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The Horizontal Gaze Nystagmus (HGN) test is one of three standardized field sobriety tests (SFST's) validated by the National Highway Traffic Safety Administration (NHTSA).  It is also a test that police in Los Angeles administer frequently 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 its disadvantages, which make admitting it as evidence problematic.

In California, our DUI defense lawyer will thoroughly investigate your case, including the types of and manner in which field sobriety tests like the HGN test were administered.  At Berglund Law Office, P.C., we use our skills and resources to ensure you receive the best representation possible.  Call our office at (877) 667-1205 or submit the CONTACT form to learn more about how our DUI defense attorney can help you fight DUI charges in Los Angeles.

What is a Horizontal Gaze Nystagmus Test in California?

The Horizontal Gaze Nystagmus (HGN) test is one of the common types of standardized field sobriety tests used by Los Angeles law enforcement officers to help determine whether a driver is under the influence of alcohol.  It is often the first field sobriety test administered. 

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 (total of six clues). 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 the nystagmus. 

Problems with the HGN Test in Los Angeles

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. 

There are many innocent reasons why a person does not perform the HGN perfectly.  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

There are many non-alcohol-related causes for nystagmus that could cause a law enforcement officer to mistakenly assume a driver is intoxicated.

How a DUI Attorney Can Help You in California

The HGN test includes many weaknesses that could help show reasonable doubt in the prosecution's case against a driver.  An experienced Los Angeles DUI 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, your first step should be to call Berglund Law Office, P.C. at (877) 667-1205 or submit our CONTACT form for a free consultation about your case.


Our office specializes in representing individuals facing traffic violations. We represent our clients in both court and at DMV hearings. Your case will be handled with the personalized attention and expertise that it deserves.

Free Consultation

There is no charge for the phone consultation. Our office specializes in representing individuals facing traffic violations. Attorney Robert D. Berglund will personally speak with you about your case and provide you with an honest analysis. Contact us today.