Key Takeaways
- Field sobriety tests (FSTs) are key tools in DUI investigations, but are not always accurate.
- Physical, environmental, and psychological factors can impact FST results.
- Legal challenges to FSTs focus on the administration of tests and individual circumstances.
- Awareness of FST limitations is vital for effective DUI defense.
Introduction
During traffic stops, law enforcement officers routinely employ field sobriety tests (FSTs) to gauge whether a driver is impaired by alcohol or drugs. The results of these tests contribute to the establishment of probable cause for arrests and form a crucial part of DUI cases. However, the accuracy and reliability of field sobriety testing have been hotly debated, especially given their impact on a person’s legal standing. When facing allegations of impaired driving, understanding the intricacies of FSTs is critical, especially for individuals and legal professionals working on DUI defense strategies.
Field Sobriety Tests (FSTs) are administered by law enforcement to assess physical and cognitive impairment, aiming to measure coordination, attention, and instruction following. While intended to be objective, FST outcomes can be affected by human error, subjective judgment, or external factors, leading to potential inaccuracies. Courts consider FST results in DUI arrests for reasonable suspicion and probable cause, making their reliability a frequent point of contention in legal proceedings. Factors beyond substance influence, such as medical conditions or nervousness, can yield unreliable results. The scientific and legal communities debate the consistency of FSTs as indicators of impairment, with research noting variations in officer administration and interpretation, which are further complicated by differing jurisdictional reporting practices.
Common Field Sobriety Tests
The National Highway Traffic Safety Administration (NHTSA) has established three primary field sobriety tests considered “standardized” for law enforcement use across the country. These are:
- Horizontal Gaze Nystagmus (HGN): This test involves an officer asking the driver to follow a small object, such as a pen or finger, with their eyes. The officer looks for involuntary jerking (nystagmus) of the eyeball—a phenomenon that can be exaggerated by alcohol consumption.
- Walk-and-Turn: The driver is instructed to take nine heel-to-toe steps along a straight line, turn on one foot, and return in the same manner. Officers look for signs like losing balance, stepping off the line, or inability to follow directions as potential indicators of impairment.
- One-Leg Stand: The subject must raise one foot about six inches off the ground and maintain balance while counting aloud until told to stop, typically for about 30 seconds. Swaying, hopping, or using arms to balance may be construed as evidence of intoxication.
While these tests are designed to identify clues of impairment, the interpretation of results remains subjective. Different officers may record the same performance in varying ways, and nerves or physical limitations can significantly impact the outcomes.
Factors Affecting Test Accuracy
Field sobriety tests are not administered in a vacuum, and many variables can influence their accuracy:
- Medical Conditions: Individuals with health conditions such as inner ear disorders, neurological impairment, arthritis, or recent injuries may exhibit impaired balance or coordination even in the absence of intoxication.
- Environmental Factors: The side of the road at night is rarely an ideal test environment. Sloped or uneven pavement, poor lighting, inclement weather, or distracting noise can compromise a person’s ability to perform well regardless of sobriety.
- Nervousness and Psychological Factors: Being pulled over by the police is stressful for most people. Anxiety and heightened nerves can lead to mistakes unrelated to alcohol or drug intake.
Even for individuals in good health and ideal environmental conditions, there is room for error and misinterpretation. False positives can cause unnecessary legal consequences for otherwise sober drivers, while false negatives may allow impaired drivers to continue on the road.
Legal Implications and Challenges
Police often cite field sobriety tests as primary evidence for probable cause in DUI arrests. However, their subjective elements mean results can be—and usually are—contested in court. Defense attorneys will frequently scrutinize several aspects of the stop and the administration of FSTs, including:
- Whether the officer was properly trained and adhered to NHTSA protocols for each test.
- If adverse weather, poor lighting, or uneven ground could explain the individual’s difficulties during the tests.
- The existence of any medical or physiological conditions that might produce impaired results.
- Whether language barriers or a lack of clear instructions undermined the individual’s ability to comply.
Proper documentation and a thorough understanding of these nuances help lawyers mount effective challenges to FST results. Challenging the validity of field sobriety testing is particularly important given that these tests are just one component of the larger investigative process, and jury members may assign considerable weight to their outcomes.
Conclusion
Field sobriety tests remain a staple of DUI enforcement, yet their accuracy and fairness continue to be subject to scrutiny. A comprehensive and informed DUI defense requires careful consideration of factors that may impair test reliability. By understanding the standard procedures, variables impacting accuracy, and legal strategies to contest FST results, both defendants and attorneys are better prepared to protect their rights and ensure due process.
As laws and law enforcement tactics continue to evolve, staying up to date on the best practices and research surrounding field sobriety tests is essential. For those seeking further information, the Nolo legal encyclopedia provides additional guidance on DUI cases and defense strategies.
