modus operandi

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A Latin phrase meaning “mode of operating.” In criminal law, modus operandi refers to a method of operation or pattern of criminal behavior so distinctive that separate crimes or wrongful conduct are recognized as the work of the same person. Modus operandi is used as a basis for admitting evidence of other crimes and is permitted by Rule 404(b)(2) of the Federal Rules of Evidence. For example, in a case involving the armed robbery of a bank, evidence that the alleged robber was convicted of an armed robbery one year prior would be admissible to prove identity through modus operandi where in both the prior case and the current case the perpetrator wore a purple cowboy hat, possessed a gold gun with mother of pearl handles, was heard humming the tune to “Twinkle Twinkle Little Star,” and put the money in a black Gucci bag. The evidence is so specific that it uniquely identifies defendant as the perpetrator in the case at hand.

[Last updated in July of 2020 by the Wex Definitions Team]