Common DWI Field Sobriety Test – Horizontal Gaze Nystagmus

The horizontal gaze nystagmus (HGN) test is 1 of the most common 8 DWI field sobriety tests administered by law enforcement officers when they suspect someone has been driving while intoxicated. When giving the HGN test, the officer observes a suspect’s eyes as they follow a slowly-moving object called a stimulus, which is usually a pen or small flashlight. The officer moves the stimulus horizontally across the suspect’s field of vision. Meanwhile, the officer looks for 3 indicators of impairment in each eye:  (1) if the eye cannot follow a moving object smoothly; (2) if jerking is distinct when the eye is at maximum deviation; and  (3) if the angle of onset of jerking is within 45 degrees of center.

It is believed that when four or more clues appear between two eyes, the suspect likely has a blood alcohol concentration (BAC) of 0.10 or greater. To administer a valid HGN test, the police officer must:

(1.) check for and remove eyeglasses;

(2.) offer standard verbal instructions;

(3.) properly position the stimulus;

(4.) check for equal pupil size and resting nystagmus;

(5.) check for tracking ability;

(6.) check for lack of smooth pursuit;

(7.) check for distinct and sustained nystagmus;

(8.) check for onset of nystagmus prior to 45 degrees;

(9.)  total all clues; and

(10.) check for vertical nystagmus.

HGN tests usually offer experienced DWI defense lawyers an opportunity to challenge the results of the tests, due to the strict guidelines creating room for error by the officer administering it. For example, if the officer neglects to tell the suspect to keep the head still and then fails the suspect for moving her head, it will invalidate the HGN test results. Also, if the officer misplaces the stimulus, the HGN test results are not valid.

DWIs can have other serious consequences, so if you’ve been arrested for operating a vehicle while intoxicated, contact a skilled Baton Rouge DWI lawyer at the Russell Law Firm. The Russell Law Firm represents clients in DWI cases throughout the State of Louisiana, including the parishes of East Baton Rouge Parish, West Baton Rouge Parish, Plaquemines Parish, Livingston Parish, Ascension Parish, Jefferson Parish, Orleans Parish, St. Charles Parish, Terrebonne Parish, Assumption Parish, Lafayette Parish, Lafourche Parish, Lafayette Parish, St. Landry Parish, Evangeline Parish; and the cities of Baton Rouge, Livingston, Denham Springs, Walker, Gonzales, Donaldsonville, Port Allen, Brusly, Addis, Lafayette, Napoleonville, Kenner, Harvey, Marrero, Estelle, Gretna, Metairie, New Orleans, Terrytown, Westwego, Ville Platte, Eunice, Opelousas, Thibodaux, Houma, Belle Chasse, and Hahnville.

DWI Lawyers at the Russell Law Firm, LLC are skilled, experienced, and knowledgeable about the Louisiana DWI laws, related non-DWI statutes, and how to evaluate evidence that law enforcement and prosecutors might try to use against you. If you or someone you know is facing a potential DWI conviction, contact a DWI attorney at the Russell Law Firm at 225-307-0088. We offer free, no obligation initial consultations.

Information furnished herein is only general and not a substitute for personalized legal advice.

****The photograph above is not a depiction of any actual event or scene, but merely a dramatization.

By: Danny D. Russell, Esq.