What Is The Horizontal Gaze Nystagmus Test?
The Horizontal Gaze Nystagmus test (HGN) is a common field sobriety test used by law enforcement officers to detect alcohol or drug impairment in drivers. Nystagmus refers to the involuntary jerking movement of the eyes, which can occur when a person is under the influence of alcohol or certain drugs.
During the HGN test, the officer will ask the driver to follow a moving object, such as a pen or a finger, with their eyes while keeping their head still. The officer will move the object back and forth across the driver’s field of vision to observe any nystagmus that occurs.
There are three different types of nystagmus that officers are trained to look for during the test:
- Lack of Smooth Pursuit: This refers to the inability of the eyes to smoothly track a moving object.
- Distinct and Sustained Nystagmus at Maximum Deviation: This refers to the jerking of the eyes when the object is moved as far to the side as possible and held there for a few seconds.
- Onset of Nystagmus Prior to 45 Degrees: This refers to the jerking of the eyes before they reach a 45-degree angle when the object is moved to the side.
The officer will typically perform the test on both eyes, and look for all three types of nystagmus. If the driver exhibits any of these signs, it could be an indication of impairment.
It’s important to note that while the HGN test can be a useful tool in detecting impairment, it is not foolproof and can be affected by factors such as fatigue, certain medical conditions, and even weather conditions. It is also possible for a driver to exhibit nystagmus without being under the influence of alcohol or drugs.
If you are facing charges for driving under the influence, it’s important to speak with an experienced criminal defense attorney who can help you understand your rights and options.
Is the horizontal gaze nystagmus test 100% accurate?
No, the horizontal gaze nystagmus (HGN) test is not 100% accurate. While the HGN test is one of the most reliable field sobriety tests for detecting alcohol or drug impairment, it is not foolproof and can be affected by various factors.
For example, certain medical conditions, such as inner ear problems, can cause nystagmus, as can certain medications or drugs that are not impairing. Fatigue, bright lights, and other environmental factors can also affect the accuracy of the test.
Furthermore, the HGN test is only one of several field sobriety tests that law enforcement officers use to determine impairment. Other tests, such as the walk-and-turn test and the one-leg stand test, are also used and can provide additional evidence of impairment.
If you are facing charges for driving under the influence, it’s important to speak with an experienced criminal defense attorney who can evaluate the evidence against you and determine whether the HGN test was administered properly and accurately.
Posted 31st May 2023 by DeVore Law Office