In police work, the M.O., or "modus operandi," refers to the methods the criminal uses to perpetrate the crime. Typically a serial criminal uses the same or similar methods for every crime; the criminal's M.O. entails the planning, execution, escape and other details involved in the crime.
Identifying the M.O. of a criminal helps police connect crimes, identify suspects and create psychological profiles of criminals. An M.O. is typically distinct and characteristic of a specific individual criminal or suspect. For example, the way that a criminal enters the scene of a crime or approaches a victim remains their M.O. for subsequent crimes. Modus operandi is Latin for "method of operation."