What do field sobriety tests measure? Field sobriety tests (FSTs) are a set of standardized tests used by law enforcement officers to determine if a driver is under the influence of alcohol or drugs. These tests are designed to assess a person’s physical and mental abilities, which can be impaired by alcohol or drugs. By understanding what these tests measure, one can better appreciate their significance in the legal process and the challenges faced by individuals suspected of driving under the influence. In this article, we will explore the various aspects of field sobriety tests and their implications in the context of DUI investigations.
Field sobriety tests typically consist of three primary tests: the horizontal gaze nystagmus (HGN), the walk-and-turn test, and the one-leg stand test. Each of these tests measures different aspects of a person’s physical and cognitive abilities, providing insights into their level of impairment.
The Horizontal Gaze Nystagmus (HGN) Test
The HGN test evaluates the involuntary eye movements that occur when a person’s eyes are moved horizontally. When a person is under the influence of alcohol or drugs, these eye movements can become exaggerated or irregular. The officer observes the following three indicators of HGN:
1. Lack of smooth pursuit: The eyes do not follow a moving object smoothly.
2. Distorted or jerky eye movements: The eyes move in a jagged or uneven manner.
3. Onset of nystagmus before 45 degrees: The nystagmus begins to occur before the eyes have moved 45 degrees away from the center.
An officer can use these indicators to determine if a person is impaired by alcohol or drugs.
The Walk-and-Turn Test
The walk-and-turn test assesses a person’s balance, coordination, and ability to follow instructions. During this test, the officer asks the suspect to take nine steps in a straight line, turn around, and then return the same number of steps. The officer looks for the following clues of impairment:
1. Unable to maintain balance while listening to instructions: The suspect sways, uses their arms to balance, or hops.
2. Takes an incorrect number of steps: The suspect takes more or fewer than the required nine steps.
3. Unable to turn: The suspect loses balance or steps off the line while turning.
4. Unable to complete the test: The suspect is unable to complete the test due to physical impairment.
These clues can indicate that the suspect is impaired by alcohol or drugs.
The One-Leg Stand Test
The one-leg stand test evaluates a person’s balance and ability to maintain it. The suspect is asked to stand on one foot with the other raised, arms at their sides, and eyes closed. The officer observes the following clues of impairment:
1. Swaying while balancing: The suspect sways back and forth or from side to side.
2. Using arms to balance: The suspect uses their arms to maintain balance.
3. Hopping: The suspect hops to maintain balance.
4. Unable to maintain balance for 30 seconds: The suspect is unable to maintain balance for the required 30 seconds.
These clues can indicate that the suspect is impaired by alcohol or drugs.
Challenges and Limitations
While field sobriety tests are widely used in DUI investigations, they are not without challenges and limitations. Factors such as age, fitness level, and medical conditions can affect a person’s performance on these tests. Additionally, the accuracy of field sobriety tests can be influenced by the officer’s administration and interpretation of the results. As a result, it is crucial for individuals facing DUI charges to consult with an experienced attorney who can challenge the validity of these tests and protect their rights.
In conclusion, field sobriety tests measure a person’s physical and cognitive abilities, providing insights into their level of impairment. Understanding what these tests measure can help individuals better navigate the legal process and challenge the validity of the results if necessary.
