Horizontal Gaze Nystagmus (HGN) test is one of three standardized field sobriety tests (SFSTs) validated by the National Highway Traffic Safety Administration (NHTSA). It is also a test that police in all Georgia counties, including Cobb, administer frequently during traffic stops when intoxicated driving is suspected. Though the NHTSA recognizes the HGN as a test that can indicate impairment, this test is not fool-proof. In fact, it has its disadvantages, which make admitting it as evidence problematic.
In Georgia, DUI defense lawyer Alan J. Levine’s investigation of cases includes how the police officer administered field sobriety tests like HGN. At Georgia DUI & Criminal Defense, we use our skills and resources to ensure you receive the best representation possible. Contact us at 770-870-4994 to schedule a free consultation and learn more about how we will help you fight your DUI charge in Cobb or any other county in Georgia.
What is a Horizontal Gaze Nystagmus Test?
The Horizontal Gaze Nystagmus test is one evaluation Georgia police use to decide if a driver is DUI. The other two are the “walk and turn” and the “one leg stand”. But police officers are rarely, if ever, trained ophthalmologists. Indeed, in 17 years doing this, we’ve never encountered a police officer with adequate medical training to really understand what they were doing beyond their police DUI courses. We’re still waiting to meet our first doctor turned police officer in court.
The officer’s HGN performance
The officer conducting the HGN test should provide clear verbal instructions to the driver. The police officer should tell the driver to stand still, place their hands to the side, and keep their head still. They need to medically clear the driver as well. Then, if the officer does their part correctly, the driver is instructed to look at a stimulus. The stimulus will be a pen, a light, or the tip of the police officer’s finger. The officer tells the driver to follow the stimulus with both eyes as the stimulus moves back and forth across the driver’s field of vision.
It is unlikely the officer is a medical expert, let alone an eye doctor. Nevertheless, they will attempt to assess the driver’s eyes while moving the stimulus from side to side. HGN evaluations are very technical. To properly administer the HGN evalution, the stimulus moves at a consistent, specified rate of speed. Also, the stimulus takes a specified path. Lastly, the height and distance of the stimulus from the driver’s face are during the HGN are specified by NHTSA procedures.
If done correctly, the HGN evaluation ascertains the involuntary jerking of the driver’s eye – known as nystagmus. But there are many reasons a person may display nystagmus. Yet, during their training, police officers learn, and juries instructed, that a driver with a high blood alcohol concentration (BAC) exhibits nystagmus (involuntary jerking of the eyes) as they gaze toward the side while following the stimulus. And, when there are no complicating variables and done just right, this may indeed be the case. But more often then not, there are complicating variables, and the officer often makes mistakes.
Horizontal Gaze Nystagmus Intoxication Clues
Police look for three different “clues” when administering the HGN assessment. The officer assesses each eye for them. So, there are actually a total of six possible HGN indicators of intoxication. Properly performed, HGN clues come in pairs. When the officer sees a clue in the right eye, they should observe it in the left, too. If there are an odd number of indicators, that means there may be medical issues with the driver’s eyes.
Also, if the officer determines a driver displays four clues, supposedly the driver’s blood alcohol content (BAC) level is above 0.08 percent. And without understanding the science behind this, at a motion to suppress or trial, the police officer may attempt to testify to this supposed correlation between HGN indicators and BAC.
The three HGN clues are as follows:
- Clue 1 occurs when the driver is unable to follow the stimulus on a horizontal path without there being nystagmus. This is lack of smooth pursuit.
- Clue 2 involves nystagmus in the eyes when they gaze as far as possible to the right or left. This is distinct and sustained nystagmus at maximum deviation.
- Clue 3 involves the onset of nystagmus in the eyes before 45 degrees, or what the NHTSA terms onset of nystagmus prior to 45 degrees.
To perform the HGN assessment correctly, each clue requires the officer to use proper pacing when moving the stimulus. For example, the movement of the stimulus to determine both equal tracking (part of the pre-HGN medical clearance) and lack of smooth pursuit should be approximately two seconds from before the driver’s nose out to the side, and then two seconds back from the side to before the driver’s nose. And, while there is some wiggle room in the NHTSA instructions by directing that the stimulus move at approximately this speed, most officers move the stimulus two times too fast.
Ways to Challenge the HGN Test in Georgia
Attacking HGN’s reliability (it’s highly subjective) or proving improper administration (it must follow strict, specific technical procedures) are means to challenge the assessment. Other issues related to the driver or to the environment may be suitable areas for attacking HGN.
Common Challenges to the HGN Test
- Unreliable based on police officer’s subjective estimations and preconceived notions
- Unreliable based on police officer’s failure to administer the test properly
- Unreliable based on external factors
Common External Causes of Failed HGN Tests
- Bad weather
- Administered at night in darkness or during the day with a glaring sun
- Bad roads or other environmental issues
- Patrol car lights flashing or other lighting issues
- Driver’s pre-existing health issues or medications, like ear disorders, eye disorders, head injury or brain damage, excessive amounts of caffeine, antihistamines, barbiturates, illness like the flu or vertigo
Keep in mind that there are more than 38 non-alcohol-related causes for nystagmus, and each of these can lead to a failed HGN test.
The HGN evaluation is faulty. Your DUI defense attorney, Alan J. Levine, is able to highlight these weaknesses when they exist, and then create reasonable doubt in the prosecution’s case against you. Alan is a former DUI Court prosecutor. Alan’s experience includeed investigating and reviewing HGN assessments, and challenge them accordingly.
Contact Cobb County DUI Defense Attorney Alan J. Levine Today
HGN field sobriety tests are part of how police officers gather probable cause to arrest driver’s for DUI. However, officers seldom conduct them in accordance with regulations. They’re faulty given their subjective nature.
At Georgia DUI & Criminal Defense, DUI defense lawyer Alan J. Levine, with his 17 years of experience as a prosecutor and defense lawyer, knows how to prepare and challenge the state’s so-called standardized field sobriety tests (SFSTs) like the HGN assessment. To learn more about how Alan can help your DUI case, contact him by filling out the online form – or calling 770-870-4994 to schedule a free consultation.