If a crime is committed in a city other than Detroit, officers from that city or the Michigan State Police will respond by investigating the offense. In the City of Detroit, officers are separated into districts (southwest, eastern, western, etc.) and units (such as homicide or auto theft). If, for example, the crime was committed in the southwest district of the city the officers from the second and fourth prescient will respond. If the scene is a homicide, officers from that unit will also respond to the scene. Officers can either be called to a location or a victim will contact police officers to report a crime.
In Wayne County, a Detective, Sergeant, or Lieutenant who handles the district or specific class of crime committed will be given the task of interviewing witnesses, collecting statements, and reviewing other physical evidence in order to begin to answer the age old question of who committed the criminal offense and possibly why the person did it. The officer charged with these duties will become known as the Officer in charge of the case (OIC) and will also be the one responsible for communicating with the Assistant Prosecuting Attorney (APA) who will prosecute the case. Once the information is obtained and a suspect is identified the OIC will then take the warrant to the Prosecutors Office and seek issuance of a warrant against the suspect. The APA assigned to the case will depend on the type of crime alleged.
Under rule 6.102(A) an arrest warrant must be issued by a court if presented with a proper complaint and if the court finds probable cause to believe the accused committed the alleged offense. A complaint is merely the written accusation that a named or described person has committed a specified criminal offense and must include the substance of the accusation along with the name and statutory citation of the offense. Rule 6.101(A). Simply put, the APA must file a document stating what a person allegedly did and what criminal offense that action violates. Once a court finds that the suspect probably did it, the police can then arrest that suspect for the allegation.