An example of modus operandi in criminology is when a first-time burglar breaks into a house by entering from the roof, and then continues to use the roof as an entry point in subsequent break-ins. The term modus operandi is more commonly known by its acronym, M.O.
In criminology, an example of modus operandi could be that all the victims of a certain serial killer are blond, blue-eyed and tall. Another example is a serial rapist who waits at shopping malls at night and then forces single women into their cars at gun point.
The modus operandi is a form of learning called operant conditioning. Operant conditioning is a system of learned behaviors that are either reinforced or changed due to consequences. For example, the evolution of the modus operandi could either be in response to increased efficiency, as the criminal becomes better at committing his particular crime, or to overcome a previously non-existent obstacle.
Another element of a criminal's modus operandi is the "calling card." The calling card is an aspect of a crime that is not necessary to the committal of the crime itself. For example, a murderer may pose his victim's body in a certain arrangement. Criminal behaviorists believe that these calling cards reveal certain psychological characteristics about the offender.