Listen to this Page:
Quick Navigation:
- What is Horizontal Gaze Nystagmus / HGN Test?
- Lack of Smooth Eye Pursuit Side-to-Side
- Distinct and Sustained Nystagmus at Maximum Deviation
- Onset of Nystagmus Prior to 45 Degrees
- How Many “Clues” does it take to Fail the HGN Test?
- Vertical Nystagmus – Not one of the Clues
- What can Affect the Reliability of the HGN Test?
- How Accurate is the Horizontal Gaze Nystagmus Test?
- Can You Beat the HGN Test?
When facing a DUI stop in Arizona, one of the key assessments law enforcement may utilize is the Horizontal Gaze Nystagmus (HGN) Test. A cornerstone in DUI investigations, the HGN test’s validity and administration are as critical as they are complex. This evaluation is more than a roadside inconvenience; it’s a scientifically rooted procedure that carries significant weight in the determination of impairment.
The HGN test is specifically designed to detect impairment by observing the involuntary jerking of the eyes—a phenomenon known as nystagmus.
Here in Arizona, police officers trained in its administration use this test to seek out subtle signs of intoxication that may not be otherwise apparent.
In the following sections, we will examine the mechanics of the HGN test, scrutinize its reliability, and consider the factors that can influence its outcomes. An exploration of Arizona Revised Statute will also be provided to contextualize the legal framework surrounding this test.
According to research by the Southern California Research Institute, the HGN test has a reported accuracy of 77% in identifying individuals with BAC levels at or above 0.10. However, this leaves a noteworthy margin for false positives and interpretation errors that must be carefully considered in legal proceedings.
Need Help Beating an Arizona Drunk Driving Charge?
Our Arizona DUI Attorneys are Available to Talk Now.
Or, Continue Reading Below About:
What is the Horizontal Gaze Nystagmus Test and How Officers Use it for a DUI?
What is the HGN Test, or Horizontal Gaze Nystagmus Test?
If you are pulled over for DUI in Arizona, and an officer suspects that you may have been drinking, chances are the officer will administer the Horizontal Gaze Nystagmus test.
Mainly referred to by its acronym, the HGN test is part of a battery of three standardized field sobriety tests used by police officers in Arizona and throughout the United States for DUI investigations.
The HGN test was developed by the National Highway Traffic Safety Administration (NHTSA) as a tool for officers to detect impaired drivers. This test consists of an officer moving a stimulus, most often a pen or their finger, back and forth across your face as they watch how your eyes track the stimulus.
Police officers are looking for nystagmus, which is an involuntary jerking of the eyes.
Officers are taught during training that alcohol and certain drugs will cause pronounced nystagmus that is visible to the human eye. We will often hear officers tout that the HGN test is the most important and reliable test of the three-test battery of field sobriety tests.
Officers will often say that a particularly athletic person may be able to pass the balancing, or divided attention, field sobriety tests, but since nystagmus is involuntary, a person will not be able to compensate for it by being athletic.
In fact, we recently reviewed body camera footage of an officer telling our client that “the eyes don’t lie,” something that the officers are told in training. Unfortunately, it seems that particular officer didn’t learn much more than that phrase during his training, as he called the test the horizontal “guise” nystagmus test and his administration of the test was not done in a standardized manner, making his findings questionable at best.
Although the NHTSA standardized field sobriety test, or SFST, training manual states that the techniques of the tests can readily be grasped by “anyone of average competence,” officers are often quick to overstate the rigor of their training on the stand.
Many of our clients will tell us that they believe they “passed” the field sobriety tests, only to learn that the officer wrote in his report that the person showed multiple clues of impairment.
Part of the misunderstanding is that the officers do not tell you how the tests are graded. If the officer tells you to follow a pen with your eyes, and you are able to do that, you may believe that you passed the test. What the officer is really looking for are three clues for each eye, for a total of six clues on the HGN test.
The clues officers look for in an HGN Test are:
- Lack of Smooth Pursuit
- Distinct and Sustained Nystagmus at Maximum Deviation, and
- Onset of Nystagmus Prior to 45 Degrees.
