The Fairview Heights Police Department's Criminal Investigations Division supports the other divisions of the department by conducting follow-up investigations of reported criminal activity and if warranted presenting cases to the St. Clair County States Attorney's office for prosecution. Detectives review preliminary investigations conducted by patrol officers and then interview victims, witnesses, and suspects. Personnel assigned to the unit posses special knowledge and skills in interviewing, crime scene processing, interpersonal communication, and constitutional issues such as search and seizure. Detectives within the division are members of the St. Louis Metropolitian Major Case Squad.

The division is comprised of a Division Commander, Detective Sergeant, eight sworn officers and a secretary. Four of the officers serve as detectives investigating general criminal activity that has occurred within the city of Fairview Heights. One officer serves as the juvenile detective primarily investigating crimes and civil matters involving persons under the age of seventeen.  Three officers are on special assignment with outside law enforcement agencies. One officer is assigned to the St. Clair County Drug Tactical Unit and another is assigned to the Metropolitian Enforcement Group of Southwestern Illinois.  Both agencies investigate street level drug crimes that occur within a multi-county area. A third officer is assigned to the Drug Enforcement Administration Taskforce.  The Taskforce investigates drug offenses that are of such a nature that they fall under federal jurisdiction.