Modus operandi in criminal investigation and prosecution

Modus Operandi always thought "M.O." stood for method of operation, but actually it stands for a Latin term, modus operandi. I wasn't far off, though. According to "The 'Lectric Law Library's Lexicon," modus operandi means "way of operating. A term often used in police work, abbreviated "m.o.," referring to the particular way a certain criminal performs his criminal act" (http://www.lectlaw.com/def2/m133.htm).Answers.com defines the term as "mode of operation" (http://www.answers.vom/topic/modus-operandi).

When a criminal is prosecuted, the district attorney does not have to prove how the crime was committed, but it could help the case if he can show the modus operandi and that the accused person committed other crimes in the same way. The other crimes would not have to be identical to one the criminal is accused of, but a similarity would have to be shown. Usually, the prosecutor brings it up only if peculiar or distinctive means are used. For instance, in the Jon Benet Ramsay case, the child was killed with a homemade garrote in the basement of her own home and struck on the head with a blunt object that fractured her skull. That would be a distinctive modus operandi. In a robbery, on the other hand, in which the robber brandished a pistol and demanded cash and valuables, the modus operandi would not be distinctive because lots of robberies are committed that way.

Modus operandi can help investigators understand how a criminal thinks. For instance in the Ramsay case, the killer may have been a sadistic pedophile who got a thrill from making his victim suffer before she died. Thus, the police would know they were dealing with a sick individual who is liable to do it again. If another child murder, committed in a similar fashion, took place and the police caught the person, they might have a good chance of solving the Ramsay case as well. The M.O. could lead them to check DNA samples, for instance. A database for modus operandi could be very helpful.