Fresno and the rest of California have been using different methods to test a driver's field sobriety for decades. One of the big three tests currently used is referred to as HGN. Horizontal Gaze Nystagmus (HGN) is one of the few evaluations that has been certified by the NHTSA (National Highway Traffic Safety Administration).
Although this test has been certified by the agency, that does not mean that is an effective means of determining a driver's sobriety. Here's a quick overview of the test:
- What is the officer looking for? The officer will be evaluating the involuntary jerking of your eyes. It is generally assumed that a sober driver will display smooth eye motions and an intoxicated driver will tend to demonstrate a high amount of jerking. It is also assumed that the jerking will appear at fewer eye angles.
- What does the test entail? While the test is being performed, the officer will have the driver move his eyes from side-to-side. The officer will instruct the driver to follow some object, usually a pen, back and forth.
- What are the clues? The officer is looking for three distinct things. She wants to see whether the eye cannot follow the object with a smooth movement, whether the jerking is clearly noticeable when the eye is at maximum deviation, and whether the onset angle of the jerking is within 45 degrees of center.
So, now that you know what the format is, let's discuss how the HGN test can lead to inaccurate results - results that may cause you to be arrested!
- Weather: Generally, HGN is performed during the late night hours, when it is dark. In addition, there may be high winds or rainy conditions that will cause a driver to perform poorly on the exam. Unfortunately, officers do not take these circumstances into account and the driver will still fail.
- Medical: A driver may have a condition that causes him to perform poorly on the exam. In these cases, the officer is usually unaware or uninterested in the condition and whether that is the true cause of the driver's failure on the exam. These medical conditions may include diabetes, the flu, and ear infections.
- Biological: Alcohol can cause a person's eyes to react a certain way, but so can other legal substances. The driver's jerking can be influenced by things like nicotine, aspirin, and caffeine.
- Environment: Often times, an HGN evaluation is administered on a busy street with a lot of traffic. It is human nature to take interest when you see a cop's flashing lights on the side of the road. This can lead those passing by to slow down, speed up, flash headlights, or even honk when passing the driver who is performing the test.
All of these factors and situations can add up to you being unfairly arrested for DUI in Fresno. An officer should be understanding of these circumstances and take them into account when administering the test, but that is most often NOT the case! Officers are applauded when DUI arrests are high and it usually doesn't matter whether those arrests were lawful.
If you have been arrested and charged with DUI in Fresno, do not hesitate to call my office as soon as possible.