Just how Accurate Is the Horizontal Gaze Nystagmus Test?

If you’ve ever been stopped under suspicion of drunk driving, then you may have taken the horizontal gaze nystagmus field sobriety test. This is also called the HGN and is among the most common standardized field sobriety tests.

The test is administered by a police officer to determine if you’re impaired or affected by alcohol or other substances. This test is one of the more accurate field sobriety tests, but it is still only around 77% accurate when determining if a person is impaired — and then only under ideal conditions, not when a subject is on the side of a road, in traffic. That’s something to remember if you fail it. Failure doesn’t necessarily mean you’re drunk.

How Does the Horizontal Gaze Nystagmus Test Work?

The HGN test watches for the jerking of the eyeballs. To administer the test, the officer will hold a small object, like a pen, around one foot to 15 inches away from your nose. They’ll move it from side to side slowly, asking you to follow it with your eyes.

The officer is doing all of this to watch and see if you can trace the object with your eyes smoothly. They also want to see if your eyes jerk or bounce. Finally, the officer will look for any jerking of your eyes when you’re looking to the side for a prolonged period of time.

If the officer believes that you’ve failed the test along with others that he or she gave, then you may be arrested. This is a test worth fighting, though, since there are many medical conditions, including neurological disorders and eye conditions, which could impact the results of the test.

If you’re arrested for drunk driving because of failed field sobriety tests, your attorney will help you look into ways to defend yourself in court.