Driving Under the Influence in LA or OC: What Is the HGN Test?

If you are ever stopped on suspicion of driving under the influence in Orange County the law enforcement officer making the stop will likely put you through a series of “field sobriety tests”, or FSTs. These tests are used to help the officer determine if you are intoxicated, or under the influence of drugs or alcohol. One of the tests the officer will likely perform is the Horizontal Gaze Nystagmus, or HGN, test. Because the officer, as well as courts, will often rely heavily on the results of the HGN test it is helpful to understand what the test measures and how the test should be performed.

If you have ever seen a police officer asking a suspected drunk driver to “follow the pen” on one of the many reality television shows that is an example of the HGN test. Though you may have assumed that the officer was just testing how well the suspect could follow directions, there is actually much more to the “HGN”. The term “horizontal gaze nystagmus” refers to a lateral or horizontal jerking when the eye gazes to the side. The human body functions in such a way that when alcohol, and some other central nervous system depressants, enters the blood stream your brain has a hard time controlling eye movement. As a result, the more intoxicated an individual is the more likely he or she will show signs of HGN. When the pen is held at a 45 degree angle from your eye your peripheral vision is triggered. Without alcohol in your system your eye can see at that angle without “bouncing”; however, the more alcohol (or depressants) you have in your system the less able you are to look at the pen without “bouncing”.

Is the HGN Test Accurate?

The big question if you have been charged with driving under the influence in Orange County is whether or not the HGN test is accurate. The National Highway Traffic and Safety Administration, or NHTSA, has concluded that it is accurate when administered properly. Even if the test is administered properly the results are subjective. An officer is looking for jerking and/or bounding during the test; however, the results are based on the officer’s opinion, unlike a breathalyzer that provides an actual readout. There are a number of factors that impact the accuracy of HGN results. If you were given an HGN test and were subsequently arrested for DUI based on those results contact an experienced Orange County DUI attorney to discuss your arrest and pending charges.