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The HGN Test

When suspected of driving under the influence of alcohol, an officer may choose to pull you over and conduct a number of tests. The most common types of tests you may face are known as the Standardized Field Sobriety Tests. These have been developed from the research of the National Highway Traffic Safety Administration and the Southern California Research Institute conducted them. There are three main tests that are known as the One-Leg Stands test, the Walk-and-Turn test and the Horizontal Gaze Nystagmus (HGN) test. The HGN test is one form that will examine the involuntary jerking motion of the eye. It can be an indicator of alcohol consumption and some types of drugs.

In order to conduct this test the officer will first need to be trained in the correct procedure. When administering the test on a suspect, the individual will first be required to remove any eye wear (except for contact lenses). The suspect should be positioned away from the glare of car headlights so that the brightness does not affect the reaction of their eye. Officers will typically use an object during this exam, which is most often a flashlight or a pen. The suspect will be asked to follow the object with their eyes and during this time the officer will be looking for six signs; three in both eyes. The first will be the general smoothness in the eye motion when following the object the officer is holding. Next will be observing when the nystagmus begins when the eye is brought out to maximum deviation. This is the involuntary jerking of the eye when it is brought further out to the side. It is caused by the disruption of the oculomotor control of the eye or the inner ear. The eye may follow the object then begin to lag, and then jump forward to correct falling behind. The officer will hold the object out to the side for around four seconds to make sure that the movement of the eye was not the reason for the nystagmus.

The last clue that they will be looking for is when the nystagmus occurs. The officer will begin to move the object they are holding out to the side of the individual's shoulder and notes if the nystagmus occurs before the object is taken out forty-five degrees. These tests are not always accurate and they may be administered incorrectly, leaving many innocent individuals facing charges they do not deserve. If you have found yourself under investigation for drinking and driving charges you may be able to fight them. Turn to a Pasadena criminal defense lawyer from The Law Offices of Matthew Cargal for over 20 years of experience!