perpetrator (n.)Related entries & more
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).
perp (n.)Related entries & more
1940s American English police jargon shortening of perpetrator (as in perp walk).
mens reaRelated entries & more
"state of mind accompanying an act which condemns the perpetrator to criminal punishment," Latin, literally "guilty mind;" from mens "mind," from PIE root *men- (1) "to think."