King County DUI attorney explains the “Horizontal Gaze Nystagmus” sobriety test

King County law enforcement may ask drivers to perform a variety of field sobriety tests during DUI stops. The “horizontal gaze nystagmus” test is one of those tests. In my work as a King County DUI attorney, I explain this test to my clients as follows:

Type of sobriety test

Police can ask motorists to perform standardized or non-standardized field sobriety tests. Standardized tests have developed through research and evaluation by the National Highway Traffic Safety Administration. The horizontal gaze nystagmus test is a standardized test.

Definition of nystagmus

“Nystagmus” is a term describing rhythmic eye movements, also known as oscillation. Although most people experience nystagmus, normal oscillation is only a slight motion. These eye movements are involuntary and sometimes result from a disturbance of the inner ear. In general, a person cannot completely eliminate nystagmus in the eyes. Oscillation due to impairment or intoxication, however, may become more pronounced or frequent, or occur at an increased degree angle. The “horizontal gaze nystagmus” is a specific type of movement that describes a lack of smooth pursuit in the eye movement and identifies the angle of onset.

Factors that may affect eye movement

Factors such as wind, flashing lights, dust, dirt or other eye irritants can affect a subject’s eye movements. In addition, physical conditions, illness, age, use of over-the-counter medications, or caffeine consumption might also affect a driver’s eyes. Any of those factors might weaken the reliability of your nystagmus test results.

Contact me

If the prosecution plans to present evidence of the results of your horizontal gaze nystagmus test, you may benefit from the counsel of an experienced King County DUI lawyer. I would be happy to meet with you for a free initial consultation. Please submit the form on this page or call me at 888-394-6997 to schedule an appointment.

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