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, our DUI defense lawyer, Alan J. Levine, will investigate your case, including the types of and manner in which field sobriety tests like the HGN test were administered. 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 of three standardized field sobriety so-called tests used by the police in Georgia to help determine whether a driver is under the unlawful influence of alcohol or drugs. 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.
How is the HGN Test Performed?
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 they must be properly instructed to look at a stimulus, like a pen, a light, or the tip of their finger, and follow that stimulus with both eyes while the officer moves the stimulus back and forth across the driver's field of vision.
The officer, who is not a medical expert let alone an eye doctor, attempts to assess the driver's eyes while moving the this stimulus from side to side. HGN evaluations are very technical. Proper administration involves specific requirements on the speed the stimulus is moved, the path it takes, and its height and distance from the driver's face.
The HGN evaluation is meant to measure the involuntary jerking of the driver's eye – known as nystagmus. But there are many reasons a person may display nystagmus. Yet police officers are taught, and a jury will be instructed, that a driver with a high blood alcohol concentration (BAC) may exhibit this nystagmus (involuntary jerking of the eyes) as the driver gazes 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.
Three Major Clues of Intoxication
Police look for three different "clues" when administering the HGN assessment. Each eye is assessed for these three clues, so there are actually a total of six possible HGN indicators of intoxication. These indicators must come in pairs being observed in both eyes. If there are an odd number of indicators, that means there may be medical issues with the driver's eyes.
Notwithstanding the above, if the officer determines four clues exist, that is supposed to indicate 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 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 known as lack of smooth pursuit.
- Clue 2 involves nystagmus in the eyes when they gaze as far as possible to the right or left – in this case, there is what is called 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 the stimulus be moved at approximately this speed, most officers move the stimulus two times too fast.
Ways to Challenge the HGN Test in Georgia
HGN tests can be challenged effectively by arguing against their reliability (these tests are highly subjective) or proving improper administration of the test (these tests require following strict and specific technical procedures). Also, these tests can be challenged based on matters not associated with the test itself, but matters related to the driver or to the environment.
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. A former DUI Court prosecutor, Alan is experienced investigating and reviewing the results of your HGN test and challenge it accordingly.
Contact Cobb County DUI Defense Attorney Alan J. Levine Today
Field sobriety tests are a way police officers gather probable cause to arrest you for DUI charges. These tests, however, are rarely conducted in accordance with regulations and are 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.
