But criminal investigators may also be members of other government agencies or work for the prosecutor’s office.
Countries differ on their policies towards the recruitment of detectives. In some countries, especially the English-speaking nations, detectives are almost exclusively selected from the ranks of serving uniformed police officers. Once transferred to the detective branch it is usual to remain in it for the rest of one’s career. Many countries, however, consider that the skill set needed to be a detective is completely different from that needed to be a uniformed patrol officer and generally recruit directly from suitably qualified civilians, usually from a higher social class and therefore better educated. Other countries operate a hybrid system, recruiting both directly and from suitable uniformed officers. Usually detectives are able to reach the senior ranks, even in countries where ordinary policemen generally cannot, although senior detective officers may also be directly recruited and sometimes are police officials transferred to the detective branch with no previous experience of detective work.
One thing that is common to most police forces outside the major cities, however, is a lack of detectives. In this era it is rare for a detective to ever be seen in a rural area or small or even medium-sized town. Almost all cases will be handled by uniformed officers. Detectives from a force with national or regional authority may be called in if the case is really complex, but local police commanders will often resist this even if they know very well that they do not have the skills or resources to handle the case, as it is seen as an unwelcome encroachment onto their territory.