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Published on 1/26/2022, 9:26:00 PM

What is the "HGN" Test? Everything you need to know for your DUI case.

When a law enforcement officer suspects a driver in Maryland of driving under the influence (DUI) of alcohol or drugs, the officer may administer one or more tests to the driver to determine his or her level of impairment.

The three most common tests administered by police officers to check for intoxication are the horizontal gaze nystagmus test (HGN), the one-leg stand test (OLS), and the walk and turn (W&T) test. The results of these tests can determine whether an officer decides to place a suspect under arrest for impaired driving.

A DUI charge in Maryland can have severe consequences, including incarceration, fines, and the loss of one's license. Therefore, if you've been arrested for DUI in Maryland, you should contact an experienced Maryland DUI defense attorney as soon as possible for assistance.

In this week's DUI topic of the week, we examine the HGN test in Maryland.

Officer administering the HGN test

The Science Behind the HGN Test

The HGN test is designed to detect driver impairment. It does so by observing a driver's eyes. The term "nystagmus" refers to the jerking or bouncing of the eye.

"Horizontal gaze nystagmus" refers to the involuntary jerking of a person's eye when it gazes to the side. When administering the HGN test, police officers observe drivers for horizontal gaze nystagmus, which is an involuntary motion that becomes more pronounced when an individual is impaired by alcohol or certain drugs.

This occurs because alcohol depresses the nervous system, resulting in a noticeable effect on a person's ability to perform sideways eye movements in a smooth manner. In fact, drivers who exhibit these exaggerated eye movements aren't even aware of it because HGN doesn't usually affect the vision. Additionally, the test is designed for you not to know that this indicator is what the officer is looking for, because they do not ever mention the word Nystagmus when giving the instructions.

Multiple studies have concluded that the HGN test is an accurate indicator of alcohol impairment. However, these tests aren't perfect, and criminal defense attorneys routinely successfully challenge their results in court. In Maryland, an Officer who is attempting to testify about the HGN test must be qualified as an expert, and is subject to a challenge on their expertise.

How Police Officers Conduct the HGN Test

When a police officer pulls over a driver on suspicion of driving under the influence of alcohol or drugs, he or she may request that the driver perform an HGN test.

Before administering the test, the officer usually asks the driver whether he or she wears contact lenses or has any medical issues that would affect the results. The officer must also ensure that he or she administers the test either in a well-lit area or with the use of a flashlight to ensure that he or she can clearly observe the eyes of the driver.

However, the suspect must face away from the police cruiser's flashing lights and the lights of passing cars during the administration of the test, as these factors can skew the results. If a Police Officer fails to control these outside factors, the results of the test could be invalid.

After ensuring that these environmental conditions are correct, the officer should then asks the suspect to follow an object (usually a pen light or the tip of a pen) with only his or her eyes. The officer places this object 12 to 15 inches away from the suspect's face.

HGN Signs of Intoxication

When administering an HGN test, the officer observes the suspect's eyes for the following signs of intoxication:

  • Lack of smooth pursuit: Under normal circumstances, the eyes are able to follow objects smoothly. The eye movements of an intoxicated person, however, are jerky.

  • Distinct nystagmus at maximum deviation: Another sign of intoxication is a distinct jerking motion of the eye after being held toward the outer edge for four seconds.

  • Onset of nystagmus prior to 45 degrees: Finally, if the eye jerks before the object is 45 degrees from the center of the suspect's face as the officer moves it towards the outside of the suspect's shoulder, then this is considered a sign of intoxication.

Challenging HGN Test Results

Although the HGN test is considered to be reliable, it isn't perfect, and this provides criminal defense lawyers with opportunities to challenge HGN test results in court. There are many ways to challenge the results of an HGN test. For example, if an HGN test is not administered properly, this can cause a driver to fail the test even though he or she is not actually impaired.

Therefore, if a police officer who administers a test fails to follow specific procedures when doing so, an attorney can challenge the results of the test in a court of law.

Additional issues that can cause a driver to show signs of nystagmus include:

  • Certain medical conditions
  • Certain types of medication
  • Head injuries
  • Vision disorders

If a driver's attorney can provide evidence, such as documentation or medical records, that demonstrates the driver has a condition that affected his or her performance of the HGN test, this can greatly improve the driver's chances of winning his or her DUI case.

DUI Consequences in Maryland

If you've been charged with DUI in Maryland, you should take it very seriously. A DUI/DWI conviction can result in a jail sentence, hefty fines, and the loss your driving privileges. In addition, having a DUI conviction on your record can make it difficult for you to find employment, go to school, obtain certain loans, or even secure suitable housing.

Given the potential consequences of a DUI conviction in Maryland, you should do everything in your power to fight the charge-and the best way to do so is to hire an experienced criminal defense attorney. An attorney may be able to help you secure a probation before judgment, keeping the conviction off your record.

Contact a Maryland DUI Attorney

If you are facing a DUI charge in Maryland, you need an experienced Maryland DUI attorney on your side. Whether it is your first offense, or your [second or third DUI]](https://frizwoods.com/subsequent-offender-dui), we can help.

At FrizWoods, we are passionate about providing our valued clients with aggressive legal representation in Maryland DUI cases. Attorneys Max Frizalone and Luke Woods understand how a DUI conviction can affect a person's life, and they have years of experience successfully fighting DUI charges.

Therefore, when you come to FrizWoods for help, we will do everything in our power to ensure that your case has a satisfactory result. Please contact us as soon as possible to schedule a free initial consultation with one of our talented DUI defense attorneys.