Event-related potential (ERP) of the brain measured at the scalp that has an average latency of 300 milliseconds from stimulus onset and is recorded maximally at site PZ in the International 10-20 System. The P300 is related to unique characteristics of the stimulus and is most often associated with the “oddball” or rarely occurring stimulus. For example, the P300 is known to be evoked by a low incidence auditory tone that is of a different pitch than another tone that is occurring much more frequently. A P300-based Concealed Information Test has been developed for criminal testing, though field testing is incomplete. See: Farwell & Donchin (1991); MacLaren & Taukulis (2000); Rosenfeld (1998).