Horizontal Gaze Nystagmus Test
One of the more unnerving field sobriety tests is called the Horizontal Gaze Nystagmus test. Moreorless the officer will get close to you face to face and require you to track his finger while they observe the movements of your eye.
The suspect is instructed to stand with their feet together and their arms at their sides. The DUI suspect must follow a stimulus with their eyes only, and they are not to move their head when tracking the stimulus. The stimulus is usually a pen or light held 12 to 15 inches in front of the DUI suspect slightly above their eyes. The police officer must first determine if the DUI suspect is a proper candidate for the test. The police officer will check for equal pupil size and will check for equal tracking of the stimulus with a series of passes from the suspect's left to right. If the DUI suspect cannot track the stimulus it may be an indication of a medical disorder or blindness. If the pupils are not of equal size this may indicate a head injury or that the suspect has ingested a heavy narcotic. An experienced police officer will request backup at this point. If either event is present the test should not be conducted.
Lack of Smooth Pursuit
The test begins with the police officer checking for Lack of Smooth pursuit. The stimulus will be moved in a quick steady pace from the suspect's left to right. This action occurs twice. The police officer is looking for the eye to make "jerking" movements as they follow the stimulus. The DUI suspect will not be able to see this, but the individual conducting the test can see this phenomena. If nystagmus is found it is recorded with a check-mark in the police report for whichever eye it was present.
Distinct Nystagmus at Maximum Deviation
During this portion of the test the officer will move the stimulus to a point where the DUI suspect's eye cannot move in that direction any further. The white of the eye will not be showing. The stimulus is held at this position for four seconds. The officer will look for "jerking." This is done twice for each the left and right eye.
Onset of Nystagmus Prior to 45 Degrees
During this segment of the test the officer will move the stimulus in the same manner it is moved during Lack of Smooth Pursuit. However, the speed of the moving stimulus is significantly reduced. It should take four seconds to move the stimulus from the nose to the left shoulder or right shoulder depending upon which eye the officer is evaluating. If the police officer detects nystagmus while moving the stimulus out to the shoulder, the officer must stop and see if the nystagmus persists. If the nystagmus persists the findings are recorded in the police report. If the nystagmus stops the officer must continue to move the stimulus toward the shoulder.
There are a total of six clues. Each eye is evaluated with the three tests. If the DUI suspect triggers four clues the police officer interprets this as a "failed" test. Most Washington State Courts only allow the HGN evidence to establish consumption of alcohol.
Do not think you can detect whether or not your eyeballs are moving in a jerking fashion; you CANNOT. Field sobriety tests are voluntary and this is one test you definitely want to refuse. Most police officers are "trained" to administer this test once. Most police officers get lazy and or cannot differentiate between natural phenomena that can cause the eyeball to jerk or other factors that can cause this reaction. Do not allow a test that should be administer by a medical professional land you in handcuffs.