modus operandi

Definition from Nolo’s Plain-English Law Dictionary

(mode-us ah-purr-and-eye or ah-purr-and-ee) A criminal investigation term for "way of operating," which may prove the accused has a pattern of repeating the same criminal acts using the same method. Examples: a repeat offender always pretended to be a telephone repairman to gain entrance.

Definition provided by Nolo’s Plain-English Law Dictionary.