The horizontal gaze nystagmus (HGN) test is one of three standardized field sobriety tests created by the National Highway Traffic Safety Administration (NHTSA). Nystagmus is the technical term for the involuntary jerking of the eye and it occurs when a person is intoxicated. Specifically, a person’s nervous system will display a breakdown in the smooth and accurate control of the eye muscles. This breakdown may result in the inability to hold the eyes steady, which results in an observable change affecting the oculomotor control of the eye. A horizontal gaze nystagmus is a lateral jerking movement when the eye rotates towards the side.

Nystagmus can be caused by several sources, including the consumption of alcohol or drugs. These impair the ability of the brain to properly control the eye muscles and result in a jerking of the eye. The higher a person’s blood alcohol content (BAC) level, the more pronounced the nystagmus. However, even a sober individual’s eyes will occasionally jerk when the eye rotates towards the side. This is known as a “physiological nystagmus.”

The first step in the administration of the HGN test is to check the suspect’s eyes for equal tracking (i.e., can the eyes follow an object together) and equal pupil size. The officer will then position an object, typically a finger or pen, approximately 12-15 inches from the driver’s nose at a slightly raised level. The officer will move the object smoothly to the right, then to the left, and back to the middle. If the suspect’s eyes do not track together, or the pupil have noticeably different sizes, the suspect may be suffering from a medical issue or injury that could compromise the test.

If there is no problem with tracking or pupil size, the officer will repeat the process three times, checking each time for a “clue” of intoxication. The object should take approximately two seconds to be moved from the middle to the far side of the eye. The officer will then move the object back to the middle, taking approximately two seconds.

During the first pass, the officer is determining whether each eye is able to smoothly pursue the object. During the second pass, the officer will be focused on a distinct nystagmus at maximum deviation. This means that the officer will move the object to the side of the suspect’s face and hold it there for approximately four seconds. If the suspect’s eyes continue to jerk after two or three seconds, the officer notes a clue of intoxication.

Finally, the officer will move the object at a speed taking approximately four seconds to reach the edge of the suspect’s shoulder. The officer is determining whether the involuntary jerking begins prior to reaching maximum deviation (45 degrees). If the officer finds at least four clues, there is a significant likelihood that the suspect has a BAC level of 0.08 or greater.

There are issues with relying on the HGN test because there are multiple causes of nystagmus. Syndromes such as influenza, epilepsy, muscular dystrophy, multiple sclerosis and other psychogenic disorders have been shown to product nystagmus. Moreover, conditions such as hypertension, motion sickness, glaucoma, and eye muscle fatigue may result in gaze nystagmus. Finally, caffeine, nicotine and aspirin can also lead to a nystagmus that is very similar to a nystagmus resulting from alcohol.

Under Ohio law, evidence and testimony regarding the results of a field sobriety test may be presented in court if it is shown by clear and convincing evidence that the officer administered the test in substantial compliance with generally accepted field sobriety tests, including those set by the NHTSA. As to HGN tests, the Ohio Supreme Court has held that the results are admissible if proper foundation is laid as to the officer’s training and ability to administer the test and as to the technique used by the officer administering the test. Once the issue is raised by the defense, the state has the burden of demonstrating that the officer substantially complied with the NHTSA standards.

So, what does “substantial compliance” mean? In State v. Burnside, the court stated that “de minimus” or “minor procedural deviations” are not substantial. The State must set forth the testing standards, offer testimony that the testing standards have been accepted and demonstrate that the officer substantially complied with those standards. According to Village of Gates Mills v. Mace, if the State fails to introduce evidence of the standards (i.e., introduce the NHTSA Manual into evidence), the State will not meet this burden.

Another common mistake that prosecutors make in having the officer testify as to the HGN test is not having the officer testify as to what is required under the NHTSA Manual or whether the officer followed the Manual when administering the test. A recent Ohio case, State v. Holzapfel, demonstrates this point.

Columbus and Delaware, Ohio DUI/OVI Defense Attorney

If you have been charged with a DUI/OVI offense in Columbus or Delaware, Ohio, call Johnson Legal, LLC at (614) 987-0192. DUI/OVI defense is a very technical and complicated field of law. Attorney David Johnson is an experienced DUI/OVI attorney who will discuss your case, assist you in preparing a strong defense, and vigorously defend you against the DUI/OVI charge.