Standard Field Sobriety Tests: Why Horizontal Gaze Nystagmus Test is Bogus

Posted by: Russell Hebets       08-May-2015       (0) Comments        Back to Main Blog

In Colorado and the majority of other states, police officers trained to administer standard field sobriety tests (SFST’s) to a suspected drunk driver. In this blog, we are going to examine one of them- the Horizontal Gaze Nystagmus test (HGN), and why it is a bogus test that cannot be relied on to determine a person’s intoxication.

Why You Should Never Perform SFST’s

Before we begin our discussion, let’s talk about roadside tests generally. This blog is not designed to tell you how to “beat” this so-called test. We advise our clients to never subject yourselves to these SFST’s in the first place. There are several reasons for this. First of all, the tests are extremely subjective. The only person who decides if you failed is the police officer standing in front of you who already thinks you’re drunk. By the time the officer has you performing these tests, he has most likely already made the decision arrest you; these tests are being used against you, not for you. Second, the tests are voluntary, meaning there is no penalty for refusing to complete them. Don’t give the officer more ammunition to use against you. Finally, these tests are designed to make you fail. I know that many of you may be thinking, “But Colin, these cops are just checking to see if I’m sober, and if I nail these tests, they’re gonna let me go, right?” The problem is these tests are like a rigged carnival game. The cop doesn’t tell you everything they are looking for, and when you are standing on the side of the road with a cop watching your every move with a Mag-Lite in your eye, you are most likely doomed to fail. Many sober people wouldn’t be able to pass these tests. You are always better off politely declining to take them.

What is the Horizontal Gaze Nystagmus Test?

That being said, let’s now single out the HGN. Here is a video that demonstrates this test. The officer has the suspect stand in front of him. The officer then takes a stimulus, commonly a pen or finger, and passes it in front of the suspects eyes, looking for nystagmus. Nystagmus is an involuntary jerking of the eye that can be caused by alcohol consumption. The officer looks for nystagmus, and if it is present, they observe whether it appears at all angles when the stimulus gets passed back and forth between the eyes.
Right from the get go, the cop misleads you. They are trained to tell the suspect, “I am going to check your eyes.” That’s it. This leads the suspect to think that all they have to do is follow pen with their eyes, and they are home free. The cop is not required to explain what he’s actually looking for, which is the jerking of the eyes. Dash cameras in patrol cars are not sharp enough to zoom in on a person’s eyes when they are on the street doing these tests, so there is no way to check whether the observations are correct. In Colorado, many patrol cars don’t have dash cameras to begin with, so there is no way to check to see if the officer administered the test correctly and provided the proper instructions. In short, you are at the mercy of the officer’s subjective evaluation of how you perform.

There Are Many Causes for HGN other than Alcohol

Cops are trained that alcohol causes nystagmus, and that if it is present, the suspect is drunk. However, there are about many other causes for it, including hypertension, excessive caffeine, aspirin, use of pain killers, or a prior head injury. There are often times legitimate medical reasons why nystagmus may exist in the eyes.

The point here is that the HGN test, like the other SFST’s, are not reliable indicators of a person’s sobriety, and they can be manipulated by the police to make it seem like a person is more intoxicated than they really are. Don’t drink and drive. But if you find yourself in a situation where an officer is wanting to put you through this battery of tests, the safe move is to politely decline. The officer may not like it and you could be arrested, but you are protecting yourself in the long run.


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DISCLAIMER: The information you obtain at this site is not, nor is it intended to be, legal advice. You should consult an attorney for advice regarding your individual situation. We invite you to contact Hebets & McCallin, and welcome your calls, letters and electronic mail. Contacting us does not create an attorney-client relationship. Please do not send any confidential information to us until such time as an attorney-client relationship has been established.