Pennsylvania Criminal and Family Law Blog | Tibbott & Richardson

June 20th is International Nystagmus Day. Nystagmus is a complex visual impairment, characterized by involuntary eye movements, affecting focus and depth perception. In the context of Driving Under the Influence cases, the presence of nystagmus can be related to alcohol usage.

What is Nystagmus?

Nystagmus is a condition that affects the vision. This condition is similar to a muscle twitch which causes your eyes to move around up and down, side to side, or in a circle. While your eyes are twitching and moving around in this uncontrolled manner, your vision is impaired. Nystagmus can cause you to become dizzy, lose your balance, or impair your depth perception.

Who Gets Nystagmus?

Most cases of nystagmus occur in young children. Nystagmus that appears later in life may be the result of multiple sclerosis or a traumatic brain injury such as a stroke. Other causes include the presence of an inner ear infection, severe astigmatism, side effects of certain medications, or alcoholism.

How Does Alcohol Consumption Affect Nystagmus?

According to the National Highway Traffic Safety Administration, intoxicants can increase nystagmus or the amount of involuntary eye twitching. Alcohol consumption or consumption of other “central nervous system depressants” hinders the ability to control eye muscles correctly. This results in the twitching or jerking of the eyes.
Alcohol can cause two types of nystagmus, the first being alcohol gaze nystagmus, which includes the Horizontal Gaze Nystagmus test, and the second is a positional alcohol nystagmus.

What is the Horizontal Gaze Nystagmus test?

Standard Field Sobriety Tests

Police officers use various field sobriety tests to determine whether or not someone is impaired. Some of these tests include the alphabet test (recite the alphabet from A to Z or from a certain letter to a certain letter, or backwards); the finger-to-nose test (stand straight up with feet together, tilt head back as far as possible and then touch nose with both left and right index fingers); and the coin pick-up test (the officer places a number of coins around the operator, who is then directed to squat, rest an elbow on his or her knee and pick up each coin in a certain order and place them in the opposite hand). However, there are only three tests that qualify for standardization in Pennsylvania.

Standardized Field Sobriety Tests were developed by the National Highway Traffic Safety Administration in the mid seventies to establish a reliable and consistent methodology for evaluating intoxication. NHTSA determined that three tests, if administered in accordance with NHTSA guidelines, could accurately predict whether a person is under the influence such that the person cannot safely drive. The three field sobriety tests approved by NHTSA are the Horizontal Gaze Nystagmus “HGN” test (better known as follow my finger), the Walk-and-Turn test, and the One-Leg Stand test. These field sobriety tests consist of two distinct phases: the instructional phase and the performance phase. The officer will introduce each test and explain in detail how it is to be performed.

Horizontal Gaze Nystagmus “HGN” Test

In the horizontal gaze nystagmus test, the officer asks the driver to keep his or her head still and follow an object such as a pen with only the eyes. The officer moves the object back and forth in front of the operator and looks for nystagmus. Some studies suggest that early onset of nystagmus is an indicator of alcohol intoxication.The alcohol that a person allegedly consumes results in poor motor coordination and slow reflexes. Thus, the nervous system, which controls eye movement, cannot cause the eye to roll smoothly; instead, it lags behind and jerks.

Admissibility of HGN Tests

Although it is considered to be a standard field sobriety test, Pennsylvania courts have repeatedly held that the results of the HGN are inadmissible at trial. It can only be used in establishing probable cause to give police a reason to arrest you. Because the HGN test is not able to be captured on the police officer’s dash camera, the court will not be able to review your performance to determine if your eyeballs were shaking. Conversely, you will not be able to offer any extrinsic evidence at the time of your preliminary hearing or trial to prove that you did perform the test satisfactorily. The National Highway Traffic Safety Administration testing determined that the HGN only yields the correct result approximately 77% of the time.

Did You Pass Your HGN Test?

Failing the HGN and other standard field sobriety tests is not a definitive indication of intoxication. Individuals with diagnosed medical conditions impacting vision, balance, coordination, or hearing may have problems with these field sobriety tests. Additionally, adverse weather conditions can also affect test results. However, the failure of a field sobriety test does give a police officer probable cause for an arrest. You would then need to decide if you will submit to a chemical test or face the penalties of a refusal under implied consent laws which usually lead to a one-year revocation of your driver’s license.

Remember, field sobriety tests like the HGN are conducted to assist the police officer in developing a case and gathering evidence against you. You have the right to politely refuse to participate in any field sobriety testing. Should you decide to participate in field sobriety testing, it is important to obtain an attorney who can carefully examine field sobriety test evidence. In some instances, police officers do not administer the test in full compliance with NHTSA guidelines by using improper scoring criteria, incorrectly instructing the driver on how to perform the test, or not using the standard methodology in performing the tests. These details are especially important at the time of trial so that a jury understands the weaknesses of field sobriety testing.

Drunk driving defense in Pennsylvania requires a set of technical and highly specialized skills that includes intensive training on examining standard field sobriety testing. At Tibbott & Richardson, we have this specific training and not only understand all the moving parts of a DUI charge in Pennsylvania, but also how each part can affect your future.

Pennsylvania Criminal and Family Law Blog | Tibbott & Richardson

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