How to Challenge a Horizontal Nystagmus DUI Sobriety Test

 May 26, 2026 in Elite Lawyer

If you are arrested for DUI, one of the things police may use against you is a field sobriety test called the Horizontal Gaze Nystagmus test, or HGN test. Most of us have seen this "test," even if we’ve never taken it: An officer shines a flashlight or holds a pen in front of your face and asks you to follow it with your eyes. A few minutes later, the officer uses it to claim your eye movements show signs of intoxication.

In 2026, HGN testing remains one of the most controversial parts of DUI investigations across the United States. Police officers and prosecutors often present the test as scientific and reliable, but there are many reasons an HGN test can give inaccurate or misleading results.

If you are facing DUI charges after failing an HGN test, a local DUI defense attorney from Elite Lawyer’s directory can give you the outstanding representation you need to fight the charges. 

What Is a Horizontal Gaze Nystagmus Test?

"Nystagmus" refers to involuntary jerking or bouncing movements of the eyes. During an HGN test, an officer looks for specific eye movements while the test subject follows an object moving side to side. The theory behind the test is that alcohol and certain drugs exaggerate these involuntary eye movements.

Police officers are trained to look for clues such as:

• Jerking in the eyes at certain angles

• Difficulty in smoothly following the object

• Eye movement before the eyes reach a certain point

Officers typically use the HGN test alongside other field sobriety tests like walking in a straight line, standing on one leg, or counting backwards. However, the HGN test is far more technical than these other roadside exercises. It requires specific training and must be done correctly to have any real reliability.

Controversy Over the HGN Test 

Police and prosecutors often treat HGN testing as highly scientific evidence, but there are major limitations. Accurate results depend on police officers using the right timing, moving their light or finger correctly, accurately noting the eye movements, and not confusing results with other environmental or medical factors. Even small mistakes can affect the results.

Many innocent factors besides alcohol can also cause nystagmus or abnormal eye movement, including:

• Fatigue

• Anxiety

• Certain medications

• Neurological conditions

• Inner ear disorders

• Concussions or head injuries

• Flashing lights

• Natural eye conditions

This becomes especially important during nighttime traffic stops, where flashing patrol lights, passing traffic, stress, and exhaustion may all affect a driver’s performance.

Can an HGN Test Be Wrong?

HGN testing is not foolproof, and false positives happen for many reasons. For example, imagine a driver who has been awake for 20 hours after traveling for work. The driver is tired, nervous, standing on the side of a busy highway at night, and dealing with bright flashing emergency lights. Those conditions alone can affect eye movement and concentration.

In other cases, officers simply perform the test incorrectly. The National Highway Traffic Safety Administration (NHTSA) has established guidelines for field sobriety testing, including how HGN tests should be done. If officers don’t follow the correct procedures, the reliability of the test is seriously weakened.

Is the HGN Test Enough to Convict Someone of DUI?

Most DUI prosecutions rely on multiple pieces of evidence together. In addition to the results of the HGN test, a police officer will look at your driving behavior, what you say, and other field sobriety tests. If the officer thinks there is probable cause, they can arrest you and take breath or field sobriety tests. 

However, HGN evidence can still strongly influence prosecutors, judges, and juries. This is why you need to have an attorney who knows how to challenge weak or improperly administered tests. In some cases, undermining the field sobriety testing may significantly weaken the prosecution’s overall case.

Contact Elite Lawyer for Help Finding a DUI Defense Attorney

If you were arrested after failing a Horizontal Gaze Nystagmus test, the evidence might be a lot weaker than you think. DUI cases involve a police officer’s subjective judgment and questionable testing procedures.

Elite Lawyer recognizes attorneys across the United States who demonstrate professionalism and dedication in criminal defense and DUI representation. Contact Elite Lawyer at 833-403-5483 to learn more or to find a qualified local DUI defense attorney near you.