The Major Case Squad of Greater St. Louis provides investigative services for homicides to the police agencies in the counties of St. Louis, St. Charles, Jefferson, Franklin Warren and Lincoln in Missouri, and Madison, St. Clair, Monroe, Jersey, Macoupin, Bond, Clinton, and Randolph counties in Illinois. The are currently over 500 investigators in Missouri and Illinois who are members of the Major Case Squad.
Currently sixteen members of the Chesterfield Department serve in various capacities with the Major Case Squad. Col. Ray Johnson, the Chief of the Chesterfield Police Department serves as the Chairman of the Squad's Board of Directors; others serve as Deputy Commanders, Deputy Report Officers (second line supervisors), media spokespersons and investigators. Both Chesterfield detectives and patrol officers serve as investigators on the squad. Squad members may be detached from their regular duties to assist other agencies for five to fifteen days depending on the needs of the investigation.
When a serious crime occurs, the Major Case Squad is activated and the investigators are assigned to assist the local police department with the investigation and prosecution of the suspects involved in the case. The Major Case Squad of Greater St. Louis is recognized as being one of the top investigative squads in the United States and has a clearance rate of over eighty percent (80%) on the cases they are involved in.