Call Us Now


The Horizontal Gaze Nystagmus test is usually the first in a series of three field sobriety tests, the others being the Walk-and-Turn and the One-Leg-Stand.

It is said that everyone has nystagmus, which is the unknown involuntary jerking of the eye. There are around 84 causes of nystagmus, caused by disabilities, illness, outside causes and other factors. We have it, but don’t know it. Usually, it is so slight that others don’t notice it, either. Usually, it is lateral (side to side), but can be vertical. Alcohol and drugs will make it more pronounced.

Below, we discuss the test, and how a Tyler TX DWI attorney can help you challenge the test’s results. To learn more, contact Swate Attorney at Law today.


Nystagmus is a condition affecting the eye muscles. The eyes make repetitive, uncontrolled movements. The condition impairs an individual’s ability to interpret depth, reduce visual acuity, and can sometimes affect balance and coordination.

The eye movements can be side to side or up and down. Sometimes they occur in a circular pattern. In order to correct the problems arising from the condition, those who have nystagmus might move their head in ways that many would conceive of as odd. Nystagmus is generally a symptom of some underlying problem. It can be made worse by fatigue and stress. When it occurs in adults, it is usually the result of a problem in the central nervous system (CNS), a metabolic disorder, or impairment due to drugs or alcohol.

Most forms of nystagmus are congenital and only affect those who are very young (under six years of age). Acquired nystagmus, however, is present in adults. It can be the result of an underlying neurological condition or other problems such as:

Among the causes of nystagmus is drug or alcohol induced inebriation. But intoxication is one of many causes that the condition can indicate. Unfortunately, this test is used to railroad a number of unwitting drivers into the court system.


The SFST procedure to detect it is to wave an object in front of the eyes in a certain manner. There is a proper way to do this:

An important thing to understand…this is an eye test created by NHTSA on their own. Optometrists and Ophthalmologists do not use this “test” in their checking and diagnosis of your eyes! It is only for the officers to use in their subjective “tests”. In 26+ years of DWI Defense I have never seen a case where an officer has said the citizen “passed the test”. In fact, every time the officer has said the citizen had the maximum points for failure. After all, at trial the jury has to take his word for the absolute truth because the in-car video cannot see the eyes. For this reason I discount this test to the jury and have found, through experience, acceptable reasons for the jury to not believe this test.


If the only piece of evidence being used against you in a DWI trial is the horizontal gaze nystagmus (HGN), that’s a very winnable case. Here’s why. While the HGN test may be an indication of inebriation, it is also an indication of a number of other disorders. The burden of proof still rests on the prosecution to prove beyond a reasonable doubt that you were, in fact, inebriated when you were pulled over. The police can conduct breathalyzers (which are also not scientific) or blood tests (which must be done properly in order to be scientific). They can’t, on the strength of an HGN test, decide that you are drunk because they waived a magic wand in front of your face.

Common defense to HGN tests include:


As stated above, any number of conditions can cause nystagmus including inner ear infections which are rather common. You can claim that an inner ear infection was responsible for the false positive. If you have documentation to back up that claim, the court will dismiss the case.


Officers receive training give these tests in a specific way. Unfortunately, the environment that they are trained to give the tests in is ideal. If there is a bright light behind the officer giving the test, it could impact the results. Additionally, if the officer holds the stimulus too close to your eyes, that will also throw off the results. Additionally, the stimulus must be moved at the correct speed for the test to be accurate.

According to the Texas rules of admissibility, the test can be admitted into evidence regardless of whether or not the officer has the scientific qualifications to perform the test. The officer is expected to have taken specific courses on field sobriety tests. It’s important to understand that, scientifically, there is no validity to a horizontal gaze nystagmus test whatsoever.

Ophthalmologists do not use the test for diagnostic purposes as nystagmus is easy enough to spot without resorting to other means. If this test is the only piece of evidence presented, a good DWI attorney will be able to get the case tossed or get a verdict in your favor.


In most cases, you will be taken back to the station where you will be administered a blood test. If the blood test comes back negative, that evidence can get buried. You are allowed to ask for an independent blood test to be taken alongside your own. We suggest that you do. The only evidence the police will consider is evidence that can be used to hurt you.

In cases where a breathalyzer was administered, there are ways to defeat that test too. Talk to a DWI attorney early in the process to ensure that your rights are not violated and that you have all the evidence you need to beat the charges.


The important SFST tests are the Walk-and-Turn and One-Leg-Stand which are covered in two other pages. They are the ones that matter. It is best to do them, if possible.

If you have more questions about this “test”, contact Swate Attorney at Law today.