June 13, 2018 | DUI

Driving Under the Influence & Understanding Field Sobriety Tests: The Horizontal Gaze Nystagmus (HGN) – Post 2

The Horizontal Gaze Nystagmus test should be the first test administered by law enforcement if they follow the instruction and training of the National Highway Traffic Safety Administration standards. Simply stated, this is the eye test. The word Nystagmus means, “involuntary jerking of the eyes”. When performing this test, the law enforcement officer looks at three areas: Horizontal, Vertical and Resting Nystagmus.  The purpose of the HGN test is to cause and observe Nystagmus or involuntary jerking of the eyes. Specific items tested are equal tracking, smooth pursuit, maximum deviation, and onset of angle of nystagmus.

The HGN test on its own, when performed correctly, has been determined to be 77% accurate in determine intoxication. In order to properly conduct the HGN test it takes the law enforcement officer a minimum of 14 passes and 82 seconds.

The NHTSA requirements for administration of the HGN include:

1. Removal of glasses, but not contact lenses.
2. Instructions. The instructions require that the subject place their feet together and hands down by their sides. Also, it is requisite that you be instructed to follow the stimulus, usually a pen or finger, with only your eyes and not move your head. Before the test can begin the subject must acknowledge that they understand.
3. Position of stimulus. The stimulus device, finger or pen, must be placed between 12 and 15 inches away from the subject’s nose and slightly above eye level.
4. Movement of stimulus “Passes”. A pass for each eye is the movement of the stimulus from the center of the nose to the outside limit of that eye and back to center. 14 passes are divided into 4 stages, each eye having two passes for each stage, except the initial equal tracking stage which require only one pass for each eye. The stages include: Equal Tracking, Smooth Pursuit, Maximum Deviation, and Onset angle of Nystagmus.
5.  Equal tracking passes. The equal tracking portion of the HGN is designed to determine if a person has neurological or medical symptoms which invalidate the HGN test. If there is lack of equal tracking the HGN test must stop. This stage should take only 2 seconds to complete.
6. Smooth Pursuit passes. This stage consists of 4 total passes, 2 for each eye, and should take 16 seconds. If the law enforcement officer observes lack of smooth pursuit 1 clue or indicator of intoxications is scored per eye that exhibits lack of smooth pursuit.
7. Maximum Deviation passes. This stage consists 4 total passes, 2 for each eye, and should take a total of 32 seconds. The purpose of this test is to determine if the subject exhibits Nystagmus, or eye twitching, at the furthest angle. If distinct Nystagmus is observed, above and beyond normal nystagmus this is an indicator of intoxication.
8. Onset angle of nystagmus passes This stage consists of 4 total passes and should take at least 32 seconds. The purpose of this test is to determine if Nystagmus onsets before 45 degrees, if it does then that is an indicator of intoxication.
9. 2 passes of vertical nystagmus, which are optional.

Common mistakes made by law enforcement officers conducting the HGN test include:

1. Moving the stimulus too slowly;
2. Moving the stimulus too quickly;
3. Holding the stimulus too far away;
4. Holding the stimulus too close; and
5. Curving the stimulus upward, downward, or around as it is being moved through passes.

The HGN eye test is a well-developed and objective test to help provide indicators as to whether a driver is intoxicated. The biggest problem with it is that many times it is impossible to tell what the officer observed as there is usually no camera giving us the officers perspective of observing how a driver’s eyes reacted in the test. As such, the best way to fight the HGN eye test observations is timing.

If you have been arrested for driving under the influence hire an attorney who is able to obtain a copy of all video of the stop and determine whether the test was performed properly or not. As an attorney if I observe a test have been performed improperly I may require the retaining of an expert to put evidence on to the Court about how the test was improper.