DUI and the HGN ("follow with your eyes, not your head") Test

April 29, 2013

There is probably no sinking feeling that matches getting pulled over after having had a bit too much to drink. As often as people will have thought, only moments before, that they were okay to drive, there is a sudden concern, if not realization, that their own assessment may have been off a bit as they put the car in park and wait for the police officer to approach. No one can really smell alcohol on his or her own breath, but everyone knows when he or she is unable to walk a straight line.

There is, of course, a lot to a Michigan DUI traffic stop. As a Detroit DWI attorney, I've written rather extensively about many, if not most, aspects of the traffic stop. The fact is that you could fill several volumes about the various facets of being pulled over for suspected drunk driving. To keep our mission manageable here, and to keep your attention, as well, we'll limit our ambitions a bit and take a brief look at one small part of a DUI traffic stop and the field sobriety tests, the horizontal nystagmus gaze (HGN, or as often referenced by the police in the Metro-Detroit area of Macomb, Oakland and Wayne Counties, the "horizontal NSG") test. This is the test where the officer asks a person to keep his or her head still, and follow an object (often a finger, or a pen) using only their eyes. This test has a remarkable capacity to detect that a person is impaired by alcohol.

HGN 1.2.jpgThe HGN test measures how smoothly a person's eyes follow an object moved from one side of their field of vision to the other. As it turns out, absent any of a few particular medical conditions, a sober person's eyes will follow such an object rather smoothly, like a perfectly round marble rolling on a piece of glass. Alcohol affect the movement of the eyes, and as a person becomes more inebriated, his or her autonomic motor functioning likewise become impaired, meaning that they eyes will "jump" (kind of like that same marble being rolled over a sheet of grainy sand paper) and not track smoothly. This is completely outside of a person's conscious control, and no matter how sober or drunk someone may become, they never notice this from their own perspective.

It would be impossible to appropriately summarize the science behind the HGN test beyond pointing out that even the American Optometric Association has passed a resolution endorsing it as an effective test for alcohol impairment. The HGN test is generally believed to be the most reliable of all field sobriety tests. The flip side is that it is also almost generally impossible to independently verify, leaving proof of a person's performance on the HGN test as almost entirely a matter of believing what the police officer says (or writes in his or her report), or not. Not every police officer can administer an HGN test, however. In order to do so, the officer has to be specially trained to administer it. Given it's high degree of reliability and ease of administration at the side of the road, it's little wonder that more and more police officers are receiving this training.

The few exceptions to the scientific reliability of the HGN test as evidence of alcohol impairment don't often occur in real life DUI traffic stops. If you have a brain tumor (and then you'd have to prove that it's the kind that would affect your performance on an HGN test), a brain disease, or an inner ear disease, then this should be explored as a defense. Most conditions that would affect a person's performance on an HGN test would likewise prevent them from driving in the first place. Even then, the likelihood that such a person would be driving, and also drinking (remember, it's not illegal to drink and drive, it's only illegal to drink too much and then drive) is rather remote.

For a moment, let's skip all the lawyer-talk exceptions and exclusions and limitations and focus on the "real world." In the real world, if you're pulled over, and the police officer has you out of the car taking field sobriety tests, it's rather likely you've had something to drink. The National Highway Traffic Safety Administration has sanctioned, or validated only 3 field sobriety tests: The HGN, the heel to toe walk, and the standing leg raise. While many police officers do alphabet and counting tests, neither of them, nor any other test beyond the 3 approved by the NHTSA, really have any real legal weight.

The point I'm driving at is that if you are standing at the side of the road and a police officer is in front of you instructing you to follow his or her finger, or pen, and not move your head, and then you're arrested for a DUI and thereafter provide a breath sample over the limit, you need to really start thinking about how to make the situation better beyond just wishing it away. Sure, anyone would want the whole thing to just "go away," but then again, everyone would want to be a millionaire, too. Just wanting something doesn't make it happen. In other words, by the time you're taking an HGN test at the side of the road, there is a really good chance that are you are going to be arrested for a DUI. If you're reading this, that chance has already likely happened.

While the landscape of DUI lawyers is full of great salespeople, the landscape of real life DUI cases tells a very different story. In 2011, there were 54, 291 DUI and related arrests in Michigan. Out of ALL of those, only 95 resulted in a "not guilty" verdict after a full-blown trial. This seems to be painfully overlooked by those attorneys who appeal to potential clients by focusing on what "could be" wrong with any given DUI case.

Let's put that in perspective. If you wound up with a disease and discovered that of the 54, 291 cases diagnosed last year, only 95 people were cured, and all the rest died, you'd have to start thinking about making some final arrangements. In terms of success, 95 out of 54, 291 equal .17%. Put the other way, that means that in 2011, of the 54, 291 people arrested, for some kind of DUI, 99.83% did not win by going to trial. There wasn't something "wrong" enough with those cases to convince a jury.

Yet for all that doom and gloom, there is some good news. When we examine the video from a DUI traffic stop (in this article, we're concerned with the HGN test, but to put things in perspective, the first thing anyone should be looking at in any such case is the reason, meaning probable cause, for the stop) and focus on the field sobriety tests, particularly the HGN test, it is important to remember that, while the video may show a person doing well (or not) on the heel to toe and standing leg raise tests, it almost never shows how well or poorly a person did on the HGN test. There is no way a "dash-cam" mounted inside a police car will ever be able to focus on a person's eyes. This means that, at the end of the day, in almost all cases, the best evidence, and really the only evidence of a person's performance on an HGN test is limited what the officer writes in his or her report.

This tends to become pretty worthless, however, if the police car video shows Dan the Driver unable to walk heel to toe, or to do a standing leg raise without flailing about. Here, also, is where things like an alphabet or counting test can help the police. If Dan the Driver is slurring his words, or is demonstrably unable to follow clear and simple directions ("count backwards from 96 and stop at 87"), then it only makes him look all the more drunk. We can debate the technical legalities of this all day long, but this explains why, in the real world (which is exactly where anyone's DUI will be decided) out of over 54,000 DUI arrests in 2011, only 95 resulted in a verdict of "not guilty."

It is important to note that the HGN test is not used to show that a person was drunk, or how drunk they were. Instead, the HGN is used for the purpose of showing that the police officer did, in fact, have probable cause to arrest someone for drunk driving (and thereafter administer a breath test). This means that any good DUI lawyer is still going to carefully review the whole case to make sure there was sufficient probable cause to make the traffic stop in the first place, and otherwise make sure that there is legally admissible and sound scientific evidence (meaning breath or blood test results) that a person was actually over the limit at the time they were driving. To put it another way, the HGN test can support your arrest, but a lot more is needed for a DUI conviction.

The HGN test is a powerful field sobriety testing tool. If you've had to take it, then you know that it almost always precedes a ride to jail. While the test itself cannot be used to prove that a person was over the limit, it can be and is used to establish probable cause for a DUI arrest. There is a lot to all of this, and this article can't even being to scratch the surface beyond perhaps throwing some light upon why this test is used, and the role it plays in a DUI charge.