Virginia DUI Field Sobriety Tests

Field sobriety tests are the roadside exercises police officers use to evaluate impairment during a DUI investigation. In Virginia, these tests often include the walk-and-turn, one-leg stand, and an eye test called the horizontal gaze nystagmus (HGN). People frequently assume these tests are “pass/fail,” but in practice they are observational tools: an officer looks for specific cues and uses those observations to decide whether to continue the investigation, request a breath test, or make an arrest. Performance can be affected by many non-alcohol factors, including anxiety, fatigue, medical conditions, uneven pavement, weather, footwear, age, and injuries. This page explains what field sobriety tests are, how they are used, why results can be misleading, and how they fit into a DUI case. For chemical testing issues, see our breath and blood test guide. For refusal issues, see our refusal page.

What Field Sobriety Tests Are Used in Virginia DUI Stops

During a DUI stop, officers commonly rely on a set of standardized field sobriety tests that were designed to be administered in a consistent way. The most frequently cited tests are the walk-and-turn, the one-leg stand, and the HGN eye test. Officers may also use additional exercises that are not standardized, such as reciting the alphabet, counting, or other divided-attention tasks. The key point is that these tests are not measuring blood alcohol concentration (BAC). They are meant to assess coordination, divided attention, and certain eye movements that may be consistent with impairment. In practice, the tests are often used as part of an “overall observations” narrative that includes driving behavior, odor, speech, balance, and admissions. Because these exercises can be performed on the roadside under stressful conditions, the context matters: lighting, traffic, uneven ground, and the officer’s instructions can influence performance. If your case involves these tests, it is important to know which tests were given and how they were administered.

Horizontal Gaze Nystagmus (HGN): The Eye Test

The HGN test is an eye test where an officer asks the person to follow a stimulus (often a pen or fingertip) while the officer observes the eyes for certain movements. Officers may describe “nystagmus,” which refers to involuntary jerking of the eyes, and they may record a number of “clues” they believe they observed. People often assume the HGN test is purely scientific, but the reliability of any HGN result depends heavily on how the test is administered, the person’s medical and vision history, and whether the officer followed standardized procedures. Certain conditions—such as head injuries, neurological issues, some medications, fatigue, or eye problems—can affect eye movements. Lighting, the distance and speed of the stimulus, and the officer’s training can also matter. HGN is also different from chemical testing: it does not produce a BAC number and is generally presented as one observation among many. If HGN is a central issue in your case, the details of administration and documentation often become critical in evaluating what the test result actually means.

Walk-and-Turn: Divided Attention on the Roadside

The walk-and-turn test is designed to evaluate balance and divided attention. Typically, an officer instructs the person to take a series of heel-to-toe steps along a line, turn in a specific way, and return. The officer may look for specific “clues,” such as stepping off the line, missing heel-to-toe contact, using arms for balance, starting too soon, stopping during the test, or taking an incorrect number of steps. In real-world settings, many factors can affect performance even when a person is not impaired. Uneven pavement, poor lighting, traffic distractions, rain or cold, footwear, and physical limitations can all matter. The test also depends on clear instructions; confusion or misunderstanding can be recorded as a “clue.” Because the walk-and-turn is both physical and cognitive, stress and anxiety can also have an effect. If your case includes this test, it is helpful to identify where it was performed, what instructions were given, whether there is body-worn camera video, and whether any physical or environmental factors were present that could explain the officer’s observations.

One-Leg Stand: Balance and Timing Factors

The one-leg stand test typically requires a person to raise one foot and hold it up while counting for a set period of time. Officers may look for “clues” such as swaying, hopping, putting the foot down, using arms for balance, or inability to maintain position. This test can be particularly affected by non-alcohol factors. Balance varies widely between individuals, and issues like ankle or knee injuries, back problems, inner ear conditions, age, weight, and fatigue can impact performance. Roadside conditions also matter—gravel, slopes, uneven pavement, and wind can make the test more difficult. The timing and instructions matter as well; a test administered with unclear instructions or inconsistent timing may not be comparable to a standardized version. Because the one-leg stand is physically demanding for many people, results can sometimes reflect physical limitations more than impairment. If video exists, it often provides important context that cannot be captured by a brief written summary in a police report. Understanding the setting and the instructions is crucial for evaluating this test fairly.

Common Reasons Field Sobriety Test Results Can Be Misleading

Field sobriety tests are performed under stressful, imperfect conditions, and they are not a direct measurement of BAC. Many people perform worse because they are nervous, overwhelmed, or confused by instructions. Others have medical conditions that affect coordination or eye movement. Environmental factors such as cold weather, rain, uneven ground, and traffic noise can also make performance harder. Footwear and clothing can affect balance, and lighting can affect visibility. Another issue is the “confirmation bias” problem: once an officer suspects impairment, normal mistakes may be interpreted as impairment clues. Documentation is also imperfect. Reports often summarize “clues” without capturing the full context, and non-standardized tests may be described in ways that sound more scientific than they are. Body-worn camera video, when available, can be one of the most important pieces of evidence because it shows the instructions, conditions, and actual performance. The defense perspective is typically to examine whether the tests were administered correctly, whether the observed “clues” are reliable, and whether other explanations fit the facts. Context can matter as much as performance.

How Field Sobriety Tests Fit Into a Virginia DUI Case

Field sobriety tests are commonly used to justify the next steps in a DUI investigation, including a request for a preliminary breath test, an arrest decision, or further questioning. They can also be used later in court as part of the officer’s explanation of probable cause and impairment observations. However, these tests are only one part of the evidence in many DUI cases. Chemical testing—breath or blood—often becomes a separate and highly technical issue. That is why it is helpful to separate the roadside testing questions from the chemical testing questions. If your case involves a breath machine, timing issues, or blood draw documentation, see our breath and blood test page. If a refusal is involved, see our refusal guide. For the step-by-step timeline of how DUI cases move through court, visit our DUI court process page. Understanding how these pieces fit together helps you evaluate what the Commonwealth will likely rely on and where the weaknesses may be.