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What does "Modus Operandi" Mean?

Tricia Christensen
Updated: May 16, 2024

Modus operandi, in a legal sense, can be best translated as a way of doing something. It is also called an M.O., and most people may be familiar with this term from the many legal or police dramas, where it is used repeatedly. Typically, modus operandi in legalese refers to a similar pattern of doing things when someone is suspected of committing multiple crimes. If the suspect has committed the crimes in the same way, it becomes easier to prove all of them, even if the only link between some of the crimes is the way they were committed. Individual jurisdictions determine specific evidence required to charge people with auxiliary crimes, and a strong M.O. argument is not always sufficient evidence, but it certainly may be evidence enough to further investigate a crime and get warrants or other permissions to question, search or seize property to make a case.

Probably the most common examples of modus operandi are used when serial killers are investigated. Many of them have specific habitual behaviors that they will employ when committing crimes. In essence they leave a trail of hints that they’ve committed the same type of crime through highly ritualized behavior. This is how criminal investigators are able to link one crime to another, and in doing this, they may also be able to cast the net further, looking at other criminal acts that appear to be similar and that might warrant investigation. Alternately if the person has not been caught, determining modus operandi may lead to clues about the killer’s identity.

Even when crimes are not so severe, trying to discover modus operandi can be useful in apprehending a criminal, getting arrest warrants, or prosecuting a case. The average criminal who is not a serial killer is still likely to do some things the same way, even if he or she tries to cover it up. For instance, in the movie Home Alone, one of the thieves insists on flooding the sink each time he robs a house. This little “way of doing things,” connects him and his partner to a number of crimes where the sink is intentionally flooded in a house that has been burglarized. M.O. is not always so straightforward or purposeful, but analysis of evidence may discover patterns previously unnoticed.

It is not always easy to prove modus operandi because behavior discovered must be unique. Saying, “Well, he carried a gun when he robbed the bank,” isn’t uncommon and wouldn’t be much of a strong M.O. On the other hand, if the criminal carried a gun while sporting a rubber duck on his head, the M.O. gets a little more interesting. Usually it takes several distinctive properties to make a strong case that a person may have committed a number of crimes of the same nature.

MyLawQuestions is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Tricia Christensen
By Tricia Christensen
With a Literature degree from Sonoma State University and years of experience as a MyLawQuestions contributor, Tricia Christensen is based in Northern California and brings a wealth of knowledge and passion to her writing. Her wide-ranging interests include reading, writing, medicine, art, film, history, politics, ethics, and religion, all of which she incorporates into her informative articles. Tricia is currently working on her first novel.
Discussion Comments
By Ravellu — On Dec 11, 2013
Modus operandi is Latin. The rough or approximate translation of the term is "method of operation". As stated, the term is most commonly used in police work or criminology, but can be applied to any ritual or system were obvious patterns or repeated actions are used. Examples would be the business practices of a company and how they interact with clients or staff or the policies and practices of organizations like the Catholic church.
By Authordor — On Dec 10, 2013

Where did the term modus operandi come from?

Tricia Christensen
Tricia Christensen
With a Literature degree from Sonoma State University and years of experience as a MyLawQuestions contributor, Tricia...
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