perp (n.)

1560s, "one who commits or has committed," literally "the one who did it" (in English usually an evil act), from Late Latin perpetrator, agent noun from past-participle stem of perpetrare "to perform, to accomplish" (see perpetrate). Fem. forms are perpetratress (1811, of Nero's poisoner Locusta); perpetratrix (1862, in reference to Charlotte Corday).