When law enforcement officials suspect that you have been drinking and driving, they may pull you over and ask you to perform a field sobriety test. The National Highway Traffic Safety Administration recognizes three official types of field sobriety tests. One of these is the horizontal gaze nystagmus test, or HGN. You should understand how this test works before a member of law enforcement asks you to perform it.
What Does ‘Horizontal Gaze Nystagmus’ Mean?
The HGN field sobriety test is primarily an eye test. Nystagmus is the jerking of your eye. As people move their gaze sideways, their eyes may jerk involuntarily. You usually do not notice this motion because it does not affect your vision. Members of law enforcement use nystagmus as a sign of intoxication because this jerking sometimes becomes more obvious if you have been drinking.
How Do Law Enforcement Officials Perform This Test?
There are several steps to the HGN test.
- Preparing for the Test
The officer will usually ask you to face away from the road. The headlights of passing cars and the lights from the police cruiser may cause the nystagmus to be more pronounced, creating a false positive for this test.
Next, the officer typically asks if you wear contact lenses. If you wear glasses, you may need to remove them. Additionally, the officer will ask about any medical conditions you have. Some conditions may exaggerate the horizontal gaze nystagmus, and officers need to take these into account so that they can gauge the accuracy of the test. - Explaining the Procedure
Law enforcement officials should explain exactly how the test works. To perform the HGN test, you have to follow an object with your eyes. This object may be either a penlight or a pen. The officer will hold this object about 12 to 15 inches away from your face and move it from side to side. You have to follow this movement with just your eyes. - Taking the Test
As you perform the test, the officer typically watches your eyes to look for three signs:
– Jerking of the eye before the object moves 45 degrees
– Jerking of the eye after you look sideways for four seconds
– The inability to follow the object smoothly from side to side.
If the officer sees these signs, he or she may charge you with DUI.
How Accurate Is This Test?
Many courts view the HGN test as proof of intoxication because studies from the NHTSA demonstrate that it is one of the most accurate sobriety tests. However, the accuracy rate is about 77% and there are several reasons why you may not pass this past. Eye or neurological conditions sometimes cause nystagmus.
If law enforcement officials charge you with a DUI because of the results of your horizontal gaze nystagmus test, you may want to seek legal help. An experienced DUI defense attorney can help you understand your situation and the options that are available to you. Call the Chambers Law Firm at 714-760-4088 to set up a free consultation.