Lack of Smooth Eye Pursuit
During this portion of the test, the officer is looking at a person’s eyes to see if they follow the stimulus smoothly or if there is a jerking or bouncing motion as the pupils move across the horizontal plane.
Officers will describe a lack of smooth pursuit as similar to windshield wipers skipping across a dry windshield.
To look for lack of smooth pursuit, the officer must start with the left eye and hold the stimulus approximately 12-15 inches from the subject’s nose. The stimulus is also supposed to be held slightly higher than the subject’s eye level.
The officer starts with the stimulus in the center of the subject’s face and then moves the stimulus out beyond the subject’s shoulder. This should take approximately two seconds.
Next, the officer moves the stimulus across to the other shoulder, keeping a distance of 12-15 inches in front of the subject’s face. This “pass” should take approximately 4 seconds.
The officer must do two passes for each eye to look for lack of smooth pursuit. If lack of smooth pursuit is present in each eye, the officer marks 2 clues.
Distinct and Sustained Nystagmus at Maximum Deviation
For this clue, the officer will move the stimulus from the center of the subject’s face and out to the side until the eye is looking as far to the side as possible. The officer should not be able to see any white between the iris and the outside corner of the subject’s eye.
The officer must hold the eye at that point for a minimum of four seconds, but not longer than 10 seconds.
The officer is looking for “distinct” and “sustained” nystagmus, which is somewhat subjective and not clearly defined.
If the officer determines that the nystagmus is distinct and sustained, then the officer will mark down 2 clues, one for each eye.
Onset of Nystagmus Prior to Forty-Five Degrees
During this portion of the test, the officer is looking to see if nystagmus is present prior to bringing the eyes to a 45-degree angle from looking straight forward. The officer will estimate this 45-degree angle by moving approximately 15 inches to the side starting from the center of the face.
The officer should still see some white between the iris and the corner of the subject’s eye and the stimulus should be slightly beyond the subject’s shoulder at 45-degrees.
It should take the officer approximately four seconds to move the stimulus to slightly beyond the shoulder. If the officer sees nystagmus prior to 45-degrees, he will mark a clue for each eye.
How Many Clues Does It Take to Fail the HGN Test?
There are a total of 6 clues on the HGN test, 3 clues for each eye. Officers will tell you that this is not a “pass or fail” test. However, at a certain number of clues they will consider you impaired—and arrest you—which sure sounds like “failing.”
An officer will consider a person impaired, and above the legal limit of .08, if they exhibit 4 or more clues on the test.
The clues on the HGN test are cumulative, meaning that they should be exhibited in order. Distinct and Sustained Nystagmus at Maximum Deviation should only be present if the officer also observed a Lack of Smooth Pursuit.
Similarly, Onset of Nystagmus Prior to 45-Degrees should only be present if the officer also saw the first 4 clues. On the subject of clues, it is possible for someone to have an odd number of clues (1, 3, or 5) if they only have one eye or if they have a serious medical impairment.
Vertical Nystagmus – Not One of the Six Clues
You may recall that after the officer moved the stimulus from side to side, that he raised the stimulus up above your head in a vertical manner. Although vertical nystagmus is not one of the 6 clues, officers will often check for vertical nystagmus at the end of the HGN test.
Vertical nystagmus, much like horizontal gaze nystagmus, is an involuntary jerking of the eyes. However, it is present when the eyes are looking up, rather than to the left or right.
An officer will claim that the presence of vertical nystagmus is an indicator that the subject is extremely intoxicated, meaning they consumed a large amount of alcohol for their individual tolerance.
What Can Affect the Reliability of the HGN Test?
There are a number of issues that can occur during the administration of the HGN test. First, prior to beginning the test, the officer should ask the subject about any medical issues that could affect the reliability of the test.
The officer should ask the person if they have had any head or eye injuries. If a person was involved in a car accident, there is a possibility that they sustained a head injury, especially if the airbags deployed.
