Pierce County DUI lawyer explains what happens during administration of the horizontal gaze nystagmus test

In my experience as a Pierce County DUI lawyer, most people facing DUI charges were subjected to one or more field sobriety tests prior to their arrest. The horizontal gaze nystagmus test is one such test. Here is how the test is supposed to work:

Preparing to Perform the Test

When an officer prepares to give the horizontal gaze nystagmus test, he must first ask the driver to remove her glasses if she is wearing any. Next, he must instruct the driver to put her feet together and place her arms by her sides. The driver must keep her eyes open for the duration of the test.

Checking the Subject’s Eyes

Once the driver is ready to take the horizontal gaze nystagmus test, the officer holds a stimulus, which might be a pen or a light, for example, at 12 to 15 inches in front of the driver’s nose and at eye level. The officer first checks for equal pupil size between the two eyes, and equivalent eye movements. Next, the officer moves the stimulus from side to side — left to right — to check whether the eyes can smoothly track the stimulus. The officer must also move the stimulus sharply to each side and read the eye’s “maximum deviation,” which describes how far the eye can go. If the eye cannot hold its position at maximum deviation or the eye makes jerky movements, the officer must make note of those characteristics when totaling the driver’s test results.

Unlike the horizontal gaze nystagmus test, the vertical version of the test simply requires the driver to follow the stimulus from eye level to as high as possible above the driver’s head while the officer moves the stimulus. If the eyes cannot hold the position or the eyes show a jerky motion, the officer must note those observations.

Help from an experienced Pierce County DUI lawyer

A knowledgeable Pierce County DUI lawyer can educate you about how to challenge the nystagmus test. For example, many factors – e.g., flashing lights, passing traffic, dust, wind or other eye irritants, even fatigue – all may create doubt regarding the reliability of your test results. If you would like me to review the facts of your case, please call 888-394-6997 or submit the Free Case Evaluation form on this page to schedule an appointment.

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