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The Horizontal Gaze Nystagmus Field Sobriety Test

by Joseph C. Maya on Aug. 11, 2017

Criminal DUI-DWI Criminal 

Summary: A blog post about one of the field tests a police officer may employ during a DUI pullover.

For a free consultation with an experienced criminal defense attorney, please call the offices of Maya Murphy, P.C. today at (203) 221-3100 or Joseph C. Maya, Esq. at

Under Connecticut law, any person who operates a motor vehicle within the State shall be deemed to have given his or her consent to a chemical analysis of the operator’s blood, breath or urine and, if such person is a minor, such person’s parent, parents, or guardians are also deemed to have provided their consent.  However, prior to the breath or chemical test, the investigating/arresting officer may perform field sobriety tests upon the driver to determine whether it is probable that the driver is under the influence of drugs or alcohol.  One such test is the Horizonal Gaze Nystagmus Test (HGN).

In terms of the field sobriety tests, the HGN test is considered the most accurate and should be administered at a minimum, if the suspect is unable to perform the One Leg Stand or the Walk and Turn tests due to age, size, or physical limitations.

The HGN test relies upon the investigating officer’s observations of the movement of the driver’s eyes as Nystagmus is defined summarily as the involuntary jerking of an individual’s eye.  The HGN test is designed to measure the type of nystagmus that occurs when the eyes gaze to the side.  HGN will occur in any person’s eyes when gazing extremely sideways, but when a person is intoxicated, there are  signs that become apparent in the driver’s eye movements, including: (1) the nystagmus occurs much sooner, that is, the less the persons eyes have to move before the jerking occurs; (2) as the person’s eyes move as far to the side as possible, the greater the alcohol impairment the more distinct the nystagmus will be at the extreme gaze position; and (3) an intoxicated person cannot follow a slowly moving object smoothly with his eyes and eye jerking will be extremely prevalent.  The HGN test is intended to identify and measure these three (3) signs.

The HGN test requires the use of an object for the driver to follow while performing the test, which is usually a fingertip, penlight, or pen.  The object must be held slightly above eye level and twelve to fifteen (12-15) inches away from the driver’s nose.  The investigating officer must inquire and make note of whether or not the driver is wearing contact lenses, but the lenses do not have to be removed for the test.  However, a driver wearing glasses must be made to remove them.

Scoring is performed on three (3) clues that are measured for each eye, giving a maximum of six (6) scoring points for the investigating officer.  If four (4) or more clues are observed, the driver is classified with a BAC above .10%.  The scoring clues include: lack of smooth pursuit (the eyes bounce or jerk as they follow the object); distinct nystagmus at maximum deviation when held for four (4) seconds; and the onset of nystagmus before the eye has moved forty-five (45) degrees.

If you have been arrested and charged with driving under the influence, contact the experienced criminal law attorneys today at 203-221-3100, or by email at  We have the experience and knowledge you need at this critical juncture. We serve clients throughout Connecticut and all of Fairfield County, from Greenwich and Stamford to Westport and Bridgeport.


Anderson, Schweitz, and Snyder, Field Evaluation of a Behavioral Test Battery for DWI, DOT-HS-806-475, September 1983.

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