Yet, in many cases, an officer will still attempt to conduct the HGN test. An officer should also inquire as to whether the person has been diagnosed with natural or resting nystagmus prior to attempting to administer the HGN test. If a person’s eyes do not track equally, or their pupils are unequal in size, this could be the result of a serious medical issue and the officer should call for medical assistance rather than conducting the HGN test.
It is important to note that there are 47 types of nystagmus. Officers are taught that alcohol, inhalants, PCP, and other central nervous system (CNS) depressants such as Xanax will enhance nystagmus.
However, there are many other causes of nystagmus that are not attributed to alcohol or drugs. In fact, it is commonly said that everyone has nystagmus, but to such a small degree that it cannot be seen by the human eye.
Some other causes of nystagmus include
- inner ear problems
- caffeine
- nicotine
- aspirin
- head trauma
- eye muscle fatigue
- antihistamines
- hypertension
- sun stroke
- some prescription medications
It is possible that someone could exhibit nystagmus from something entirely unrelated to alcohol or illicit drugs.
The way that the HGN test is administered can also affect the reliability of the tests. The officers are trained to turn off their emergency lights prior to conducting the test so that they are not visible to the subject. Similarly, they are told to face the subject away from rapidly moving traffic.
Rotating lights, strobe lights, and rapidly moving traffic can cause a person’s eyes to momentarily fixate on the rapid movement as it comes in and out of the person’s field of vision.
This momentary fixation is called optokinetic nystagmus, which an officer could mistake for horizontal gaze nystagmus.
If an officer does not follow the standardized instructions for the HGN test, they may not be able to properly view nystagmus. For instance, if the officer’s passes across the body are shorter than 4 seconds, the officer would not have viewed the eyes for long enough to determine whether there was a lack of smooth pursuit.
If the officer holds a person’s eyes at maximum deviation for longer than 10 seconds, there is a risk of eye muscle fatigue, which can cause nystagmus.
How Accurate is the HGN Test?
From 1977 to 1983, NHSTA commissioned the Southern California Research Institute (SCRI) to conduct studies on the field sobriety tests, including the HGN test.
Per the SCRI studies, the HGN test was supposedly only 77% accurate in determining BACs at or above .10. Since that time, NHSTA has modified its findings to fit the legal limit of .08.
Even so, NHTSA’s own research showed that the test was inaccurate 23% of the time. Further studies have been commissioned by NHTSA, with the most recent study being the 1998 San Diego study.
This study boasts that the HGN test is 88% accurate. This statistic, however, ignores the underlying data that points to a rate of false positives much higher than the purported 12% rate of inaccuracy.
Can You Beat the HGN Test?
While officers are trained to parrot the idea that the HGN test is the most reliable and accurate field sobriety test that they administer, there are a number of pitfalls that can discredit the results of the test.
From alternative causes of nystagmus, to picking apart the “research studies” that have been conducted, the Phoenix DUI attorneys at Colburn Hintze Maletta, PLLC, have successfully cross-examined countless police officers and expert witnesses on the subject of HGN.
We have extensively researched the subject of HGN, from analyzing the police departments’ own NHTSA standardized field sobriety test manuals (for both the instructors and the students), to reading and scrutinizing the studies that have been conducted regarding the HGN test, to consulting with medical experts and toxicologists, the attorneys at CHM Law are well equipped to attack the findings of an HGN test.
Not only have we done our research, but we have put our strategies to the test during numerous DUI jury trials with successful results.
Our Phoenix DUI lawyers have even been sought out by other Arizona criminal defense attorneys for advice and tactics to rebut the HGN test during trial.
While every case is unique and past performance is not a guarantee of future success, Colburn Hintze Maletta, PLLC, has the tools and experience to go up against even the best DUI officers and prosecutors. Call our Phoenix DUI lawyers at (602) 825-2500 for a confidential and free consultation.
David Maletta is a widely respected criminal defense attorney with over 23 years of experience and has worked on over 1,000 cases and has successfully won over 100 jury trials. David graduated from Northern Arizona University, Magna Cum Laude in 1993 with a degree in Psychology. Shortly thereafter, he earned his Juris Doctor degree from Seton Hall University School of Law in 1998. He has extensive experience in criminal and DUI matters, homicide, sexually-based offenses, domestic violence, white-collar crimes, and various misdemeanor crimes.
