The Collaborative International Dictionary of English v.0.48:

Culprit \Cul"prit\ (k[u^]l"pr?t), n. [Prob. corrupted for
   culpate, fr. Law Latin culpatus the accused, p. p. of L.
   culpare to blame. See Culpable.]
   1. One accused of, or arraigned for, a crime, as before a
      judge.
      [1913 Webster]

            An author is in the condition of a culprit; the
            public are his judges.                --Prior.
      [1913 Webster]

   2. One quilty of a fault; a criminal.
      [1913 Webster]

WordNet (r) 3.0 (2006):

culprit
    n 1: someone who perpetrates wrongdoing [syn: perpetrator,
         culprit]