Being stopped by the police can be enough to set anyone’s heart racing, even those who have done nothing wrong. A traffic stop can become even more stressful when a police officer suspects that an individual has been drinking and driving. A motorist may be asked to submit to field sobriety tests, the results of which could determine whether an individual faces DUI charges. One of these tests used in Louisiana is the horizontal gaze nystagmus test. “Nystagmus” refers to the involuntary jerking of one’s eye, which can be exacerbated when an individual is under the influence of drugs or alcohol.

There are really only two steps to this test. First, the officer will assess the driver’s eyes for his or her resting nystagmus. Then the officer will hold something, such as a pen or a finger, about a foot from the driver’s nose and move it from side to side. The driver will be asked to follow the object with his or her eyes without moving the head.

While the test is being performed, the officer will look for several things. The officer will assess whether the driver can smoothly follow the object being moved, whether the eyes start jerking before they reach a 45-degree angle, and whether the eyes involuntarily jerk within seconds of looking as far as they can to the side. If the officer sees four indications of intoxication, keeping in mind that each of the above factors can be counted twice (once for each eye), then he or she will generally have probable cause to make a drunk driving arrest.

Although failing a horizontal gaze nystagmus test may seem damning, it is not the end of the world. In fact, studies have shown that the test is only about 77 percent accurate. Certain medical conditions may cause a person to fail the test. Since this field sobriety test and others are far from perfect, those accused of drunk driving should consider how best to challenge the charges in hopes of avoiding harsh penalties.

Source:, “Horizontal Gaze Nystagmus,” accessed on Nov. 20, 2016