HGN Test

Franklin DUI Defense Lawyers Who Tell You the Truth about the Horizontal Gaze Nystagmus Test, Tennessee

Learn more about how field sobriety tests work

Field sobriety tests are conducted by law enforcement officers (at the local and state level) who, in the course of a DUI stop, believe that the driver has been impaired by alcohol or drugs. They are done exclusively for the benefit of building a case against an alleged drunk driver. Of the three standardized FSTs, the Horizontal Gaze Nystagmus test (HGN) is often touted as the most accurate of the exams, relying on an officer’s ability to identify involuntary responses of the eye.

While it may seem like nothing can defend against the HGN, at the Law Offices of Adrian H. Altshuler & Associates, we know better. Our experienced DUI defense attorneys in Franklin, Brentwood and Columbia have successfully defended people who stand accused of DUI based on the results of this test; we know its weaknesses and its flaws. We know when the test is admissible under the law and when it can be thrown out.

How does the horizontal gaze nystagmus test work?

When an officer conducts the HGN test, he or she is looking for involuntary motions made by your eye. Under normal circumstances, a person’s eye will “jerk” around a bit when you look up and to the side; that jerking motion is called nystagmus. However, in a person who has imbibed alcohol (or taken another kind of depressant), the “nystagmus is exaggerated and may occur at lesser angles,” as per AAA.

How is the horizontal gaze nystagmus test performed?

After you are pulled over and asked to step out of the car, the officer will hold up an object – usually a pen or penlight, or maybe his or her finger – about 12-15 inches away from your face. Starting in the center, he or she will then move the object slowly towards your left ear. If the officer detects nystagmus, he or she will repeat the test moving towards your right ear. To object of this first part is to test how smoothly your eye “tracks” the object in front of it.

Next, the officer will (starting again from the center) move the object towards your left ear, and hold it there for at least 4 seconds. He or she will repeat this same motion for the right eye as well. This portion of the test is designed to see if the nystagmus is sustained.

Finally, the officer (starting again in the center) will move the object more quickly to your left shoulder, and then again to your right. This allows him or her to view the exact point at which nystagmus is apparent.

Each of these three clues is worth two points: one for each eye. If the officer feels you exhibit four of the six clues, he or she can may claim you are driving above the legal limit.

Defending against HGN results in a courtroom

Because you cannot control the involuntary movements of your eye, the HGN test is often considered the “gold standard” for field sobriety tests in Tennessee. However, there are a number of factors that could contribute to an incorrect assessment of drugged or drunk driving:

  • Nystagmus is affected by the inner ear. A person who has had nothing to drink can also fail the HGN because of prior health concerns, such as permanent damage or scarring. If you have an ear infection or a condition that affects your brain, this may also cause a “False positive” HGN result.
  • All tests must be given in the exact same way to be accurate. When officers are trained to give these tests, they are given that training in a controlled environment. If the officer holds the object too close to your face, or points you in the direction of a flashing light, it is possible that outside visual distractions can affect your eye’s response.
  • Law enforcement officers are human, which means they make mistakes. Because there is no way to prove that the officer held the object exactly the right distance from your face, or moved it in the exactly the correct manner (or at the correct speed) mandated, the argument could be made that he or she deviated from standard operating procedure, and that the test results should be dismissed. If the officer fails to inform you that you need to keep your head still, or that you shouldn’t move your eyes until you are instructed to do so, the test may also be deemed inadmissible.
  • HGN is scientific, which means an expert must testify. The average person can understand what the Walk and Turn test or the One Leg Stand test are, without any additional information. However, the average person does not know what nystagmus is, and under Tennessee Rule of Evidence 702, “If scientific, technical, or other specialized knowledge will substantially assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or education may testify in the form of an opinion or otherwise.” Most law enforcement officials are not experts, and therefore the HGN can be deemed inadmissible before it evens gets to court.

The HGN is often combined with the Walk and Turn test and the One Leg Stand test to build a complete picture. Without the HGN results, however, it can be difficult for an officer to prove that your balance test scores paint an accurate picture.

What should I do if I am arrested for DUI after “failing” the HGN?

Remember this above all: if you are asked to submit to a field sobriety test like the HGN, you have the right to refuse. You do not have to submit to field sobriety tests – period. But if you are charged with drunk driving after the HGN test, you need a skilled Franklin DUJI defense attorney to represent your best interests. Our experienced team can build a defense strategy that is customized to you. We review the police report, speak with witnesses, and will work with our own outside field experts if that is what it takes to protect your freedom and your rights.

Learn more about your rights and field sobriety tests in Tennessee

The Law Offices of Adrian H. Altshuler & Associates has been fighting for the rights of the accused for 30 years. Even if you “failed” the horizontal gaze nystagmus test, that does not mean you automatically have to lose your license. To schedule a consultation with one of our DUI defense lawyers in Franklin, Brentwood or Columbia, please call 615-977-9370, or fill out our contact form. We also handle DUI cases in the surrounding areas of Spring Hill, Murfreesboro, Lawrenceburg and Pulaski, Tennessee.