When you are pulled over for a DUI or DWI, it often can feel like a confusing time. Understanding the process officers go through will help you navigate the process. Officers will often ask you a to perform a series of tests to determine whether those results will tell if you are intoxicated. In this post, we will discuss what happens in the one of the tests officers conduct, the horizontal gaze nystagmus test, or HGN as it is commonly referred.
Officers are trained by the National Highway Transportation Safety Administration (NHTSA) guidelines, established and monitored by the federal government’s Department of Transportation, to use these tests as a measure to determine whether an individual may be under the influence of drugs or alcohol.
It is important to note these tests are not perfect indicators of intoxication. There may be many different factors which may impact the outcome of these tests. Most importantly, while officers may be trained in administering and making outcome determinations from these tests, it is still subjective to the officer’s decision.
Finally, depending on the circumstances of your case, an officer will not use these results alone to make a determination of intoxication. Instead, an officer will use these test results and what they call the totality of the circumstances, or all of the different factors they observe (including, but not limited to, slurred speech, how you are driving, and difficulty following directions).
Horizontal Gaze Nystagmus Test
Often referred to as HGN, this test is designed to measure the involuntary jerking your eyes. Officers will have you stand straight and look ahead. At this point, an officer move one finger (or a pen) from left to right multiple times while observing your eyes. Once this is complete, the officer will then move his finger up and down while observing your eyes. The entire test is designed to observe any involuntary jerking of the eyes.
In analyzing your pursuit of the finger or pen, officers will also look to see if you have followed the finger or pen with a smooth pursuit. The officer will look for the jerking or bouncing before the eye reaches a 45 degree angle. Studies have proven that the eye will jerk or bounce due to intoxication, so this is an important test for officers to use in determining whether an individual is showing signs of intoxication.
The horizontal gaze nystagmus test is accurate only about 77% of the time. There are many reasons an individual may fail the test that do not involve intoxication.
· An individual may have a natural nystagmus that gives officers a false result
· Infections, illnesses, or prior injuries.
· Medications
· Improper administration of the test
· Bright or flashing lights
Mounting a Legal Defense
With a reliability of 77%, the HGN test is not a full-proof indicator that an individual may be intoxicated. Experienced trial attorneys can use many of the factors listed above, and other reasons, to defend you against the results of these tests. Consult our experienced DUI attorneys today to begin crafting the best legal defense to beat your case. Also see our blog on what to do after a DUI stop for more information.