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Exploring Field Sobriety Tests: Reliability and Challenges


Field sobriety tests (FSTs) are evaluations conducted during DWI stops to assess a driver's potential intoxication. These assessments involve a series of divided attention tasks, requiring the driver to focus on multiple elements simultaneously. During these tests, an individual's mental and physical capabilities are tested as they are asked to perform tasks that demand coordination, balance, and concentration.

FSTs are designed to be challenging, particularly when an individual's mental clarity and physical coordination are compromised. The difficulty in performing FSTs accurately when under the influence makes them a valuable tool for law enforcement officers to determine impairment levels. When a driver exhibits poor performance on these tests, it provides officers with probable cause to suspect driving under the influence, justifying further legal action.

It's important to note that FSTs are an initial step in the assessment process. While they can provide valuable insight into a driver's level of impairment, they are not definitive proof of intoxication. Instead, they contribute to the overall evidence that law enforcement uses to decide whether to make an arrest.

At Norwood & Norwood, P.A., our team delivers aggressive defense in Northwest Arkansas. Contact us at (479) 235-4600 today.

Types of Field Sobriety Tests

FSTs encompass a range of assessments to evaluate an individual's potential impairment due to alcohol consumption.

The three standardized FSTs established by the National Highway Traffic Safety Administration are the:

  • Horizontal Gaze Nystagmus (HGN)
  • Walk-and-Turn (WAT)
  • One-Leg Stand (OLS)

It's worth noting that officers may also administer non-standardized tests to assess impairment in certain situations.

Each of these tests aims to gauge a person's command over their mental, physical, and physiological faculties, which are vital for safe driving. In the WAT, the driver must walk in a straight line, heel-to-toe, turn on one foot, and then walk back while adhering to specific instructions. This test assesses physical capabilities, particularly balance and coordination. Similarly, the OLS evaluates a driver's ability to maintain balance while standing on one leg for a designated period.

The HGN involves tracking a stimulus (often a pen or light) with the eyes as it moves horizontally. This test assesses involuntary jerking of the eyes, called nystagmus, which can become more pronounced when a person is under the influence of alcohol. The sooner the jerking motion occurs as the eyes follow the stimulus, the higher the likelihood of impairment.

A critical aspect of FSTs is their standardized nature, ensuring consistent evaluation across different officers and jurisdictions. This standardization minimizes subjectivity and enhances the reliability of the tests as indicators of potential impairment.

Factors Affecting Reliability

The standardized FSTs are accepted indicators of impairment.

Field validation tests place the accuracy of each assessment as follows:

  • 88% for the HGN
  • 79% for the WAT
  • 83% for the OLS

While field validation studies have demonstrated the tests' reliability under ideal conditions, several factors can impact their accuracy and consistency.

Environmental Conditions

Environmental conditions play a significant role in affecting the outcomes of FSTs. Adverse weather, poor lighting, or uneven surfaces can impede a driver's performance, resulting in potentially misleading results.

Officer Training

The variability in officer training and execution of FSTs can contribute to inconsistencies. Officers who haven't received adequate training or who do not administer the tests precisely according to established procedures can introduce subjectivity and inaccuracies into the assessment process.

Individual Factors

Individual factors also come into play, as medical conditions, fatigue, and nervousness can influence FST outcomes. Certain medical issues can affect an individual's ability to perform balance-related tasks, while tiredness and anxiety can impact concentration and coordination.

Importantly, individuals stopped for DWI are not legally obligated to participate in FSTs and can refuse without facing penalties. However, even if someone declines to take part in the tests, officers can rely on other indicators of impairment to establish probable cause for an arrest. This could include observations of slurred speech, the odor of alcohol, or erratic driving behavior.

As such, while FSTs provide valuable insights into potential intoxication, they are just one part of the puzzle law enforcement uses to determine whether someone is driving under the influence.

Safeguard Your Rights by Consulting a Legal Representative

Staying informed about your rights during sobriety testing is vital. If you face a DWI stop, understand that you can decline participation in FSTs. This knowledge empowers you to make informed decisions that align with your best interests.

For those seeking legal assistance in Northwest Arkansas, Norwood & Norwood, P.A. is here to help. Our experienced team challenges evidence in DWI matters, ensuring that our clients’ rights are protected and their cases thoroughly examined.

To schedule a consultation, please call (479) 235-4600 or contact us online today.