HGN Test
There are three standardized field sobriety tests that are approved by the National Highway Traffic Safety Administration (NHTSA): the horizontal gaze nystagmus (HGN) test, the walk-and-turn test, and the one-leg stand test. If you have recently been charged with drunk driving, you were probably asked to take one or more of these tests, as field sobriety tests are used to determine whether there is probable cause to make a DUI arrest.
What is horizontal gaze nystagmus? Nystagmus is an involuntary jerking or twitching of the eyes that naturally occurs when a person looks to the side without moving his or her head (typically at a 45 degree angle). A person who experiences nystagmus is not aware that it is occurring.
There are several factors that may cause nystagmus, with alcohol consumption being one of them. As a result, a police officer may administer an HGN test in order to determine if the driver is under the influence of alcohol. The test may also be used to determine whether the driver is under the influence of barbiturates and depressants.
To administer the test, the officer will ask you to follow an object, such as a flashlight or the officer’s finger, with your eyes while keeping your head still.
During the test, the officer is looking for three clues of impairment in each eye: whether or not the eye can follow the object smoothly, if nystagmus sets in before reaching 45 degrees of center, or if the jerking becomes distinct when the eye is at maximum deviation. If the officer observes four or more clues between both eyes, he or she may arrest the suspect for driving under the influence.
Of the three standardized field sobriety tests, the HGN test is known as the most scientific; however, this doesn’t mean that the test is perfect. There are hundreds of conditions that can cause nystagmus besides alcohol and drug consumption. For example, certain medications, vision problems, neurological disorders, and brain tumors may also cause nystagmus.
If you have recently been charged with DUI after failing the horizontal gaze nystagmus test, you should contact a skilled DUI defense lawyer as soon as possible. Your lawyer can determine whether the test was administered properly or if you have an underlying condition that may have caused you to fail the test.