Always Available 24/7 for Legal Help
Schedule an Appointment Today!
Call Us Now to Speak with an Attorney (602) 825-2500
Real Client Reviews
Below are just a few of what our clients have to say!
“Listens to every request that you make on a case”
I honestly just want to let it be known to any and everyone looking for an attorney on a case. Whether it be DUI, possession, or your every day to day traffic violations where you need representation attorney Tim Hintze is your man. You have to respect a man that listens to every request that you make on a case and he gets in there and gets it done. Tim has my respect as an attorney and being a well-rounded representer. From him being honest on the possibility and options for your case to him being easy to work and communicate with via over the phone or face to face Mr. Hintze is working it out.
Ben - AVVO Review
“Because of Darin I got my daughter back”
Before I hired Darin I went through a total of 3 different attorneys in two different states fighting a jurisdiction battle, when my daughter was taken to a different state. It was a very difficult decision to switch attorneys at one of the most difficult, time sensitive and important times in my case, but I’m very glad I did. Upon receiving my file from previous attorneys Darin came very familiar with my case quickly. Like other people have explained he took the time to lay everything out and explain how the process was going to proceed and what to expect and continued to do this as new issues arrived. He is also very quick at responding to emails and phone calls. My case was getting close to trial as told by my previous attorneys, I did not want to go to trial as I know this is very costly (most attorneys will convince you that you need to.) Darin knew my situation, fought for what was right and got the results I wanted while avoiding a costly trial. He is extremely knowledgeable in the Child Support Guidelines as well. Because of Darin I got my daughter back. I would highly recommend him and would hire again for any future issues. Thanks Darin!
Chris - AVVO Review
“Nothing but good things to say about my experience.”
I have nothing but good things to say about my experience working with David Maletta. I was in a very high-stress situation facing a pending DUI charge. He doesn’t know this, but I actually interviewed 5 potential lawyers, and he was the most optimistic of all of them. He took over and handled everything, and now I don’t have to live with a DUI. Thank you so much for everything! Highly recommend them to anyone looking for legal help.
Lauren Koontz - Google Review
“I still have a clean record to this day.”
One piece of advice for people who are charged with anything in Arizona is to hire a great lawyer because the state does not care if you’re innocent or not. The Arizona legal system will try to ruin your life. A couple of years ago I was the victim of an antisemitic hate crime when a guy named Billy, who had a history of drug and alcohol issues and was thrown out of the Navy for being violent, decided to attack me after drinking all day in Old Town (Sunday funday) over a pointless argument over whether it’s better to buy homes immediately post-recession or during the 10th year of a bull market run which was his argument. The disagreement led to Billy making several anti-semitic comments and assaulting me, which led to me beating up billy. Billy and his friends then went to the police and lied to try to get me thrown in jail for months for assault while getting 10s of thousands of dollars in restitution in the process. I hired David Maletta. We went to court and destroyed Billy and his best friend/roommate Taylor who were trying to extort me and ruin my life. In Arizona there is a 3.5% chance you’ll get all charges dropped because of how hard the state is on crime but we pulled it off and I still have a clean record to this day.
MJ Walsh - Google Review
“I would give them more stars, but the option is not there”
Best divorce lawyers in Arizona, hands down. Timothy Hintz handled my divorce, and as a father, I have my son and our house. I would give them more stars, but the option is not there. His paralegal Jennifer Bone is extremely competent, and the whole team is very friendly. Took a big weight off, having them behind me.
Joseph A. - Google Review
“The calm in the middle of my storm…”
I recently consulted with Darin after my wife filed for divorce. He was referred to me by a friend whom I very much trust. Darin was the antithesis of the first two attorneys I consulted (who were matter-of-fact and had very little empathy about the fact that I was struggling emotionally with what was transpiring). From the first few minutes of speaking with Darin, it was obvious that he was very knowledgeable and skilled with divorce and family matters. While that was most important to me, the thing that made the difference was his calming, logical, and empathetic approach. He took the time to listen and empathize with me. He took the time to understand what I wanted to achieve through this process and laid out my options. After the consultation, I knew he would be my attorney if I had to pull the trigger. I, ultimately, didn’t have to engage Darin’s services due to a reconciliation with my wife. I hope I never have to go through that process again. However, if I do, I know beyond a shadow of a doubt who I will be hiring to represent me…Darin R. Colburn. Darin, thank you for caring and being more than an attorney.
