Use of horizontal gaze nystagmus as a part of roadside sobriety testing.

Alcohol is a central nervous system depressant that can affect eye movement control. Even at low blood alcohol concentrations (BAC's) smooth pursuit eye tracking can be lost and horizontal nystagmoid movements become apparent at relatively small angles of lateral gaze. Law enforcement officers across the nation are being taught evaluation techniques to use these eye movement signs as an indicator of alcohol intoxication. Information obtained at the Ohio State Highway Patrol (OSHP) course on the Advanced Detection, Apprehension, and Prosecution of subjects suspected of driving a vehicle while intoxicated is presented here including the testing and scoring techniques of the horizontal gaze nystagmus sobriety test.