The Horizontal Gaze Nystagmus Test Is Also Known As HGN In Florida

Interviewer: Moving on to the next one here; the Horizontal Gaze Nystagmus test.

Jay Arnesen: Horizontal Gaze Nystagmus test, it’s commonly known as HGN.Now, HGN is interesting too because there’s a separate certification that officers are required to get if they’re going to have any basis of knowledge of this test and the HGN has been litigated for years, if not decades, in almost all of the courts that I know of as to its admissibility, as proof of intoxication against an individual at trial.First and foremost, this is a test that’s been developed by the National Highway Traffic Safety Administration.  In this particular test, the officer conducts something to this effect: He tells the subject, “I am now going to check your eyes”, but in fact the officer is not checking one’s eyes but he’s looking for signs of impairment.  What he’s looking specifically for is Nystagmus.

Nystagmus is the Involuntary Jerking or Balancing of the Eyeball Over Which a Subject Doesn’t Have any Control

Nystagmus is an involuntary jerking or balancing of the eyeball over which a subject has absolutely no control especially if they’ve consumed alcohol.  And the consumption of alcohol and other depression limits the ability of one’s brain to control their eye muscles; so therefore, you’ll see a Nystagmus or bouncing.Now, when you see this on the street or on videos on TV, you’ll see an officer hold up a pen light and they’ll tell the subject, “Hey, listen.  Keep your head still and just follow the tip of my pen with your eyes”, and he’ll bring the pen over to the right, he’ll bring the pen over to the left and then, you could see that he holds it out.  When he’s holding it out there, the person’s eyeballs, if their head is straight, is actually in the corner of their eye socket looking at the stimulus, the penlight.

If A Subject is Under the Influence of Alcohol, the Eyeballs will Bounce Back and Forth Which is Known as Nystagmus

If they’re under the influence of alcohol, the officer will observe the eyeballs bouncing back and forth, which again is known as Nystagmus. The officer is also tracking the person’s eyes when they’re moving back and forth. So, any lack of smooth pursue while tracking the object is noted by the police officer, any distinct Nystagmus at what’s called maximum deviation is going to be noted by the officer and any distinct Nystagmus, a maximum deviation, again, that’s when the officer holds the penlight off to the side, holds it there for a period of time and that’s maximum deviation.  And if the officer notices the bouncing of the eyeballs, he’s going to note that in his report.

There May be Other Factors than Alcohol That Contribute to Nystagmus

Interviewer: Are there any contributing factors to that like the HGN test that it may be, perhaps may not always be due to alcohol?

Jay Arnesen: Absolutely, yes.  There are many different forms of Nystagmus that affects one’s eyes that have nothing to do with alcohol or drugs and almost skies the limit.  People just have natural Nystagmus for whatever their eye conditions are, it could be nearsightedness or farsightedness as well as many other auricular or nerve or eye diseases or sicknesses they may have.And obviously, an officer’s not going to be trained to delineate between Nystagmus from alcohol or Nystagmus from an eye problem, and that’s a very, very important thing that we, as defense attorneys, will ask our client about to see if they have any forms of eye impairment that had nothing to do with the alcohol consumption itself.

Environmental Factors Can Affect the Performance of a Subject in a Field Sobriety Test

Interviewer:Can there be other outside factors not necessarily like an eye issue or something that someone has, some sort of eye illness but something along the lines of, like I’m thinking — if I was in that situation, reflections of mirrors, lights in the middle of the night, cars flashing by, how they’re able to conduct that when that’s going on?

Jay Arnesen: I think that’s a very important question and that’s something that we tend to ask the officer about where and how each of the tests were conducted because flashing lights, people walking on the streets, other cars passing are all distractions that could cause someone to lose their concentration.When a subject is performing standardized field sobriety tests, whether it’s the Horizontal Gaze Nystagmus, the Walk and Turn, or the One Leg Stand, the optimal conditions to perform those tests are going to be in a dry, lit, flat area, free of debris, no sirens, no lights, no traffic but that’s often not the case because many times, people are caught driving on a busy roadway.So, there are many distractions that we need to try to rule out in order to get a clean or a valid sobriety test.  Officers just don’t have the ability to weed that out.  There’s nothing in the NHTSA guidelines that’s going to help an officer decide if a particular indicator was hit, if that had something to do with an outside factor.

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