Horizontal Gaze Nystagmus (HGN) test is one of three standardized field sobriety tests (SFSTs) validated by the National Highway Traffic Safety Administration (NHTSA). It is also a test that police in Loveland frequently administer during traffic stops when intoxicated driving is suspected. Though the NHTSA recognizes the HGN as a test that can indicate impairment, this test is not fool-proof. In fact, it has disadvantages, making admitting it as evidence problematic.

Loveland DUI/DWAI defense lawyer, Sean P. Harrell, will thoroughly investigate your case, including the types of tests and manner in which field sobriety tests like the HGN test were administered. At The Harrell Law Firm, we use our skills and resources to ensure you receive the best representation possible. Contact us at 970-236-6576 to learn more about how Sean P. Harrell can help you fight your DUI/DWAI charge in Loveland, Colorado.

What is a Horizontal Gaze Nystagmus Test in Colorado?

The Horizontal Gaze Nystagmus test is one of the common types of standardized field sobriety tests used by Loveland law enforcement officers to help determine whether a driver is under the influence of alcohol.

How is the HGN Test Performed?

The officer conducting the HGN test generally instructs the driver to look at a stimulus, such as a pen or other object, and follow it with both eyes as the officer moves the stimulus to the right and to the left. The officer will analyze the driver's eyes while moving the object from side to side.

Law enforcement officers use the HGN test to measure the involuntary jerking of the eye or nystagmus. Specifically, a driver with a high blood alcohol concentration often exhibits involuntary jerking of an eye as it gazes toward the side while following the stimulus.

Three Major Clues of Intoxication

Law enforcement officers commonly look for three major clues while administering the HGN test. The major clues are examined in both eyes and given a point for the existence of any clue in either eye.

The first clue involves nystagmus in either eye before 45 degrees. The second clue involves nystagmus in either eye when the eye is moved as far as possible to the right or left, such that there is a sustained and distinct jerking. The final clue occurs when the driver is unable to follow the moving object due to nystagmus, this is called lack of smooth pursuit. 

Problems with the HGN Test in Loveland

The problems with the HGN test relate to both the reliability of the test and the administration of the test by law enforcement officers. For instance, the degree of impairment under the HGN test is typically determined by the angle at the beginning of the nystagmus, which often requires an officer to estimate a crucial aspect of the test.

Some of the common problems relating to the administration of the HGN test include the positioning of the stimulus and the officer, lights flashing around the stimulus while the test is conducted, and the lack of a steady hand while moving the stimulus.

Additionally, nystagmus could result from non-alcohol-related causes, such as health issues or medications. Some of the common non-alcohol-related causes of nystagmus include:

  • Ear disorders, such as inner ear fluid movement
  • Eye disorders, such as glaucoma
  • Head injury and brain damage
  • Illnesses, such as influenza, measles, and vertigo
  • Barbiturates
  • Excessive amounts of caffeine
  • Antihistamines

In total, there can be over 38 non-alcohol-related causes for nystagmus that could cause a law enforcement officer to assume a driver is intoxicated.

How a DUI/DWAI Attorney Can Help You in Colorado

A DUI/DWAI charge or conviction often causes many issues in a person's life for several years. If a DUI/DWAI charge is based on a law enforcement officer's utilization of the HGN test, you might have many legal defenses.

The HGN test includes many weaknesses that could help show reasonable doubt in the prosecution's case against a driver. An experienced Loveland attorney could help expose the many issues in the HGN test and the administration of the test.

It is important to understand that failing the HGN test does not automatically mean you are guilty of a drunk driving offense. If you've been charged with DUI/DWAI, your first step should be to call The Harrell Law Firm at 970-236-6576 or complete the Contact form for a free initial consultation about your case.