In North Carolina, field sobriety tests are an integral part of law enforcement’s toolkit for detecting impaired driving. These tests help officers evaluate a driver's physical coordination, balance, and behavior to determine if there's probable cause for a DUI arrest. Alcohol screening tests are largely governed by N.C. Gen. Stat. § 20-16.3. The most used field sobriety tests in the state are the Horizontal Gaze Nystagmus (HGN) test, the walk-and-turn, and the one-leg stand. When administered properly, these tests can provide critical evidence in a DUI case, but they must be approached with care.
Tests sponsored by the National Highway Traffic Safety Administration show that the HGN test is the most reliable (77 percent), followed by the walk-and-turn test (68 percent), and the one-leg-stand test (65 percent).
The Horizontal Gaze Nystagmus test
Among the field sobriety tests, the HGNtest holds a significant role in identifying impairment. The HGN test involves the officer instructing the driver to follow an object, typically a pen or flashlight, with their eyes. The officer looks for involuntary jerking movements in the driver’s eyes, which are referred to as nystagmus. This jerking is a natural physiological response that becomes more pronounced under the influence.
Nystagmus occurs when a person’s eye moves beyond a certain point of focus. A driver who is under the influence may display exaggerated or pronounced eye jerking as the alcohol affects their ability to control their eye movements. The test’s reliability comes from its scientific basis: research has shown a strong correlation between these involuntary eye movements and impairment. However, for the results of the HGN test to be valid in court, officers must meet certain procedural requirements, including proper training and adherence to standardized testing methods.
The use of the HGN test in North Carolina has been the subject of extensive legal scrutiny. The North Carolina Supreme Court in State v. Helms, 348 N.C. 578 held that HGN test results could only be admitted as evidence if a proper scientific foundation was established. This is done through expert testimony. Officers are required to testify about their training, the specific procedures they followed, and the results they observed. Without this foundational testimony, the test results may be excluded. This rule has now been codified under N.C. Gen. Stat. § 702.
Walk-and-turn and one-leg stand tests
Beyond the HGN test, the walk-and-turn and one-leg stand tests are commonly administered as part of the standard field sobriety test battery. These tests focus on the driver’s ability to follow instructions and maintain physical balance, difficult activities when someone is under the influence.
In the walk-and-turn test, the driver is asked to walk heel-to-toe along a straight line, turn, and return in the same manner. The test is designed to assess balance, coordination, and the ability to follow instructions.
The one-leg stand test requires the driver to stand on one leg while counting out loud for a period. Impaired drivers often struggle with maintaining their balance and may be unable to perform the task as instructed. This test is particularly useful in assessing the driver’s coordination and balance.
Totality of circumstances and probable cause
It’s important to note that field sobriety tests do not operate in isolation. In many cases, officers use these tests in conjunction with other observations, such as the smell of alcohol, bloodshot eyes, slurred speech, and erratic driving behavior. Together, these factors create a totality of circumstances that officers rely on when determining probable cause for a DUI arrest.
North Carolina courts have reinforced that field sobriety tests, when considered alongside other signs of impairment, could provide the necessary probable cause to arrest a driver for driving under the influence. (See State v. Woolard, 385 N.C. 560; State v. Parisi, 372 N.C. 639).
An experienced attorney can help
Whether you’re facing a DUI charge or simply want to understand the process, the role of field sobriety tests in North Carolina law is a critical aspect of ensuring justice in impaired driving cases. The attorneys at Jetton & Meredith can help you understand your rights and legal options. If you need help, call today.