Suspected of Driving While Intoxicated (DWI)- HGN explained

horizontal-gaze-nystagmus HGN

If an officer stops you and believes you have consumed alcohol, the very first test an officer will complete is called the horizontal gaze nystagmus test, aka HGN, aka Here Goes Nothing!

This is one of three of the standardized field sobriety tests developed by NHTSA that has a scientific element. And it is the test the officers trust most. The officers are taught by other officers in the police academy that they can diagnose someone with intoxication if they move a stimulus in front of someone’s eyes at designated speeds and hold the stimulus at specific locations for a specific period of time. This is why the test is commonly referred to as the “Here Goes Nothing” by defense attorneys.

HGN as Science

The horizontal gaze nystagmus test is considered a scientific test in most courts around the Country including Texas. Usually, for a scientific test to be admissible as evidence against you, there must be an expert to give the testimony in court. Texas Courts have found that as a matter of law, the principles behind the HGN test are scientifically reliable.  However, the State must prove that the officer is both certified in the administration of the HGN and that the officer conducted the test in the specific manner designed by NHTSA. 

It’s important that your DWI attorney knows the science behind the HGN and the proper administration of the test. The attorneys at Soyars & Morgan Law are certified in the administration of the HGN and can easily point out an improper administration of this test. 

Because the HGN is considered a scientific test, any departure by an officer from the standardized administration of the test, can be means to ask for this test to be suppressed or thrown out as evidence against you in your trial. The administration of the test must be strictly followed by the officer or the results can be unreliable or invalid.

What are the Police Looking for During Horizontal Gaze Nystagmus (HGN) Test?

Nystagmus is a naturally occurring condition in the eye. Everybody has nystagmus. Nystagmus is the bouncing or jerking of the eye that can be caused by a number of factors. There are 47 different types of nystagmus. There are many different causes of nystagmus yet nystagmus generally appears the same in an individual’s eyes, regardless of the cause. 

Officers are taught to look for one type of nystagmus… Horizontal Gaze Nystagmus. Officers are taught that if they see at least 4 out of 6 clues present in the HGN test that you are more than likely, intoxicated. If officers see HGN in your eyes, you will be placed under arrest for DWI regardless of how you perform on the other standardized field sobriety tests.

How the HGN test should be performed

Generally, before an officer begins the test, he will ask you to remove your glasses. He will ask you if you have contacts, but you are not usually asked to remove your contacts.  The officer should ask you a series of qualifying questions about whether you’ve had head trauma or a concussion. 

Instruction Phase

An officer will ask you to stand with your feet together and hands by your side. You will then be instructed to follow the stimulus the officer will move in front of your eyes with your eyes and your eyes only. You will be asked to not move your head. While, moving your head is not a clue that the officers are looking for, moving your head can affect the officer’s results. 

Qualification Phase

The first set of passes is to check for medical impairments. The officer should move the stimulus in front of your face to check for equal pupil size and equal tracking. If your pupils are not equal or do not track together, you are not a candidate for the HGN and all results obtained are not reliable. The office will move the stimulus faster than during the remainder of the test. Generally, one second from the center to the side of your face. 

Smooth Pursuit Phase

After an officer believes that he observes equal tracking and equal pupil size in your eyes, he will look for lack of smooth pursuit. The officer will move the stimulus from the center of your face to the far left and back to the center and then to the far right of your face and back to center. The stimulus should be moved at a rate that takes at least 2 seconds to get from the center of your face to the outside and 2 seconds back. Officers are taught to look for each clue twice. The Smooth pursuit phase should take at least 16 seconds for the officer to complete.

Maximum Deviation Phase

The officer should move on to check for distinct nystagmus at maximum deviation. Maximum deviation is the point at which the eye has moved to one side and cannot move any more to that side. An Officer defines it as the point at which he can no longer see any white left in the corner of the eye. The officer will then hold the stimulus for at least 4 seconds before moving the stimulus back to the center and checking the right eye.  It is insufficient that an officer moves to maximum deviation and claims that nystagmus is visible without holding the stimulus for a minimum of 4 seconds. By the time the officer is checking your distinct nystagmus at deviation your eyes are tired. I generally have clients complain of the length of the horizontal gaze nystagmus test. This phase alone should take at least 32 seconds as the officer must check each eye for at least 8 seconds for a total for passes. 

Angle of onset prior to 45 degrees phase

The final clue the officer is taught to look for is presence of nystagmus prior to 45 degrees. To check for this clue the officer must move the stimulus very slowly to an estimated 45 degrees on your body. Officer’s use no tools to measure 45 degrees. Rather, they estimate it by using the shoulders of your body. Once the officer believes he observes nystagmus prior to 45 degrees he should pause the stimulus to confirm his belief that he did in fact observe nystagmus. 

Vertical Nystagmus

Officers generally will also check for vertical nystagmus although this clue has not been scientifically validated and should not be allowed in testimony. Officers will generally try to introduce the presence of vertical gaze nystagmus in their testimony as officers are taught that the presence of vertical gaze nystagmus indicates a high level of intoxication due to alcohol or the presence of narcotics in your system. 

Common Mistakes in the Horizontal Gaze Nystagmus

Officers commonly move the stimulus too quickly or do not take enough passes when assessing one for HGN. The validated test must include at least 14 passes and take at least 82 seconds. If the officer moves the stimulus too slowly or holds the stimulus too long during one of the passes. Officers can also mistakenly curve the stimulus upwards or downwards as they move the stimulus across your face, called looping.  If any of these mistakes are present the test is not reliable.

What You Should Do If You Fail the Horizontal Gaze Nystagmus

If an officer stops you or comes into contact with you while you are driving or operating a car and believes you have consumed alcohol, they will ask you to complete the HGN. The officers put most of their belief in this test. If they move from this test to the divided attention tests, like the walk and turn and one leg stand, they have made up their mind that they are going to arrest you for driving while intoxicated. Although, an officer won’t admit that. Officers claim that they must do a complete and thorough investigation before determining whether they have probable cause to arrest you for DWI. But if you refuse to complete the walk and turn test and the one leg stand test, they will then testify that they have probable cause to place you under arrest for DWI. 

Competent defense attorneys have the scientific knowledge and understanding of the horizontal gaze nystagmus. The attorneys at Soyars & Morgan Law are certified in the administration of the HGN and can review the officer’s camera to ensure it was properly administered. 

Soyars and Morgan Law, P.C. is a San Antonio, Texas law firm focusing on DWI, Criminal Defense, and Family Law. The attorneys at Soyars and Morgan Law, P.C. have experience litigating DWI cases.  If you, or someone you know has been charged with driving while intoxicated in San Antonio, and has questions about challenging a field sobriety test result and needs DWI representation, contact Soyars and Morgan Law, P.C. today! We can help you fight for your freedom and personal reputation.

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