noun
principal offender; perpetrator
Legal term for the person who directly commits a crime, as opposed to an accomplice or accessory.
この事件の正犯者はまだ逮捕されていない。
The principal offender in this case has not been arrested yet.
犯人 is a general term for a criminal or culprit; 正犯者 specifically refers to the principal offender in a legal context.
Compound of 正 (principal) + 犯 (crime) + 者 (person). A straightforward legal term.