When special criminal investigating units first emerged in Germany in the late 1900's, they responded to scientific advances in criminology, increased sophistication of the criminals, and the growing rights of the accused. Although the West German criminal police (as well as their counterparts, Scotland Yard in England and Surete in France) have substantially added to the safety of the population, The reformers of NW argue that the new policy will boost local morale and improve collaboration between detectives and local police. However, the only systematic study of the two police branches shows that no major collaboration problems exist. The other reformist argument that many offenders commit crimes in their area of residency and are, therefore, more familiar to local police fails to convince because only 15 percent of offenders commit their crimes locally. Having local, all-around police officers investigate criminal cases slights the special skills of criminal investigators: providing evidence which holds up in court, identifying unknown offenders, arresting known offenders, crime prevention, and the protection of witnesses.