modus operandi

noun2

1. •
   A person or thing's normal mode of operation.

   • Failing that, if contact was absolutely necessary, a series of thumb jabs to the nerve cluster at the base of the neck would be his chosen modus operandi—quiet as a whisper. — 2001
2. •
   A known criminal's established habits and mode of work when committing specific offences, especially fraud, matched with characteristics of an unsolved crime to narrow down (limit to a specific list) or profile suspects.