Frank - AVVO Review
“He fights for his clients like no one I have ever seen”
David Maletta is the absolute best trial attorney in the state of Arizona. He is a kind, emphatic, and extremely patient person. As an attorney, he is prepared, aggressive, and extremely skilled. He is not afraid to go to trial and fight for his clients, like other attorneys that just plead their clients to the original charges. When he is in trial, he flips a switch and goes from a nice guy to a killing machine. He fights for his clients like no one I have ever seen. Watching him do a cross-examination is exhilarating because he is so good it’s scary.
Patricia Bevins - Google Review
“Very professional, very empathetic, and very responsive to all the issues.”
I had the opportunity to work with Darin during a very troublesome time in my life. As a family attorney, I found him to be very professional, very empathetic, and very responsive to all the issues I faced. I would recommend him to anyone without a second thought. Thank you, Darin!
Gary C. - Google Review
“Responsive, sympathetic, professional, patient, and kind.”
On one of the worst and most surreal nights of my life (do not EVER get a DUI people!) I was lucky enough to find my way to Tim Hintze. Being in Phoenix for the Thanksgiving holiday from out of town, and after spending the evening with family, I ended up spending the night in jail.
Tim turned one of the worst experiences in my life into “it could have been so much worse!” Working with him from a different state, he covered the bases & paperwork, showed up for me in court, gave me numerous connections to muck my way through the system, and held my hand the whole way.
I cannot imagine how much worse this experience could have been, and thanks to Tim, I didn’t need to. He was responsive, sympathetic, professional, patient, and kind throughout the long process, drawn out by many months due to Covid.
Keep Tim’s number handy and in your contacts in the event you are ever in the sorry position to need a DUI lawyer!
Holly Weber - Google Review
“Tim was absolutely amazing and worked diligently”
I had an incident and was given the catch-all charge. There wasn’t really anything I could do by myself to get out of it. Tim was absolutely amazing and worked diligently to ensure that I would have the best possible outcome from my case. Which he successfully achieved! As of right now, I am on the path to having my case fully dismissed. A couple of things that really helped me through this process was that Tim did an amazing job at answering my questions. He was available almost anytime and would respond promptly when he got my emails. He was also very approachable and comforting to be around while we had in person meetings and especially when I was at the court house. I would trust him and the company he works for with any other cases in the future, and as of right now, they will be my first choice if I need a lawyer in the future.
Dylan - AVVO Review
“This was the best possible outcome, great price, and fast.”
Darin helped me with a complex family law issue involving ownership of multiple businesses and other assets. He was able to structure a win-win that wasn’t only better than I thought was possible but that protected the business I had built. Above and beyond that, he did it with great customer service and character – which really matters to me. This was the best possible outcome, great price, and fast.
David R. - Google Review
“There is NOBODY I would rather have defending me than David”
I hired David Maletta and it was the best decision of my life. His knowledge, genuine interest, overall attitude, and ability to connect with people is incomparable. I could talk about all of this at length. I COULD do all of that, but that wouldn’t do David justice. He first and foremost demonstrates his interest and genuine care for his client. Being in uncharted territory with a criminal charge and nowhere to turn, David’s presence and personality put all nerves at ease. I went through a jury trial with David beside me. The trial ran for 3 days and I spent a significant amount of time with David one-on-one. During this stressful time, he wanted to hear my input and thoughts on everything. David was incredible from the first day I met him. Not only is he a great attorney, but he is also a great person who cares about people and finding justice for his clients. He connects to the human side of people. I can’t put into words how much David cares about the individual in a case. When it comes to the courtroom, there is NOBODY I would rather have defending me than David.