Michigan (HGN) Horizontal Gaze Nystagmus Test

There are three standardized field sobriety tests that are administered by Michigan law enforcement agents: horizontal gaze nystagmus, the walk-and-turn test, and the one-leg stand test. These tests are used to determine whether a driver is under the influence of alcohol and if a DUI/OWI arrest can be made.

Nystagmus is an involuntary twitching, or jerking, of the eye. The idea is that someone under the influence of alcohol and/or drugs has a more pronounced nystagmus.

To administer the test, the police officer will ask you to stand with your arms at your side and your feet together. You will then watch a stimulus, such as a penlight or the officer’s finger, with eyes while keeping your head still. Before the test, the officer should have asked if you understood the directions and if you wore contact lenses.

There are three things that a police officer is looking for during the horizontal gaze nystagmus test. The first thing that he or she is looking for is the lack of smooth pursuit. This is indicated by the involuntary jerking of the eyes as they move from side to side.

The next thing that the officer is looking for is nystagmus at maximum deviation, which occurs when the eye is at the furthest point that it will go on the side.

The last thing that the officer is checking for is the onset of nystagmus prior to 45 degrees. To look for this, the officer will have you start out with your eyes looking forward. You will then slowly follow the stimulus with your eyes. If the officer observes nystagmus before your eyes reach a 45 degree angle, he or she should stop to verify the onset.

While this test is viewed as the most scientific of the field sobriety tests, it is far from perfect. If the test is administered incorrectly, it may case nystagmus, which can be used as evidence to prove that you were intoxicated. If the officer moves the stimulus too quickly, this can affect the results of the test. Another common mistake that officers make is having the driver face the patrol car. The flashing lights from the car may cause involuntary twitching of the eye.

There are also many other things that can cause nystagmus besides alcohol consumption. Some eye conditions, brain tumors, and other neurological conditions lead to nystagmus.

If you have recently failed a Michigan horizontal gaze nystagmus test, there is still hope. An experienced DUI defense attorney will analyze your test results to determine if it was administered inaccurately. Contact The Law Offices of Patrick T. Barone today for help with your case.

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