Term of the Day
Alcohol Gaze Nystagmus
Definition - What does Alcohol Gaze Nystagmus mean?
Alcohol gaze nystagmus occurs when an individual's eye begins to twitch involuntarity when looking at or following a certain object. Because alcohol has a slowing affect to human senses and body functions, during alcohol gaze nystagmus, the eyes twitch due to trying to "catch up" with the object they are following, or to try to focus on the fixated object. Officers often look for this trait in an individual who is suspected of being under the influence of alcohol while driving.
How Officers Identify Alcohol Gaze Nystagmus
The test officers use to identify alcohol gaze nystagmus is called a Horizontal Gaze Nystagmus Test, or HGN Test. During a traffic stop of a suspected drunk driver, an officer would ask the individual behind the wheel to step out of the vehicle. The subject's eyes must be seen clearly by the officer, should remove glasses, and should not be facing oncoming headlights. The officer would then turn on a penlight, and ask the driver to follow the light with their eyes, keeping their head straight forward. During the test, an officer attempts to identify three indicators:
- If the eyes move smoothly or jerk involuntarily
- If the eyes jerk when moved to the side as far as possible
- If the eye jerks before moving through a 45 degree angle
Because alcohol can affect a person's peripheral vision, a driver who exhibits alcohol gaze nystagmus will experience a twitching in the eye that is trying to focus on a moving object. According to the National Highway Traffic Safety Administration, HGN tests are:
- Very accurate if administered properly, and the officer has gone through HGN training
- Has scientific support in its effectiveness to identify Alcohol Gaze Nystagmus
- Administered by officers in many states, but not all states