California (HGN) Horizontal Gaze Nystagmus Test

The Horizontal Gaze Nystagmus (HGN) is just one of many field sobriety tests utilized by police officers during a DUI investigation. Police officers and prosecutors believe that the HGN test is a successful method for helping determine whether or not a person has been drinking and driving. However, many medical experts would disagree with this notion.

Nystagmus is an involuntary jerking of the eyes, which can be brought on by alcohol consumption. However, many people suffer from a natural nystagmus and police officers are not trained on how to recognize the difference between the two.

During the HGN, a police officer will use a stimulus (usually a pen with a light). The officer will ask the person to follow the stimulus with their eyes without turning their neck or head. If a person’s eyes start to oscillate before the eyes reach a 45 degree angle, alcohol consumption may be to blame. The officer will also look for how smoothly the person’s eyes are able to follow the stimulus. When the eyes are at maximum deviation, the officer will study them to see if they are jerking.

There are many problems associated with this scenario. First, the officer is merely estimating the angle at which the eyes begin to jerk (if they jerk at all). Secondly, police officers are not trained medical professionals. Police officers must also follow proper protocol when administering the HGN. For example, the stimulus must be held at a comfortable distance away from the person’s eyes.

Natural elements such as high winds or dust can also have a negative impact on a person’s test results. Police lights and vehicles speeding by can also confuse and distract a person’s vision, which may cause them to fail the HGN.

For these reasons and more, it is imperative that you speak with an experienced DUI defense attorney. An attorney will review your HGN test results and if there are any weaknesses in the prosecution’s case, the attorney will expose them! There are many defenses to the HGN. Before you plead guilty, contact a DUI defense lawyer right away.