What Happens During a DUI Traffic Stop? (Part II)

In our recent DUI blog post, "What Happens During a DUI Traffic Stop? (Part I)," we discussed the typical DUI traffic stop, the likely conversation between you and the officer, and the three Field Sobriety Tests the officer would most likely ask you to perform: the Horizontal Gaze Nystagmus Test (HGN), the Walk and Turn Test, and the One-Leg Stand Test.  In this installment we'll discuss what the HGN test is, what is expected of a DUI suspect in performing the test, and how a DUI lawyer can help you exclude the results or significantly minimize their value as evidence in your DUI case.

During the HGN test, the officer will hold a stimulus, such as a pen, 12-15 inches from the suspect's face with the tip slightly above the eyes. He then will move the stimulus smoothly from side to side, from the center of the field of vision towards each ear while the DUI suspect keeps his or her head still. The "clues" of alcohol intoxication the officer is looking for are a lack of smooth pursuit by the eyes, distinct nystagmus at maximum deviation (the farthest point from center), and onset of nystagmus prior to 45 degrees. Nystagmus is described as a "bouncing" eye motion that, in this case, is displayed jerking motion, where the eye moves slowly away from a fixation point and then is rapidly corrected through a fast movement.   Most types of nystagmus, including HGN, are involuntary motions, meaning the person exhibiting the nystagmus cannot control it. In fact, the subject exhibiting the nystagmus is unaware that it is happening because the bouncing of the eye does not affect the subject's vision. 

Eyeglasses and hard and soft contact lenses may effect the accuracy of the HGN test.  An officer may ask you to remove your glasses, but will not likely ask you to remove your contacts.  The officer may choose to shine a light in your eyes to illuminate your face, but he should not face you towards passing cars or blinking lights.  There are also certain medical conditions that can cause nystagmus, such as some diseases of the inner ear.  The test should not be performed on anyone with an obvious abnormal eye disorder.

You should remember that through your entire DUI stop and arrest, including this test, you will be video and audio recorded.  The video, however, will not show your eye movements if the video is taken from inside the police cruiser.  Also, if you have any medical impairments that you believe would hinder your ability to take the HGN test you should make the officer aware of them.

DUI attorney understands the procedures used by officers in administering field sobreity tests.  The HGN test's accuracy is seriously compromised if the exact procedures are not followed.  A DUI lawyer can examine how the HGN test was performed, find any mistakes, and attack the credibility of any unfavorable results.

In the next part of this DUI traffic stop series we will discuss the Walk and Turn Test, how it is administered, and what officers look for when observing DUI suspects.

South Carolina DUI Attorneys

Anderson & Schuster, Attorneys at Law, LLC is a law firm based in Mount Pleasant, SC that helps people charged with DUI and DUAC in the Charleston, Mt. Pleasant, North Charleston, Summerville, Goose Creek, Hanahan, West Ashley, James Island, Folly Beach, Isle of Palms, Sullivans Island and Moncks Corner areas.