Updated: Jan 8, 2019
“Follow the tip of my finger with your eyes and your eyes only.”
During the HGN, the officer moves his finger or another stimulus around in front of your face while he looks at your eyes. What he’s looking for is an involuntary jerking or stuttering motion in your eye which can be caused by alcohol or certain controlled substances. The theory behind the HGN is that having a certain amount of alcohol or certain drugs in your system will cause that involuntary jittering, which is known as nystagmus.
There are six different clues that can be present on the HGN. Up to three can be seen in each eye, for a total of six. Having only one eye changes the game a bit.
The clues that officers look for during the HGN test are:
1. Lack of smooth pursuit,
2. Distinct and sustained nystagmus at maximum deviation, and
3. Onset of nystagmus prior to 45 degrees.
There are a ton of ways to attack the HGN test that was performed in your case, even if the officer says that he or she saw all six clues.
Three of the Most Common Issues with HGN
1. The officer had his blue lights on during the HGN.
Even the most recent field sobriety manual warns officers that nystagmus can be caused by strobe lights. This is known as optokinetic nystagmus. If the officer’s blue strobe lights were on during this test, we may have an argument that the nystagmus was actually caused by the officer’s own negligence!
2. The officer performed the HGN too quickly or slowly.
Each pass that an officer makes in front of your face during the HGN test is supposed to take a certain amount of time. If the timing of the test is substantially off, we may have an issue. One potential issue is “fatigue nystagmus,” which may be caused when your eyes fixate on one point at maximum deviation for too long. If an HGN test takes too long to complete, that may mean even more clues caused by the officer!
3. The officer failed to check your eyes before the HGN.
Again, the most recent version of the manual teaches that officers should screen for resting nystagmus and equal tracking of your eyes before he begins the HGN, rather than just launching into the examination.
If the officer has not checked for a pre-existing medical condition—if he has not checked to make sure that someone’s eyes react properly to begin with—can he even say that his results are valid?
A Final Word On Field Testing
By no means is the proceeding information an exhaustive account of all the ways that your officer’s field sobriety results can be attacked, and only an experienced DWI attorney can tell you how your performance on the test can best be interpreted.
I am a strong proponent of the common-sense observation that every case is unique. Every case comes packaged with its own set of facts out of which we get to cobble our defense. In many cases, the unique combination of facts will allow a good defense attorney to make arguments that would be virtually impossible on any other case! That’s why it’s so important for a good DWI attorney to have completely internalized the field test, it’s goals, and the policy behind it. Your attorney’s knowledge of the tests should be automatic. You have to live and breath the fundamentals, so that you can work on the art of defending each individual case rather than the science of the general field testing principles. You cannot focus on artistic flourishes at trial or during negotiations without first mastering the fundamentals.
The field sobriety test is by no means the end-all of your case. There are many other factors that play into your defense. To name just a few, a good DWI attorney will want to look at all the following before making a final analysis of your case:
1. How you were driving.
2. How you sounded on video.
3. Statements that you made to the officer.
4. The result of any portable breath test.
5. Any breath test result obtained at the station, and how to get around a >.08 result.
6. Whether any in-custody questioning was done, whether Miranda warnings were given.
If you have any questions about how field testing was done in your case, give me a call at 479-871-9602 to schedule a meeting.
 The actual instruction is supposed to be much more involved than that.
 Hazard lights on? Cars buzzing by quickly on the highway at night?
 Keep in mind that these are also arguments that your attorney can make at trial, not statements of law. It is ultimately up to the judge or jury to determine how to interpret the officer’s testimony, knowledge of the field tests, and your performance.