Utah Horizontal Gaze Nystagmus
When an officer suspects an individual of driving under the influence (DUI), he or she may initiate an investigation during the traffic stop to collect evidence that a crime is being committed. In addition to looking for signs of intoxication (such as slurred speech or empty bottles of alcohol in the vehicle), the officer may also administer a series of field sobriety tests to determine if there is probable cause to make a drunk-driving arrest. The horizontal gaze nystagmus is the most common test that is used by Utah law enforcement for this purpose.
Horizontal Gaze Nystagmus
Simply put, nystagmus is an involuntary jerking of the eye. Because this becomes more pronounced when you are impaired by alcohol and/or some drugs, the National Highway Traffic Safety Administration (NHTSA) designed the horizontal gaze nystagmus test to measure the quick jerking of the eye in order to determine if a driver is indeed intoxicated.
To administer the horizontal gaze nystagmus test, an officer will ask the individual to watch a small object (such as a pen or flashlight) while he or she moves it horizontally from side to side. During the test, the individual must keep his or her head still at all times and only follow the object with his or her eyes. While the individual is performing the test, the officer will look for three clues in each eye (six clues total) to determine if an arrest can be made.
The three clues that comprise the horizontal gaze nystagmus test include: an inability to smoothly follow the object from side to side, nystagmus when the eyes are looking as far to the side as possible (also referred to as "maximum deviation"), and the onset of jerking before the eye reaches a 45-degree angle.
Potential Horizontal Gaze Nystagmus Defenses
Although many consider the horizontal gaze nystagmus to be the most scientific of the standardized field sobriety tests, it is certainly not without its problems. For example, there are a number of medical conditions and diseases besides intoxication or drug use that could result in nystagmus. If you have one of these conditions, the results of this test can be challenged.
In addition, the test is only valid if it is administered correctly. If the police officer conducting the test held the object too close to your eyes or administered the test under less-than-ideal circumstances, it could have an impact on your score.