Medical professionals use the term nystagmus to refer to rapid, uncontrollable movements of the eye. These movements can cause the eye to move circularly, side to side, or up and down. HGN (horizontal gaze nystagmus), specifically, is the involuntary jerking of the eye when a person gazes to the side.
Police officers may use an HGN test as part of an arrest for driving under the influence (DUI). You can learn more about this test, how it can impact a DUI case, and your options for a defense by reaching out to an Ellijay DUI lawyer for help and legal support.
What’s Nystagmus and What Does HGN Mean?
Nystagmus is an involuntary jerking of the eye. Nystagmus can have many causes – flashing lights, rotation, head injury, the position of the head, central nervous system depressants (like alcohol), and some people even have a natural nystagmus (called a resting nystagmus).
HGN refers to horizontal gaze nystagmus, a specific type of involuntary movement. Law enforcement officers often use a horizontal gaze nystagmus test as part of standardized field sobriety tests during DUI stops in Georgia.
How Alcohol Affects Nystagmus
The consumption of alcohol and some other substances (primarily depressants) can increase the eye movements associated with nystagmus. These movements are involuntary and do not impact a person’s vision, so drivers may not notice the onset of nystagmus.
Due to the effects of alcohol impairment on nystagmus, police officers include HGN assessments in field sobriety testing. A lawyer can tell you more about what nystagmus is and what HGN means.
How Do Police Officers Complete HGN Testing?
Officers often complete HGN assessments as part of standardized field sobriety tests. Before a test, they will look for an area away from flashing lights, so as not to skew the results. They should ask drivers about their usage of contact lenses and about medical conditions that could impact test results.
Officers will request a driver to follow an object, typically a light, looking for:
- Evidence of smooth pursuit or jerkiness of the eye
- Nystagmus at maximum deviation
- The place at which the onset of nystagmus occurs
In addition to completing an HGN test, police officers may request that drivers complete other field sobriety tests, like the walk-and-turn test or the one-leg stand. They may also request that a driver submit to breath testing to measure their blood alcohol concentration (BAC).
Is HGN Testing Accurate?
The HGN is by no means perfect and can give a false positive for alcohol impairment for a driver who wasn’t drinking. Several factors besides alcohol usage can cause nystagmus, including:
- Medical conditions
- Fluid in the inner ear
- Neural activity
- Eye strain
“Failing” nystagmus testing does not prove that your blood alcohol level exceeds the limits established by the legal system in Georgia and does not mean you should automatically face a conviction for drunk driving.
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Do You Have to Submit to HGN and Other Field Sobriety Tests?
Most drivers can legally refuse field sobriety testing in Georgia. These tests are often nerve-wracking and may provide evidence that the police could use during a DUI investigation, so some drivers choose to refuse to participate.
Generally, drivers can refuse the walk-and-turn test, the one-leg stand, the HGN test, and even roadside blood alcohol content tests. However, drivers cannot legally refuse to submit to blood alcohol level testing after an arrest.
Additionally, refusing field sobriety testing does not mean the police will not complete an arrest. Law enforcement officers can still arrest a driver who refuses all of these tests if they believe they have probable cause.
What Happens if You Refuse a BAC Test After an Arrest?
If you refuse to comply with BAC testing after the police arrest you for a DUI, it can result in harsh legal penalties. You could face a license suspension and other consequences for this action.
If you feel unsure about your legal rights and what you have to do when dealing with DUI allegations, you should reach out to an attorney for help immediately.
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Lawyers Can Help After a DUI Arrest
If the police accuse you of drunk driving, you may have a chance to build a defense, even if you “fail” a HGN test. An attorney can review the facts about your arrest and get to work on your legal needs right away.
Depending on your circumstances, an attorney may focus on getting the court to drop your charges. Your attorney could also take steps to get your charges reduced through a plea bargain or fight for you in court.
Talk to Us to Learn More About Nystagmus and HGN Tests
So, what is nystagmus, and what does HGN mean? Nystagmus is an involuntary movement of the eyes. Nystagmus can impact the way eyes move horizontally, vertically, or even circularly.
Alcohol can impact HGN (horizontal gaze nystagmus), so police officers sometimes use a horizontal gaze nystagmus test when carrying out a DUI arrest. These tests do not directly influence DUI convictions.
If you have been charged with DUI and submitted to an HGN test, call one of Teague Law’s experienced DUI attorneys who knows the science behind the HGN test and its flaws to defend your rights now. Our team has extensive experience, and we’re ready to help with your defense.
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